HOST SELECTION, OWPOSITION BEHAVIOLTR, AND INTER- … · 2020-04-07 · ABSTRACT Host selection, oviposition behaviour. and inter- and intra-specific competition in the white- spoued

HOST SELECTION, OWPOSITION BEHAVIOLTR, AND INTER- AM) INTRA-SPECIFIC COMPETITION IN THE WHITE-SPOTTED PINE

SAWYER BEETLE, MONOCHAMUS SCUTELLA TUS (SAY) (COLEOPTERA: CERAMBY CIDAE)

Shawna Michelle Peddle

A thesis submitted in conformity with the requirements for the degree of Master of Science in Forestry

Graduate Faculîy of Forestry University of Toronto

(8 Copyright by Shawna Michelle Peddle ZOO0

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FACULR OF FORESTRY University of Toronto

DEPARTMENTAL ORAL EXAMINATION FOR THE DEGREE OF MASTER OF SCIENCE IN FORESTRY

Examination of Ms. Shawna M. PEDDLE

q Examination Chair's Signature: G - *n-

u

We approve this thesis and afirm that it meets the departmental oral examination requirements set down for the degree of Master of Science in Forestry.

J Examination Cornmittee:

* l , Af%J% 1

L

Date: L bt - ' L ~ Z G C O

ABSTRACT

Host selection, oviposition behaviour. and inter- and intra-specific competition in the white- spoued pine sawyer beetle. Monocliamils scutellatus (Say) (Coleoptera: Cerambycidae)

S hawna Michelle Peddle, M.Sc.F.. 2000 Graduate Faculty of Forestry University of Toronto

This snidy examined host selection, competition. and oviposition behaviour in the

white-spotted pine sawyer beetle. Monochamus scutellatus (Say ). Adul t beetles were

anracted to mating and oviposition sites by host volatiles. nirpentine and a-pinene. Ethanol. a

by-product of plant decomposition. was determined to have no effect on host selection. Other

members of the phloem-feeding p i l d had little or no effect on M. scurellatus oviposition and

larval success. Niche partitioning. through spatial or temporal segregation. allowed co-

existence by guild members Pissodes nemorensis Germ. and Ips pini (Say). The sequence of

behaviour in M. scutellatus oviposition uas generally stereotypic and uniform. The presence

of eggs from another fernale deterred oviposition, while the presence of larvae or her own

eggs had a less deterrent effect. Site selection. dorninance in the @Id, and avoidance of other

progeny are al1 adaptive for M. scutellarus in securing resources for developing offspring,

and reducing competition for these resources.

ACKNOWLEDGEMENTS 1 would like to thank my supervison. Dr. Peter de Groot, of the Canadian Forest

Service Great Lakes Forestry Centre in Sault Ste. Marie, Ontario, and Dr. Sandy Smith. of

the Faculty of Foresuy. University of Toronto. Peter, thank you for the project and funding.

as well as your never-wavenng professional. academic and personal support. You have been

a grear mentor, and friend. You taught me how to be a scientist; 1 hope a hundred more

students are as fomnate. Sandy, thank you for the academic and thesis suppon for revisions

of the final venions of the thesis, and for the open door. 1 would also like to thank the third

member of my supervisory cornmittee, Dr. Tim Myles of the Faculty of Fores-. University

of Toronto, for his interest. for his contribution, and for teaching me the finer points of

decornposi tion.

1 would like to thank the Canadian Forest Service for full project funding. as well as

the Faculty of Forestq. University of Toronto, for funding through the Louis Nouilillo

Graduate Fellowship in Forestry, and Faculty bursaries.

I would like to thank Reg Non, of the CFS in Sault Ste. Marie. for his endless

patience and personality in the field and lab, as well as for reviewing final versions of the

thesis. 1 wouId also Iike to thank f f S surnrner students Shauna Dunn, Kevin McCracken,

Melissa Montgomery, and Cheryl Momson, for able bodies and constant humour in the field.

1 would Wce to thank Kelly Kirkland, Stephanie Erb, and Gary White, for their fnendship,

support and laughter. Finally, I would like to thank my parents. This is for you.

TABLE OF CONTENTS

TABLE OF COhmNTS ............... ................ ................................................................................................... IV .................... LET OF TABLES ...... .. ............................ ................................................................................. VI

....... .......... LIST OF FIGURES ". ....wt..............l...-...-...............w.. " .....o...U.. ........................... ....-.. ............. V ii

...................... CH,AlTER ONE: INTRODUCTION ..~..........mH.-............................................+..o.+..*........... . 9

................................................................ .......................... GESERL\L B IOLOGY OF LONGHORNED BEETLES t,, 9 .................................. B r o m OF MONOCHAMUS S C ~ E U A T U S (SAY) ........................... ............................... 9

.......................................................................................................... ............................. Idenrification ....,. 9 ............................................................................................................................... Economic Significance IO

LE HISTORY OF THE GENUS MUNOCHAMUS ................................................................................................. 1 1 .................................................................................................................. LE HETORY OF M . SCWELW~JS 12

........................................................................................................ ûviposirion and Larval Development 13 ............................................................................................................. PREWOUS WORK ON M . SCUEKATUS 13

......................................................................................................... G n c n w ~ E c o m ~ OF M . SCUT;ELLATUS 15 ........................................................................................................................................... Guild Srructure 15

............................................................................................................................................ Host-finding 17 ............................................................................................................................... Chiposition Behnviour 19

OBEcmVEs ..................................................................................................................................................... 21

CEhUTER TWO: CEIEMICAL ECOLOGY OF HOST m E SELECTION BY M O X O C H M U S ..... SCUTEUTUS (SAY) (COLEOPTERA: CERAMBYCIDAE). .O..-... ........................... 23

IhTRODUCïION .......................................................................................................................................... 23 M4TERIALS AND METHODS .................................................................................................................... 26

Sm@ Sires .................................................................................................................................................. 26 ..................... Eiperimenrs I & 2. Amacriveness of turpentine. ethunof and a-pinene ,.........nn.....nnn..... 36

Erperimenrs 3 & 4 . Cornparison of varying reZease rates of a-pinene .................................................... 27 Traps ............... .... .............................................................................................................................. 27

........................................................................................................................ Lpyout of Traps .............. .... 29 ..................................................................................................................................... Statistical Analysis 29

..................................................................................................................... RESULTS AND DISCUSSION 30 ................................................................................... Amctiveness of turpen fine. ethonul and a-puiene 30

Attraction to varying reiease rares of U-pinene ..................................................... 33 CONCLUSION ...............*........................................................*.................................................................... 37

CHAPTER THREE: INFLUENCE OF INTER-SPECIFIC COMPETITION AND NI- PARTKIONING ON OVIPOSITION BY M O N O C E ' S SCUTELLATüS SAY (COLEOPTERA: CERAMiBYCIDAE) .--.- ........-........---- 38

........................................................................................................................................ IhX'RODUCTION 38 .................................................................................................................... MATERIALS AND METHODS 41

kperimenr I .......................................................................................................................................... 41 Erperiment 2 ................................................................ 43 ........................................................................ ErpeRment 3 ................... ........ ....................................................................................................... 44

RESULTS ..................................... ,.. .................................................................................................. 4 6 Erperîment I ........................................................................................................................................ 46 Erpehent 2 ................................. ....... ................................................................................ 48

................... Ekperiment 3 ............. ...................................................................................................... 50 S I O N ........................................................................................................................................ 5 3

......................................................................................................... Temporal Segregorion of Oviposition 5 3 .................................................................................................... Spatial Segregation of Oviposirion Sites 51 ........... Effect of Sun h o s u r e on Site Selecrion ..... ................................................................................ 56

....................................................................................................................................... Hast Tree Species 56 Monality Factors ....................................................................................................................................... 59

CONCLUSION ............................................................................................................................................... 60

CHAPTER FOUR: OVIPOSITlON BEHAVIOUR AND INTRA-SPECIFlC COMPETITION OF MONOCHAMUS S C U T E U T U S (SAY) (COLEOPTERA: CERAMBYCIDAE) ................*....... .. 62

INTRODUCTION .......................................................................................................................................... 62 .................................................................................................................... MATERIALS AND METHODS 65

. . ................................................................................................................................ Oviposrtron behaviour 65 ................................................................................................................................................ Choice tests 66

.......................................................................................................... Preparusion of bolts for choice tests 66 ........................ Determination of the presence of eggs for choice tests ... ....................................... 68 . . ........................................................................................................................... ..... Statutical anuiysir ... 68

..................................................................................................................... RESULTS AND DISCUSSION 70 . . . û ~ t ~ o ~ t t t ~ f f behviaur ............................................................................................................................... 70

I

................................................................................................................... Effect of eggs on sire selection 75 ................................................................................................................ Effecr of lunwe on sire selecrion 77

Effect of eggs front the same or o diflerenr fernale on site selection ....................................................... 79 CONCLUSION ............................................................................................................................................... 82

............... .............................**....*.**.*..........*.*....~............................. CHAPTER F m : SUMM-4RY .....+... 84

REFERENCES ...... ................m.......M.... W.* . ....-HH.....~.. ..O .... ....*.............................................. 88

LIST OF TABLES TABLE 3-1. M m N MJMBER OF M. S C ~ ~ T U S OVIPOSITION SC-S. SCARS COhTX[h'LXG OVIPOSïïIOh' PLLfGS,

ENTRANCE HOtES [NT0 THE SAPWOOD. AND GALLERY SURFACE .UEA FOR LrNC.i\GED RED AND WHITE P M toGS LN EXCLUSlON CAGE STüDIES, 1998, WELLS TOWNSHIP, ONTARIO. .................................................. 47

TABLE 3-2. NUMBER OF M. SCUïELUTUS OVIWSiTION SCARS AND P. lVEMORENSIS PUP.LU. CELLS FOUND I?! ZONES AROUND THE CIRCUMFERENCE OF RED AND WHlïE PiNE LOGS PUCED ON THE CROUND 16 JUN T'HROUGH 1 1 AUG 1998, ~ K w O O D TOWNSHIP, ONTARIO. THE CIRCUMFERENCE OFTHE LOGS N'AS DIVIDED JXTO E Q U A i ZONES BASED ON A CiûCK FACE (FIG. 3- I A). ................................ .. ........................................... 49

TABLE 4- 1. BEHAVIOURAL SEQUENCE ASSOCIATEL) WITH 58 OVIPOSITlON EVEbiTS Bt' FEM.-UT M. SCLi7EU4TU.S WDER FIEIl) (N= f O) AND WORATORY CONDfiïONS (~=48) fh' 1 998 AND 1999. ...................................... 74

TABE 4-2. RESPONSE OF FEMALE M. SCUTELLATUS TO BOLTS WITH OR WlTHOUT EGGS OR U R V A E FROM HERSELF OR A DFFERENT FEMALE DURiNG LABORATORY CHOICETESTS. 1998. ~......~~....~......................-.-.......-........ 76

TULE 4-3. NUMBER OF OVlPOSITION SCARS AND EGGS DEPOSITED US BOLTS PRESLMED TO F E M U M. SCüTELWTUS BEnzEs DURING CHOICE TESTS US 1999. .............................................................................. 80

LIST OF FIGURES

FIGURE 2-1. CROSS-VANE TRAPS L'SED FOR COUECTION OF BEETLES. 5 AUG MROCGH 3 SEPT. 1999, LAWLOR .................................................................................................................................. TOWNSHIP, ONTARIO 38

FrGURE 2-2. RESPONSE OF M U XVD FEMALE M. SCtTTELMTU.5 BEETLES TO TRAPS BA~TED WlTH: A ) ETHXNOL

PLUS TURPENTINE. ETHANOL. TURPESTKNT. AND 8 L W K CONTFZOLTRWS: AXD B) TURPENTWE, CL-PINENE, AND BLANK CONTROLTRAPS, 2 JLS THROUGH 25 AUG, 1998. W U TON%SH~P, ONTARIO. BARS WITH THE SAME tFITER ARE NOT SIGNCFIC.ASïiY DfFFEREM AT P=0.05 (ANOVA WITH TUKEY'S TEST). THERE WERE NO S I G N ï F ï C M DEFERENCES i f >o.os) [.r; W M B E R OF MALES AND F E ! ! I m CAUGHT FOR AiiY OF

'1 . 1 ....................................................................................... ......................... THE ABOVE TREA'IMENTS.. .,..-. -.

FIGURE 2-3. RUATIONSHIP BFMZEE: RULASE U T E S OF Cr-PINENE AND fRAP CATCH OF FEMALE IV+ S C W ï U S ADULTS, 5 AUG THROUGH 3 S m . 1999, LAWLOR TOWNSHIP. OhTMUO. SLOPE OF REGRESSION LiNE 1S SIGNmC.WïlI ' DWERENT FROM ZERO (N=60 TRAPS. ~'=0.110, Pd.010). .............. 34

FIGURE 2-4. RUATIONSHIP B m E E H RELTASE R A m OF U-PINENE AND TRAP CATCH OF M U M. SCUTELUTUS AfIULTS, 5 AUG THROUGH 3 S m . 1999, LAWLOR TOWNSHP, ONTARIO. SLOPE OF REGRESSION UNE IS NOT SIGNmCANTLY DIFFEREM FROM ZERO (N= 60 TRAPS, R'=o.o~o~. P=0.12 1 ) ..................................... 33

FIGURE 2-5. RELATIONSHIP B m E E & REEASE RATES OF CL-PNENE AND TRAP CATCH OF FEÀÀALE M. hfU'B?ATOR ADULTS, 5 AUG IHROUGH 3 SEPII 1999. ~ W L O R TOWNSHIP. OhTTAR10. SLOPE OF REGRESSION LiST IS

...................................... NOT SIGNIF~CANTLY D E F E R E X FROM ZERO (N=60 TRAPS. R'=O.O~O 1. P a . 185) 35

FIGURE 2-6. &L.AT~ONSH~P BET'6ZE.V RELEASE RATES OF CC-PMENE .WD TRAP CATCH OF MALE M. MUATOR ADULTS, 5 AUG ï?iROUGH 3 SEPT, 1999. ~ W L O R TOWNSHCP. OhTARIO. SLOPE OF REGRESSION UEIE IS SIGNiFiCANnu D[FFEREhTT FROM ZERO (N=60 TRAPS. R'=O.O~S?. k0.034. ............................................ 35

FIGURE 3- 1: DIAGRAMMATIC REPREISPr7AnON O F THE CROSS-SECIIONAL DIVISIOS OF THE CIRCUMFERENCE OF SîUüY LOGS NT0 6 EQUAL ZONES .............................................................................................................. 33

FIGURE 3-2. NUMBER OF IPs PIN1 ADULT'S COtLEcfED IN CAGES [h' THE LhS FROM LWCAGED RED AND WHIT'E PME i û G S COtLECED 9 JUPE THROUGH 18 .ALE, f 998 FROM FIELD STTES iK WELLS TOWNSHIP, ONTARIO. .... 47

FIGURE 3-3. CLMJLATNE EMERGENCE (h' CAGES Ih' THE M. 25 JUNE THROUGH 14 AUG, 1998. OF ADULT IPS PfNf FROM U N C A W RED AND WHITE PiNE tOûS FROM FlELD S K E S IN WEUS TOWNSHIP, ONTARIO. THERE WAS A SIGNIFICANT DIFFE?EYCE BETWEEN T O T U OF [PS EMERGING FROM RED AND W H m PiNE LOGS AT P = 0.05 (TWO-SAMPLE T-TEST). .................................................................................................................... 48

FIGURE 3-4. CUMUL4TIVE W E R (SE) OF M. SCUTELLATUS OVIPOSITfON SCARS ON WHlTE PiNE LOGS [N SUN AND SHADE CONDITIONS, EXAMINES 29 JUN THROUGH 3 f AUG, 1999, WELU TOWNSH~P, ONTARIO.

WAS A SIGNFICANT DïFERE3CE BEïWEEN CUMUfATIVE TOTALS UNDER SUN AND SHADE AT P = ....................................................................................................................... 0.05 ('IWO-SAMPLE T-TEST). SO

FIGURE 3-5. CUMULATIVE NUMBER (SE) OF P. NEMORENSIS OVlPOSlTION HOLES ON WHITE P1NE LOGS IN SUN AND SHADE CONDii'iONS, EXAMINED 39 JUN THROUGH 3 1 AUG, 1999, WELU TOWNSHIP, ONTARIO.

wAS NO SIGNIFICA\T DIFFERENCE BEïWEEN CUMUUTNE TOTALS UNDER SUN AND SHADE AT P = ....................................................................................................................... 0.05 (TWO-SAMPE T - m ) . 5 1

FIGURE 3-6. NUMBER OF NEW M. SCüiEUAlflS OVIPOSiTION S W S EXCAVATED ON WiTE PiNE L m , 29 JUN THROUGH 3 1 AUG, 1999, AT FIELD SITES IN WELU TOWNSHIP, ONTARIO ..................... ,.. .... .,.,..- .......... 5 1

FIGURE 3-7. NWER OF NEW P. NEMORENSIS OVIPOSITiON HOLES Oh' WHITE P m IBGS, 29 kW THROUGH 3 1 ............ AUG, 1999, AT FELD S ï E S h' WELLS TOWNSHIP, ONTARIO. .. ........................ ,. .................... 52

vii

FIGLRE 4- 1. SEQUENCE OF COhlPONEXTS OF OVIPOSiTION BEHAVIOUR BY F E 3 I . U M. SCb7Ett-t TL'S BEETLES, BAsED ON 27 FEMALES OBSERVED O E R A TOT AL OF 35 HOURS IN f 998 ASû 1999. .................................. 7 1

FIGURE 3-2. COhlPONENTs OF THE OVIPOSITION BEHAVIOURAL SEQUENCE OF M. SCüiUL4Tt'S. .&?XI PERCEiiTAGE OF TOTiU. TIME DEVOTED TO EACH PORTION OFTHE SEQüENCE. THE SEQL'E..CE BEGAY N'RH H'.4LWG, .ANID CONCLUDED WlTH THE INSERTION OF MANDIBLES N T 0 THE SCAR ....................................................... 72

F~GURE 4-3, PERCENTAGE OFTOTAi OVIPOSITION BY M. SCU7EUATU.S FEMALES O S EACH OF TEST .%\XI C0E;fROL BOLTS DURING M O R A T O R Y CHOICE TESTS. THOSE COLUMNS DENOTED BI' .Lh: A S T E R S ( = \ HALT

SIGh'IFICAKnY DIFFERE!!T h W S AT P = 0.05 (WO S W P E T-TEST). .................................................. 78

F!CV?S 4 4 . nvP0SlTlON SUCCESS ON RED P M BOLTS BY F E M U M. SCUTIlLATL3 BEETLES DCRING LABORATORY CHOICE TESTS. PRE-TEST REFERS TO OVIPOSITION ON BOLTS BY FEMALES PRIOR TO CHOICE TESTS. SAME FEMALE REFERS TO OVlPOSlTION Oh' A BOLT CONTAINING EûGS FROM THE TEST =\!ALE. .*'il DFFERENï FEMALE REFERS TO EGGS UID ON h BOLT CONTAMING EGGS FROM A DiFFEREST F E h l U . l ' E R E IS A SIGNIFICAKi DiFFERENCE BEntrEEh' OVIPOSiTION SUCCESS ON BOLTS DURWG THE CHOICE TEST

........................ ................................, .AT P= 0.05. DENOTED BY AN ASTERIS (*) (TWO-SUIPLE T-TEST). ..,. 8 1

Chapter One: Introduction

General Biology of Longhorned Beetles Longhomed beetles are members of the family Cerambycidae. with 20.000 descnbed

species throughout the world i Yanega. 1996). In North America. the adults are generally

short-lived. with the majonty of feeding and development occumng in the larval stages

(Craighead, 1973). Adult beetles feed on pollen. fungi. foliage and Young twigs, whereas

l m a e feed on living, dead and decaying woody and herbaceous plant rnateriai (Craighead.

1923). Size in the majoriry of species is sexudly dimorphic. with males being smaller and

having longer antennae than femdes. Most cerambycids are capable of sound production in

the adult and/or larval stages 1Yanega 1996). Many specics of this family are of great

economic and ecologicd importance. feeding in or on healthy and dead plant marerial.

Biology of Monochamus scutellatus (Say) A number of authon have described the pneral biology of iMonochamns scutellatus

i Say). This chapter will provide an overview of the literature on the species. with some detail

on topics that will be covered in subsequent chapters.

Identification

Taxonomy

Class Insecta

Farnil y Ceramb y cidae

Subfamily Lamiinae

Tribe Monochamini

Genus Monochamus

S pecies scutellarus ( S ay )

Life Stages

M. scutellatus is one of the largest Coleoptera found in the boreal forest. The egg is

;a. 3 mm in lensh, elongare. cyiindncal and slightly flattened. srnooth and shining white.

Eggs are deposited sin& in scars excavated under the bark of conifers. The lamie measure

up to 2.5 cm in length. and up to 0.75 cm wide at the thorax. Four land instars have been

documented. Pupae average about 2.5 cm in lengh. and are found in pupal ceils ca. 5 mm

from the bark surface at the end of a feeding tunnel.

Adult beetles average 1.9-2.5 cm in len-&. and 0.5-0.75 cm in width. Adults of both

sexes are black. with females generally being iighter in appexance due to pubescence on the

dytra. Both sexes have a small white spot on the scutellum. berween the elyua. The species

exhibits sexual dimorphism - male anrennae are twice body lenkgth. while female antennd

lrnpth is approximately that of the body (Rose. 1937: Wilson. 1962a: Yanega. 1996).

Economic Significance Sorne species of Monochamrts are vectors of Bursaphelenchus .rylophili<s (Steiner and

Buhrer) Xickle. the causarive agent of pine wilt disease in Asia and North Amerka (Dwinell.

1997). This nematode is not pathogenic ro native pines. but kills exotic pines in North

Amerka, and is a major monality factor for native pines in Japan (Dwinell. 1997).

Nematodes enter the uees through adult feeding wounds made by Monochamus. The

nematodes then mature and feed upon tree parenchyma cells, resulting in wilt symptoms and

quick death of the tree (Dwinell, 1997). M i l e a phoretic relationship has been demonstrated

for M. carolinensis (Olivier), M. altematus Hope. and M. salruarius (Gebler) (Akbulut and

Linit, 1999a; Shibata, 1984; and Jikmaru et al.. 1994), there has been no evidence to support

potential phoresis by M. scutellatzts.

In North Amenca. prirnarily in b o r d regions. M. scutellatris has a great economic

impact through lamal feeding on cut logs left in the field or at lumberyards. Monochamus

beetles are considered to be one of the most destructive pests of coniferous logs in Canada

(Morley. 1939). Adult feeding upon twigs and young foliage may result in girdling of the

branch. but rarely damages living uees. L m a l heanwood feeding damases logs. with a

subsequent reduction in timber value. Lmae can tunnel an average of 7.5 cm into the wood.

and it has been estimared that Iarvai feeding cm reduce wood volume by up to 5 9 (Cerezke.

1975: Wilson. 1962b). These tunnels ma? resulr in increased handling time at sawmill

operations. and rejection of logs for panicular uses. such as for power poles (Cerezke. 1975).

L m a l tunnels also facilitate envy into the wood bg Sap rot and stain fungi. which discolour

and desuoy the wood. reducing value by as much as 33 8 (-Wilson. 1962a).

L a n d mnneling. while resulting in an economic loss for cut logs. also plays an

important ecoiogical role. Larvae consume great amounts of woody material. structurally

weakening the wood. Tunneling aiso allows for envance of rot fungî. as well as other wood-

boring insects. accelerating decomposition of woody material in the forest ecosystern. The

economic implications of this feeding have pnerally ovenhadowed examination of the

ecologicai role of these beetles.

Life History of the Genus Monochamus Al1 species of Monochamus have the same general attack sequence on dead and dying

coniferous species. Females are attracted to host voIatiles released by dead and dyin, = uees.

Pheromone attraction has only been documented in one species, M. airemarus (Kim et al..

1992). Beeties undeqo a period of maniration feeding after emergence from pupal cells in

logs. Females and males are found on logs during day or night, depending on species, with

mating occurring on the log surface (Rose. 1957). Afier mating, females deposit eggs singly

in scan excavated in the bark surface. Larvae moult through four lama1 instars. emeqing the

following spring from a pupal chamber just under the bark surface. Adults feed on foliage

until reproductive1 y mature. and then mate.

Life History of M. scutellatus M. scutellatus is found throughout North America, with the exception of the central

United States (Yaneza. 1996). Adult beetles emeqe from logs in the spring. and undergo

maturation feeding upon new conifer twigs and foliage (Wilson. 1962a). Afier 7-10 days of

feeding, mating generaily occurs in early aftemoon. with oviposition immediately following

(Rose. 1957: Hughes and Hughes. 1987). There has been no documentation of long-range

pheromone attraction in M. scutellurus. suggesting that mate-finding on the surface of the log

occurs by some other factor. such as short-range pheromones. visual cues. or acoustic ïues.

Male reproductive success in M. scurellatus is associated with body size. and abilil). ro

defend the log resource until arrival of the female (Hughes. 1981). Resource defrnse

polygyny is seen, in which a male defends high quality areas of fallen logs until arrival of a

female. He then defends the female from other males while she is on the surface of the log

(Hughes and Hughes. 1985). This allows the male to ensure oviposition in a high-qualit!

area, and the half-mount mate-parding position assumed throughout the interspened

copulation/oviposition period ensures the fernale will deposit eggs that he has fenilized. Mate

selection by the female may be based on mating ability of the male, and the quality of [he

resource he defends. Females are likely to choose larger males, a factor that cm affect firness

of her offspring (Hughes and Hughes, 1985).

Oviposition and Larval Development M. scurellarus females preferentially oviposit in dead and dying conifers (Wilson.

1962a). After mating, a female will excavate a scar in the bark surface with her mandibles ro

deposit her eggs. Scars excavated before mating are generally empry (Rose. 1957). Eggs are

deposired sin& in scars. and lantae hatch within 9-14 days (Rose. 1957). L m a e consume

the egg casing. and begin ro tunnei in the phioem iaysr. ingeaihg phlocm zlid cxïd%ün;.

After approximately 1-3 weeks. larvae moult to the second instar. and continue feeding in the

phloem layer, sconng this area under the bark (Rose, 1957).

FoIlowin_g a funher 2-3 weeks of feeding. the larvae moult to the third instar and

tunnel into the sapwood and heanwood of the log. Feeding in this and the founh instar

creates a characteristic "UV* shaped tunnel (Wilson. 1962a). In southem regions. the life cycle

is one Far, with lmae over-wintering as a pre-pupa and puparing and emerging the

following spring (Wilson. 1962a). In northern regions. larvae ma!. have a one-year lifecycle

as above. or a two-year cycle. These over-winter as third instar lan*ae in tunnels in the wood

and spend the next summer feeding, then moult to fourth instar the following fall <Rose,

1957). These founh instar larvae ninnel to Ca. 5 mm h m the outer bark surface. and

consmct a pupai cell, plugging the end of the tunnel with wood fibres Wlson . 1961a).

Larvae pupate and adults emerge from holes cut in the bark at the end of these pupal cells the

following spring.

Previous work on M. scutellatus Rose (1957) gave an overview of the general life history of M. scurellarus on baisam

fir, defining the number of Iarvai instars, and the Iife-cycle of the species in Ontario.

Characteristics of damage in standing and downed trees was exarnined by Cerezke (1975.

1977), Wilson (1962ab) and Raske (1975). Potentid rnitigation measures to remove l o g

from cutting sites. or stonge options to prevent or reduce the amount of damage to logs have

been suggested (Cerezke. 1975: Wilson. 1962a.b: Posr and Werner. 1988). The contriburion

of M. scrttellatus to death and decomposition of fire-killed rrees has also been examinrd

(Gardiner. 1957).

Reproductive behaviour of M. scutellarus has been esamined. particulxi y dealing

with male mating success. Fernales chose larger males. resulting in an increase in the rate of

oviposition. as females moved more slowly and were more likely to be receptive to

copulation with a larger male (Hughes and Hughes, 1985). L-er males were able to arrract

and keep fernales by defending higher quality areas on the log. such as those with a larger

circumference (Hughes and Hughes. 1983). Males that were able to s a r d females for longer

penods of tirne also had increased reproductive success. 3s fernales were depositing eggs that

the garding male had fertilized (Hughes. 198 1).

Members of this species often fight to severe injury or death in contests for resources.

so a larger male would be better suited to defend the female and the resource from smaller

males in combat (Hughes and Hughes, 1987). There is also competirion between M.

scurellatus and related species in the same habitat, such M. noratus (Hughes and Hughes.

1987). Combat over resources was generaily avoided if the opposing beetle was the larger M.

notarus. The longer antennae of male M. scurellatus beetles have also been exarnined. to

determine their evolutionary significance and role in combat and communication (Hughes,

1979).

While there has been extensive work on the reproductive behaviour of M. scutellarus.

there has been no examination of the oviposition behaviour of the species. The role of

cornpetition in oviposition site selection also has not been determined. Rose (1957) and

others have provided the general lifecycle and ecological role of the species. However. the

role of M. scurellarus in the phloem-feeding guild. and inrcractions under bark has yer to be

cietermined. Dyer and Seabrook ( 1978) suggested that oviposition site selection by female M.

scurellntus beetles is mediated by chernical cues. such as nost volatiles. However. the? were

not able to conclusively determine the role of these chemicals in host selection. No author

has demonstrated the role of chemicals. as pheromones produced by insects. or allomones

released from host plants. in oviposition site selection b y JI. scrîrellatiis.

General Ecology of M. scutellatus

Guild Structure Coleopteran community stnicture within dead ivood changes from initial colonizers.

such as the family Scolsidae, to secondary attack b' borers of the families Cerambycidae

and Buprestidae. These are followed by predaceous families juch as Staphylinidae and

Cicinidelidae. and finail' to fungivorous beetles such s thosc of the family Erotylidae

1 White. 1983). A variety of species arrive at the resource throughout the earliest stages of

decomposition. and community composition changes ivith time (Zhong and Schowalter.

1989).

In pine. the majonty of these insects are found in and under the bark, and most are

found in the earlier stages of decomposition (Howden and Vogt. 195 1). Thomas ( 1955)

found that a number of insects and other arthropods inhabit red pine (Pinus resinosa Ait.) and

white pine (P. srrobus L.) Iogging slash in northern Ontario. and rhat the successional pattern

of this community changes over urne with the degree of decay of wood.

Prïmary insects arrive fint, and ofien contribute to death of the tree in the process of

oviposition and larval development The first wave of colunizen may be atuacted to host

stimuli, with subsequent colonizers arriving in =mat numbers in response to pherornones

released by insects at the site (Brattii et al., 1998). Secondary arrivais at the tree are incapable

of killing the host. and are reliant upon some other agent to atrack and kill the healthy uee

(Gardiner. 1957). These species may not Ml the tree directly. but May hasten death, or

introduce pathogens that may result in decreased vigour and evenmal death of the uee.

A guild is defined as a group of species sharing the sarne habitat. and having similar

resource requirements and foraging strategies (Flarnm et al., 198: i. Insect families found in

decaying wood are genenlly di~ided into four guilds. each using the resource in a distinct

way: l ) phloem and sapwood borers: 2 ) fungus. frass. and detritus feeders: 3) parasites: and

4) predators (Thomas. 1955: Ramm et al.. 1989). M. sc~itellutiis is a phloem and sapwood

borer. a member of a guild utilizing fresh phloem and sapwood for larval development. Al1

are obligate feeders on phloem in the I m a l stages, with shallow feeden living entirely in the

phloem layer. causing no appreciable damage to the wood. Deep-boring species like M.

scitrellatus feed in both the phloem and sapwood. causing geat damage to the wood

(Gardiner, 1957).

Cornpetition between species in this two-dimensional feeding arena may be: 1 )

interference, or direct competition dirough tannibalism or predarion: or 2 ) exploitative. in

that one species excludes the other bj. utilizing the resource before arrival of the second

species (Byers. 1989). Memben of the phloem-feeding guild musr contend with competition

in order to maximize fitness and sunpival. Most memben of the p i l d are able to successfully

avoid competition h o u @ resource pmitioning, or spatial or temporal segreegation of feeding

and oviposition sites (Byers. 1989).

Host-finding Insect species use host plants as sites for feeding. mating. and oviposition. Host plant

availability is ofren temporally or spatially limited within an ecosysrem. This is particularly

m e for xylophagous insecrs. which require dead wood in a panicular stage of decomposition

for oviposition. These insects must be able to detect not only the appropriate host species. but

also the right stage of decomposition for oviposition.

Two hypotheses are used to explain host tree selection by wood-feeding insects. The

'pnmary attraction hyporhesis' postulates that beetles select a uee pnor to alightment. based

on a combination of visual and chernical cues. The 'random attack hypothesis' posrulates that

beetles randomly alight on 2 potential host tree. and accept or reject the host after m i v a l

(Brattli et al., 1998). Prim- attraction is mediated by a number of long-range chernicals

released from the host piant. detected by insects at a distance. Random attack relies on cues

that are detectable only after alightment. such as tactile or short-range chemical cues.

Random attack could result in lost time, because insects could land on a nurnber of uees

before finaily reaching n host suirable for feeding or 0\4position. Long-range chemical cues

would make host selection a much more efficient process, reducing the number of potential

landings before a suitable host is found.

Visual cues, including the o u t h e of a swarming mass of conspecifics. a vertical

object, or the silhouette of a particular tree species, are vital for host-finding in many insect

goups. These visual cues may result in location of a number of potential hosts. but cannot

give an indication of the status of the tree. Most plant-breeding insects must rely on chernical

stimuli to further narrow the search for an appropriate host plant These stimuli are ofien used

in combination with visual cues to make the site-selection process less time-consuming for

fernale beetles.

Chemical cues for host finding include host tree volatile semiochemicals, or

pheromones. both of which have an effect on the behaviour of insects that receive the signal.

These c m act as allomones, which benefit the emitter: kairomones. which benefit the

receiver: or synomones, which benefit both emitter and receiver (Hagan et ai.. 1981). Upon

reaching the host. chernotactic. tactile. gustatory or ovipositional cues may play a role. A

suite of cues allows an insect to find a suitable host, possibly in an area that contains

numerous sirnilar or conuadicrory cues. Generalist species are anracted to a variet? of hosts

and mes. whereas specialist insects. those that requise a specific host species or condition.

are anracted to a narrow range of cues.

.-Z number of scolytid beetle species rely on aggregation pheromones released by the

fint wave of colonizing insects to find a suirable host for rnating and oviposirion (Wood.

1982: Czokajlo and Teale. 1999: Billings. 1985; Brattli et al.. 1998). These pheromones can

serve as kairomones for inter-specific cornpetitors. giving a x y lophagous insec t information

on the host tree starus if both species require similar stages of death or decay.

Many wood-feeding beetles use chernical cues produced by the host itself for

selection. For those species that do not produce pheromones, or for initial insects aniving at a

host. host volatiles are a cue for orientation. Allelochemicals such as terpenes released by the

host plant can further narrow the host selection process, allowing a female to find a host for

feeding or oviposition. Branli et ai. (1998) determined that a variety of conifer-living beetles,

including bark beeties (Scolytidae). weevils (Curculionidae) and woodborers Cerambycidae)

used a combination of host volatiles andlor pheromones, and a number of species were able

to detect a suitable host tree in flight The use of host volatiles for attraction of conifer-

feeding weevils is well known (Rieske and Raffa, 199 1; Lindelow et al.. 1993; Hoffman et

al.. 1997: Tilles et ai., 1986), with most species being attracted to a specific conifer volatile

that allows them to find a suitable host tree. Due to the patchy distribution of suitable hosts.

most of these insect species are very specific in detectinn of chemical cues from the host.

which enables h e m CO eficiently find oviposition and feeding sires.

Oviposition Behaviour Cornpetition for resources occurs throughout the Iife of an insect. These resources

may include shelter, mates. and sites for feeding and oviposition. Hi$ population numbers

and limited resource availability result in competition. and ma- have a negative effect on

insects in a particular habitat. Avoidance of competition can lead ro increased suwival. and

increased fitness amongst progeny (Prokopy et al.. 19841. Successful foraging for

exploitable resources must avoid cornpetition. not only from members of the same species

i intra-specific competition). but also from different species that share the same niche (inter-

specific competition).

Parasitism and predation upon al1 life stages must also 'De avoiaed. while procunng

the highest quality and quantity of the resource. whether for aduh feeding or oviposition. The

search for a host may be influenced by a number of factors. inciuding chemical cues from the

resource itself. or from other insects utiIizing the resource. particularly chemically marked

areas that have been previously exploited by conspecifics (Prokopy et al.. 1984). Foraging by

= resource way of chemical cues from other insects may help reduce competition by preventin,

use by a nurnber of different individuals. This is particularly important in oviposition. as

progeny use the resource rnuch later for lamal deveiopment. Sire selecrion by females can

have a great effect on the survival of offspring, and avoidance of cornpetition at this stage

may increase size and robusuiess of offspring, thus increasing the fitness of the female.

One way to avoid competition is through resource partitioning to maximize resource

use without encounterîng other insects in the area There is a maximum density of individuals

that c m successfully exploit a resource wirhout detrimental effect upon any of the individuals

involved. Pmitioning of this resource. through chernical or physical means. rnay acr ro

reduce contact between individuals, and maintain a density belou cornpetitive thresholds.

Cues for avoidance of cornpetition may include o v i p o s i i o - d e pheromones. which act

intra-specifically to alert females to the presence of anorher egg in the immediate vicinity.

pheromones. and visual and tactile cues.

Oviposition behaviour in insects involves dl aspects of rgg-laying. including site

selection. site preparation. and eventual egg deposition. In species of Coleoptera that inhabit

wood. such as M. scutellatus. site preparation ofren involves excavaring a scar. and insening

the ovipositor for egg depoçition beneath the bark. Female behwiour in sile selection and

egg deposition greatly affects survival of offspring. as a poor oviposition site ma? adversely

affect feeding and development.

Oviposition behaviour has been studied in a nurnber of insect species. particularly

those that oviposit on fruit and foliage. such as Rhagoletis pomonella (Osten Sachen)

(Prokopy . 19731, and Hylema sp. (Zimmeman. 1 979). Female e gg-parasi tic Trichogranznia

chih ic Ishii wasps have been obsemed to discriminate between parasitized and non-

parasitized host larvae (Miura et al., 1994). and numerous other species use a variety of cues

to find their hosts, such as host odour in Leptopilina clacipes (Tumiinson et al.. 1993). Hosr

discrimination allows a female to provide the best possible environment for developing

larvae.

Optimal oviposition behaviour in phytophagous insects assumes that the reproductive

success or fitness of a female insect depends upon the success of a behavioural component in

that female during the oviposition process. The quality and suitability of oviposition sites

varies. A female, through behaviour modifications, must choose a suitable site in order to

maxirnize fitness of her progeny (Jaenike. 1978). As there is little or no parental care in most

species of insects, a female would concribute most CO survival of her progeny by choosing a

site rhat is protected from cornpetition. predators, and parasiroids. but also contains an

adequate supply of nutritious food. This results in behaviour leading to extensive selectivity

in host choice, maximizing success of progeny once oviposition is complete.

Factors affecting oviposition site selection prior to alightment on a host include host

volatiles. host plant size and shape. and pheromones. Of these. only pheromones. and

potenrially the presence of other insects. continue to have an affect on female behaviour upon

landing on the host. Numerous factors rnay influence female choice in site selection upori

amval ar a host. These may include bark thickness (Nakamura et al.. 1995b). presence of

other insects on the log surface. presence of eggs and/or lame (Anbutsu and Togashi.

1997a). or other s i p s of oviposition by conspecific females.

Larval survivai ma? be influenced by predators. parasitoids. and cornpetitors. and

naturd selection in development of host choice may be based on 'enemy-free space'. in

which survivai is potentially increased by the absence of these factors (Thompson. 1988 i . A

number of studies have determined that intenpecific competition has an effect on the

oviposition biology of insects (Shroeder. 1997: Prokopy et al., 1984). A femde rnust be able

to determine the presence and extent of threat from other insects before oviposition and

incorporate this into the behavioural sequence upon amival ai a suitable host.

Objectives Little is known about the process of oviposition site selection in M. scutellarus. There

is no documentation of pheromone production in this species, and the role of host chemicals

is unclear. Oviposition behaviour and the role of competition in site selection are also

unknown in this species. This thesis was initiated to provide further insight into the chemicai

ecology of host selecrion. niche dynamics of dl. scutellotris. and the sequence of behaviours

involved in oviposition. Chapter One provided a general ovenirw of what is known about

the species. as well as background information on the topics that were encountered in this

study. Chaprer Two provides an examination of the chernical ecology of host tree selecrion

for M. scutellants. Attraction to host volatiles. juch as rurpentine and a-pinene. and erhanol.

a natural decomposirion by-product, were examined for male and female beetles.

Chapter Three discusses inter-specific competirion within the phloem-feeding guild.

focussing on M. scutelZatus and two species that share the niche. the nonhem pine/deodar

weevil, Pissodes nemorerisis Germ.. and the pine engraver. Ips pini (Say). .Aspects of

temporal and spatial segregation that alloa. these species ro exploit the same limired

resources were examined. as well as the potenrial influence of insolation and host species on

oviposition site selection and lmal success. Chaprer Four rxpands on aspects of comperition

in site selection. dealing with intra-specific cornpetition in oviposition. The potential

influence of the presence of oviposition detemng pheromones and progeny under the bark

was examined. as was the sequence of events in oviposirion. Chapter Five presents

conciusions of these studies. and provides recommendations on how these results cm be used

in further studies and management of M. scutellatus. One overdl bibliography for the thesis

follows Chapter Five. Chapters Two through Four are presented in the format of journal

articles. to facilitate later publication of this work. As a result, there exists some duplication

and potential overlap in presentation of information and introductory and background

material. However, the results, discussions and conclusions of al1 chapters are distinct and

will be synthesized only in the final Chapter Five.

Chapter Two: Chernical ecology of host tree selection by Monochamus scutellatus (Say) (Coleoptera: Ceram bycidae)

INTRODUCTION

Monocham~s sc~rrellatrts ( S a y ) , the white-sponed pine sawyer beetle. is found

rhroughout North Amenca and is prevalent in the boreal forest of nonhern Ontario. Adults

feed on twigs and foliage of living pine trees. and females deposit e g s in scars excavated in

the bark of dead and dying conifer species. Larvae hatch to feed in the phloem layer under

the bark and evenniaily ninnel inro the heartwood. where they pupate and emerge in summer

either one or two yars later (Rose, 1957). Larval feeding tunnels degade lumber (Wilson.

1962a) and contnbure greatly to wood decomposition in the forest ecosystern.

Adult M. scurellarus beetles are known to be attracted to nirpentine. a combination of

various host volatile monorerpenes produced from distilled conifer oleoresin (Gardiner,

1957). Chenier and Philogene <, 1989a.b) determined that M. scurella~us beetles were attracted

to rurpentine and that rhis attraction was similar to that for a blend of monoterpenes.

including (Ç)-a-pinene. (-)+pinene, (t)-camphene, (2)-limonene. myrcene. and (+)-A-3-

carene. M. scureilatus was most srrongly amacted to commercial turpentine and (+)-a-

pinene, the major attractive constituent of nirpentine. Dyer and Seabrook (1978) also

suggested thar terpenes might be used for host selection by M. scurelZutus.

Attraction to turpentine has also been demonstrated in the related species M. ridlaror

(Fabricius) and M. carolinensis Olivier (Fatringer, 1985; Phillips et al.. 1988: Billings,

1985). Billings (1985) determined that the combination of nirpentine and Ips bark beetle

pheromones increased attraction to baited traps for M. titillator. Attraction to traps baited

M. al~ernatio Hope (Ikeda et al.. 1980). The highest number of 34. alternatr~s beetles were

attracted to baited traps approximating the monoterpene ~~aporization ratio from bait logs in

the field.

Ethanol is produced through rnicrobial respiration during decomposition of plant

materiai. Ethanol generally is not present in heaithy uees but car. be produced when a tree is

under stress (Sjodin et al.. 1989). or dunng anaerobic conditions I Kimmerer and Kozlowski.

1987). Ikeda et al. (1980) detected ethanol in conifers wirhin 3- 10 days of cutting, and these

lewls generally increase upon death. relative to the stage of dezomposition (Phillips et al..

1988). The number of M. scutellatus beetles collected at uaps bYred with ethanol alone was

similar to that for unbaited control traps (Chenier and Philogene. 1989a). Numbers of M.

carolinensis and M. ririllator collected at traps baited with ethaiiol alone were sipificantly

lejs than that caught at turpentine-baited traps (Phillips er al.. 1058: Fatzinger. 1985 1. These

resulü demonstrate that ethanol done is not highly effective in attraction for Monochamris

species. As ethanol is produced during decomposition of al1 plant material, attraction to

oenus- or wood-feeding beetles must be mediated by some other factor. particularly the =

species-specific host volatile chernicals released by the uee (BratrIi et al.. 1998).

Beetle attraction to monoterpenes such as a-pinene ma>- be synergized by ethanol,

with the additive attractive effect of the monoterpene and ethano1 being greater than that of

either of the iwo compounds alone (Tilles et al., 1986). A synergistic effect has been

demonstrated for M. scutellatus, with higher nurnbers at traps baited with a blend of

monoterpenes and ethanol than for monoterpenes alone (Chenier and Philopne. 1989a).

However, the same effect was not seen for a-pinene alone and edianol. as trap catches were

lower when compared to a-pinene alone (Chenier and Philogene, 1989a). A synergistic

effect has been demonstrated for turpentine and ethano1 in M. cnrdinensis and M. titi2Iator

(Fatzinger. 1985). Phillips et al. (1988) determined that while the effect was synergistic for

M. tirillator, it was not for M. carolinensis. This is ecologically significant in that a specific

ratio of ethanol and a-pinene may have to be detecred by a female before host selection.

While previous snidies have demonsrnted synergism berween a monoterpene blend

and ethanol, and commercial turpentine and ethanol for M. sc~irellarris. no study has

determined a synergistic effecr for a-pinene and ethanol for the species. No direct

cornparison has been made between attraction to nirpentine and one of its major constituenü.

a-pinene. for M. scurellarus. The studr undenaken by Chenier and Philogene ( 1989a) used

one release rate for each cornpound studied. and stated that smdl sarnple sizes could not lead

to a conclusion on the variation in attraction between ethanol and turpenrine. and ethûnol and

a monoterpene blend. No study on M. scurellarus has examined attraction to a variety of

ethanol and monoterpene release rares. which change in a natural situation as monoterpene

release slows and ethanol production increases upon death of a tree. The specific

combination that is most attractive to species of Monochumus has yet to be investigated.

This study was undertaken to expand upon the work of Chenier and Philogene

(1989a), to furrher examine the role of hosr volatiles in host uee selection for oviposition by

M. scutellatus. Trapping expenments were conducted in the field to compare the attractive

nature of turpentine and its major constituent a-pinene. Studies were aiso undenaken to

examine the influence of ethanol upon attraction, and verify if a synergistic effect was

present between ethanol and nirpentine. Finally, attraction to a range of a-pinene release

rates was examined to determine if an optimal release rate increased attraction by M.

scutellatus.

MATERIALS AND METHODS

Study Sites Four baited-trap expenments were conducted in 1995 and 1999 to determine the

anractiveness of turpentine. a-pinene and ethanol to M. scuteliarus. Experiments 1. 2 and 3

were conducted in a mixed conifer-hardwood forest located in Wells Township (46' 25' S.

83' 22' E), Ca. 40 km nonh of Thessalon. Ontario. Predominanr conifer species were manire

white pine, Pinus srrobus L.. red pine. P. resinosa Ait.. and white spmce. Picea gfaitca

(Moench) Voss. Experiment 1 was conducted in a recent jack pine (P. banhiana Lamb.)

clear-cut located in Lawlor Township (47' 05' N. 82' 50' E). c2. 140 km north of Thessalon.

Ontario.

Experiments 1 & 2. Attractiveness of turpentine, ethanol and a-pinene Expenment 1 compared the anractiveness of commercial _made turpentine and

ethanol, either alone or in combination (released from separare bottles). Attracriveness of

commercial grade ~rpent ine was compared with that of (t)-a-pinene in Experiment 2. Both

Experiments also contained an unbaited control.

Commercial grade mrpentine (MastercraftB Cat. No. 49-7 179-0) (Canadian Tire

Corporation Ltd., Toronto. Ontario) was determined bt. Cas chromatography/mass

spectrometry andyses to be composed of 73 % (k)-a-pinene. 2.6 Q P-pinene. 15 8 3-3-

carene, 1.8 % limonene and 1.3 % terpinolene. Ethanol (95 Q pure) was purchased from

Commercial Alcohols Inc. (Toronto, Ontario) and (k)-a-pinenc (98 % pure) was purchased

from Aidrich Chernical Co. (Milwaukee, Wisconsin, USA).

In Experiments 1 and 2. 15 ml of nirpentine, ethano1 or a-pinene was released from a

20-ml high-density polyethylene bottle (HDPE) (Cat. No. 66021-679, WWR Canlab.

Mississauga, Ontario) with a 4.8 mm hole drilled in the cenue of the polypropylene screw

cap. Release rates were determined gravimetrically at 24°C in a fume hood by weighing five

bottles of each compound daily for five days. The release rates of turpentine. ethanol and a-

pinene were Ca. 1 10. 732 and 22.5 rng/d. respectively.

Experiments 3 & 4. Cornparison of varying release rates of a-pinene Experiment 3 cornpared five release rates of a-pinene (30. 90 150. 300 and 450

mg/d), and Experiment 4 examined a-pinene released at 150. 300. 450. 600 and 750 rng/d.

Both experirnents also contained an unbaited control. These release rates were chosen based

on previous work by other authors demonsrrating attraction of Mo~iocltomus ro release rates

from 26-590 mgd. Expenments 3 and 4 used a-pinene lures purchased from Phero Tech Inc.

(Delta British Columbia). These lures consisted of &ml low-densiry polyethylene (LDPE)

bottles containing 9 5 8 of the (- i isomer and 5% of the (+) isomer. Each boule released 150

mglday (24°C) (Phero Tech Inc.) and multiples were used for the higher release rates.

Experiment 3 also used a ?-ml glas via1 Kat. No. 66020-936, VWR Canlab) with an open

cap (Cat. No. 66010-654. VWR Canlab). filled with a-pinene. which released Ca. 30 mgiday

(release rates detemined gra~imetrically as above). Three vials were used to achie\-e a

release rate of ca 90 mgd.

Traps For Experiments 1, 2 and 3, traps consisted of an open 1 1 -3-L Hunter Green (35 cm

long X 25 cm wide X 17 cm deep) plastic pan Cat. No. 2213, Rubbermaid Inc., Woosrer,

Ohio) placed on the ground. Each uap contained Ca. 3.5 1 of water to which 3 ml of

unscented Sunlight0 dish soap (Lever Pond's. Toronto. Ontario) was added to reduce the

surface tension of the water. Baits were suspended from a wire hung just below the top of the

pan, dong its length.

For Experiment 4. two 3 mm thick black polyvinyl chloride tPVC) plastic (Sintra@.

Alucobond Technologies Inc.. St. Louis. Missouri) cross vanes werr placed above the pan to

increase the trap catch of insects (Figure 2-1). The cross vanes (35 and 15 cm wide and 67

cm long) were slotted. placed at right angles to each other and trimmcd to fit inside the pan.

leaving 50 cm of vane exposed above the pan. Baits were hung in a 7.5 by 5 cm hole cur

3 . 5 cm from the top through the axis of the vanes. To prevent the traps from falling over.

each pan was secured with spikes placed in the ground.

Figure 2-1. Cross-vane traps used for collection of beetles, 5 Aug through 3 Sept, 1999, Lawlor Township, Ontario.

Layout of Traps Al1 expetiments were laid out in a complere randomized block design. Traps for

Experiments 1 and 2 were spaced 50 m apan and those for Experiments 3 and 4 were placed

25 m apart. Each treatment was replicated five times for Experiments 1 and 2 . and ten times

for Experirnents 3 and 4. Al1 captured insects and debns were removed from the uaps weekly

and traps were then supplemenred wirh fresn warer and boap. Iraps were rxated one gosition

each week within each replicate block to reduce trap position effecü. Captured Monochamus

beetles were identified to species and sexed by antennd length (Yanega, 1996). An

examination of the intemal geniialia of 30 M. scrrrellarirs and 10 iM. mritator beetles indicated

chat antennai len_@ correctly established gender.

Statistical Analysis For Experiments 1 and 2. trap catches of each sex were iransformed b?. loglo i x + 0.5)

to satisfy assumptions of nomaiity and homogeneity of variance (Zar. 1999). Transformed

data were analyzed by ANOVA by the General Linear Mode1 for randornized block designs

(~ i_ma~ta t@ version 2.03, SPSS Inc., Chicago IL. J followed b > the Tukey's test at P = 0.05.

A two-sample r-test was used to compare differencer between males and females within a

single treatment. For Experiments 3 and 4. trap catches for each sex for both M. scutellatus

and M. mutator Le Conte beetles were determined and the relarionship between reiease rate

and trap catch was anaiyzed by linear regression (sipastata). -4 two-sample t-test was used

to compare differences between males and females within a single treatrnent.

RESULTS AND DISCUSSION

Attractiveness of turpentine, ethanol and a-pinene In Experiment 1. traps baited with turpentine or turpentine plus erhanol caught

significantly more beetles than ethanol alone or unbaited controls (Fig. 3-?a). There was no

significant difference between attractiveness of mrpentine alone. and that of turpentine and

ethanol in combination. Ethanol alone was no more effective in attracting beeties than control

traps (Fi:. ?-?a). In Experiment 2. turpentine and (+)-a-pinene were equally effective,

capturinp significantly more beetles than unbaited controls (Fig. 2-lb). Although more

females were captured than males. the differences between sexes were not significant within

treatmenrs for rither experiment.

Erhanol alone had no attractise effecr for M. scurellatus. This supporrs findings of

Ikeda et al. (1980) for LM. altemarus. Chenier and Philogene (1989a) demonstrated a

synrrgistic effect between ethanol and ~rpent ine for M. scuteellarus. Similarly. Phillips et al.

(1988) and Fatzinger (1985) obsened synergism in attraction ro turpentine and ethanol for

M. carolinensis and M. tirillator. Ethanol release rates of 1.8-2.6 g/d (Chenier and Philogene.

1989a) and 23.6 g/d (Phillips et ai.. 1989) were considerably higher than 732 mg/d in the

present snidy. Ikeda et al. (1980) also demonstrated that significantly more M. altematus

were captured at traps baited with a-pinene and ethanol than with a-pinene alone at a-pinene

release rates of 400mgd and unknown ethanol release rates. The release rates of ethanol in

Exp. 1 may have been too low for detection by M. scuteliatus. This suggests thar there may

be a threshold concentration of ethanol in the air beIow which there is no detection or

subsequent response by M. scutellatus. Additional work is necessary to determine airborne

concentrations of ethanoi that are optimal for attraction of M. scutellarus and potential

spergism of ethanol and rnonoterpenes.

Females Males

Ethanol

Turpentine

Control

Fernales Males

Turpentine

a-Pinene

Control

Treatment 8 6 4 2 O 2 4 6 8

Total beetles captured (E - SE)

Figure 2-2. Response of d e and femaie M. scute~1afu.s beerles to traps baited with: A) ethanol plus nupentine, ethanol, nupentine. and blank control traps; and B) turpentine. a-pinene, and blank control mps. 22 Jun through 25 .4ug, 1998, Wells Township, Ontario. Bars with the same letter are not significantly dserent at P=0.05 (ANOVA with Tukey's test). There were no significant differences (P >0.05) in number of males and fernales caught for any of the above treatments.

Turpentine. and irs major constituent a-pinene. appear to be equally attractive to M.

scr~tellatus at the release rates used in the present snidy. Chenier and Philogene (1989a)

determined that (3-a-pinene was more attractive than a monoterpene biend similar ro

turpenune for M. scurellatus at release rates of O.j9g/d and 1.36g/d. respective1 y. Turpentine

was determined to have an attractive effecc for M. caroline~rsis and M+ tirillaror when

reieased at a rate of 1.7o/d (Phillips et al.. 1988): and Fauinger (1985) determined that (Sa-

pinene was attractive for these species at 36-61 mgd. Billings (1985) determined that

turpentine alone a a s no more attractive than unbaited conaol traps for M. tirillafor.

Moeck (1970) derermined maximum a-pinene concentrations in the field to be ca.

240 mdd. Stromvall and Petersen (1991) determined that the air above freshly cut pine

branches contained monoterpene concentrations of 1000pg/m3. which decreased to 500ug./rn3

in pine cut a few days earlier. Four weeks afier thinning in July. monoterpene levels in a

related spnice stand were oniy 10% that of original levels (Ikeda et ai.. 1980). Ikeda er al.

(1980) demonsuared that pine logs left in the field become unattractive to M alreman<s

within three weeks. This couid be because monoterpene release by the plant varies

seasonaily, but aiso decreases exponentially following death.

Attraction to varying release rates of a-pinene Very few beetles were captured in Experiment 3. therefore rhe data were not

analyzed further. in Experirnent 4. the highest numbers of beetles were collected at baits

releasing 150 mg/d of a-pinene. There was a significant positive relationship between release

rates of a-pinene and trap catch for fernale but not for male M. sciirellarzrs (Figs. 1-3. 2 4 .

Catches of female M. mutator did not increase with increased release rates of a-pinene (Fig.

1-45) but those of males did (Fig. 2-6). More females were caughr than males in both species.

but the differences between sexes were not significant for any of the trearments.

More beetles were collected al higher levels of a-pinene. those above 45Omg/d for dl

oroups. M. scurellarus was attracted to baited traps releasing a-pinene ar 590mg/d (Chenier C

and Philogene, 1989a). and Ikeda et al. (1980) demonstrated M. altenzatiis attraction to

release rates of 400mdd. M. ritillator was attracted to a-pinene release rares of 3600mgd

(Billings. 1985). while M. carolinensis and M. ritiZI~rur were anracted to release rates of 26-

61rng/d (Fatzinger, 1985). This suggests that the genus is able so detecr and respond tu a wide

range of volatile release rates. There were large numbers of beetles collected at unbaited

control traps in the present study, suggesting that some other factor, such as trap silhouette.

may have been involved in attraction.

Release rate ( m g i d )

Figure 2-3. Relationship between release rates of a-pinene and rrap catch of femaie M. scurellatw adults, 5 Aug through 3 Sept, 1999, Lawlor Township, Ontario. Slope of regression line is significantly different from zero (N=60 traps. r-=O. 1 IO. P=0.0 10).

R e l e a s e rate (rn g/d)

figure 24. Relationship between release rates of a-pinene and uap catch of male M. scurellams adults, 5 Aug through 3 Sept. 1999, Lawlor Township, Ontario. SIope of regression line is not significantly different h m zero (N= 60 traps. r2=0.0409, P4.12 1).

R e l e a s e rate ( m g l d )

Figure 2-5. Relationship brtween releüse rares of a-pinene and trap catch of female M. mriraror ndulrs. 5 . h g through 3 Sept. 1999. Lawlor Township. Ontario. Slope of regression line is no[ significantly different from zero W=60 tnps. r:=0.030 1. P=O. 185).

Release rate (mgfd)

Figure 2-6. Relationship between release rates of a-pinene and trap catch of male M. mututor adults, 5 Aug through 3 Sept, 1999, Lawlor Township, Ontario. Slope of regression Iine is sipificandy different h m zero (N=60 traps, ?=0.0752. Pr0.034).

There was a positive relationship between a-pinene r e l e ~ e rate and trap catch for

female M. scutellatris and male M. nzurntor. The reason why there was no such relationship

for male M. scutelZatcts and female M. niiitator is unclear. If attraction to a-pinene were a

hinction of beetle gender. it would be expected that there would be significant positive

relationships between release rate and trap catch for fernales or males of one or both species.

Alihough positive results were seen in the present study. they were relatively weak for both

female M. scutellatus and male M. mutator. This may have been a function of marginal

response to low release rates. as a 3ûûmg/d a-pinene release rate approximates that from

only 30kg of bait iogs in the field (Ikeda et al.. 1980). Further examination of a wider range

of a-pinene release rates is necessary to better understand host volatile attraction in both

species.

CONCLUSION Results from this study indicate that Mo>lochamccs beetles are able to detecr a range of

a-pinene release rates. This study was unable to demonstrate attraction to ethanol. or

synergism between ethano1 and either turpentine or a-pinene, at the release rares examined

There was little or no difierence in attraction to release rates under 3ûûmg/d. and die majonty

of beetles were anracced to traps releasing greater than 3ûûmg/d. This supports previous

research into vono oc han rus species. which demonstrated increasing attraction to higher levels

of a-pinene. 50 upper level of attraction has been demonstrated in Monoclta~nus.

Examination of a broad range of release rates would give a clear picnire of attracrion ro dead

and dying trees in the boreal forest.

Previous authors used one release rate of a-pinene and all snidies have demonstrated

attraction to Monochamus. Further work could increase the release rates of a-pinene. and use

a broad ranse to determine upper limits for attraction. Examination of increasingly higher

release rates would give an indication of the upper Iimit for attraction to M. scurellarr<s and

M. mutator. It may also derermine if sex-based differences in attraction are dernonsuared by

these species. Further work could also attempt to measure a-pinene release rates above log

piles after cutting. to determine levels in a field situation. A number of trap desips could

also be examined. to determine if trap silhouette combines with a-pinene release to enhance

attraction in species of Monochamus.

Chapter Three: Influence of inter-specific competition and niche partitioning on oviposition by Monochamus scutellafus Say (Coieoptera: Ceram bycidae)

INTRODUCTION

LCfunochumus ~ ~ ~ i ~ ' 1 l ü i i i ~ (Say), the white-spottec! m i n a y ..+ s ~ q e r hee:!~, is found

throuohout - North Arnerica, with the exception of the central United States (Yanega. 1996).

After emerging from dead pine lots. adults undergo a penod of maturation feeding on young

pine twips and foliage (Wilson. 1962a). After mating, females oviposit in scars excavated in

the bark of dead and dying pine species. Larvae emerpe and feed in the phloem layer until the

third l a n d instar. in which they tunnel into the sapwood and later heartwood. where they c m

feed for up to two years (Rose. 1957). Larval feeding reduces structural qualities of the wood

and facilitates entrance of other insects and fungal pathogens. contributing to wood

decomposi tion in the forest ecosystem (Pmelee. 194 1 ; Gardiner. 1957; Wilson. 1962a).

.A number of insect families utilize wood for feeding. and sires for rnating and

oviposition. Many are capable of attacking living trees, but the majority of these insects are

dendrophagous, using dead and dying wood. The community structure within dead wood

changes from the initial colonizen. such as bark beetles of the family Scolytidae. feeding on

fresh dead phloem, to secondary attack by boren such as the family Cerarnbyidae. A variety

of species amive at the resource throughout the earlier stages of decomposition. and

community composition changes wi th tirne (Thomas, 1955; Zhong and Schowalter, 1989).

Primary insects arrive first, and mosr cornpiete oviposition and 1an.d development before the

arriva1 of secondmy species. M. scutellnrus is a secondary insect. generally incapable of

killing the host, and reliant upon some other agent to attack and kill the healthy uee, such as

the scolytid bark beetle Ips pini (Say) (Gardiner, 1917). These jpecies may not kill the tree

directly, but may hasten death, or introduce pathogens that decrease vigour and euentually

kill the tree.

A guild is defined as a group of species sharing the samc habitat. and having similar

resource requirements and foraging strategies (Flamrn et al.. 1987). M. sncrellarrts is a

phloem and sapwood borer. part of a guild with obligate phloem-feeding larvae. .4n average

phloem surface area of 3 1.75 cm2 was required for foraginp by M. titillator (Fabncius)

(Coulson et al.. l976), a beetle of similar size to M. sciirellatur 1 Yanega, 1 996). and assurned

similar nutritionai requirements. These larvae reach up to 3.5 cm in length in the founh instar

(Wilson, 1962a). and therefore have greater nutritional requirements than smaller species

sharing the resource. After the second instar. as the amount of pnloem is geatly reduced. M.

sciirellarus lantae can tunnel up to 7.5 cm into the heartwooc (Gardiner. 1957). retuming

periodically to the phloem to feed. The smaller bark beetle species require less surface area

for larval feeding; however. these are prolific breeden. widi much higher population

numben exploiting the phloem resource (Coulson et al.. 1976'1. Resource use may result in

intra-specific cornpetition between members of the same species, or inter-specific

competition with other insect species sharing the resource. Competition could be intense if

both groups were to feed in the same area at the same time. The sequence of sub-cortical

insects miving at a host and the influence of competition on insect species feeding widiin

fallen logs has been examined by previous authors (Yoshikawa, 1987a, b; Stephen and

Dahlsten, 1976; Flamm et al., 1989; Post and Werner. 1988: R a n h and Borden. 199 1:

Poland and Borden, 1994: and MiIIer, 1985, 1986).

Competition between species in this two-dimensional feeding arena rnay be: 1)

interference or direct competition through ccannibalism or predation; or 2) exploitative

through exclusion by utilizing the resource before amval of the second species (Byers.

1989). Most members of the phloem-feeding guild are able to successfully avoid this

competition through resource partitioning by spatial or temporal segreption of feeding and

oviposition sites. Spatial segregation has been demonstrated in Ips calligraplzi~s Germ.. with

hiphest numbers found in areas where insect associates had been mechanically removed or

excluded (Miller, l984a,b, in Miller. 1986). Yoshikawa (, 198723) determined that

Monochamiis altematus Hope larvae were not affected by other species under the bark.

because larvae were successful in either inter-specific competition or niche segregation.

The influence of competitive interactions between LM. tztillator. Dendrocrorziis

frontalis Zimmermann and 2's calligrapliiis (Germ.) has been documented by various authon

(Coulson et al.. 1976: Flamrn et al., 1989: Miller. 1985, 1986). However. there has been no

examination of competition between M. scutellatus and other species within the phloem-

feeding guild. The purpose of this study was to examine the factors influencing success of

M. scutellatus larvae under the bark of dead pine. The objective of the study was ro

determine if different members of the phloem-feeding guild were present in the sarne area at

the same time in the season, and if so. CO examine the extent of temporal andior spatial

segregation between M. scutellatus and other insect species. Competition may also be

influenced by host species characteristics. Red and white pine logs of similar diameter were

used in this study to examine the influence of host tree species upon @Id suucture and

competitive interactions of M. sctctellatus. Other factors, such the predator and parasiioid

complex, and Sun exposure of logs, were also exarnined, to determine an' potential effect on

population dynamics of M. scutellatus.


Experiment 1 Twelve red pine i Pinus rrsinosa Ait.) and [en white pine (Pinus strobus L.) log. each

2 m in lene@ and averaginz 18.5 2 1.9 cm in diameter. were cut in late May 1998. and

p!xctd at a site in Wellc h w n s h i p . ca. 30 km N of Thessalon. Ontario (46' 15' N. 83' 22' E).

Logs were placed in a semi-shaded thinned pine stand. in a &grid formation with 5 m spacing

between each log. Red and white pine logs were used to detemine if oviposition and survival

varieci between host species. Logs were altemated. red pine and white pine. throughout the

3ïd. - One half of each log ( 1 m ) was covered with 0.625 cm galvanized hardware cloth.

and the other half was l t f t open. This was done to exclude the larger M. sciitellatus beetles

from the log surface. in order to examine potential differencec in guild dynamics between

two adjacent areas. one with M. scutellutus. and one without. Two logs of each species were

removed randomiy at tuo-week intervals throughout the stud! period, June through August.

and were taken to the laboratory. The hardware cloth was removed and each log was cur in

half, at the screenho screen interface. with each half kept separately in screened cages in the

laboratory. Al1 Scolytidae emerging from logs were collecred until the end of die study

period, in Iate August. The number of M. scutellatus oviposition scm on the surface of the

logs was counted and the bark was removed from each log later in the fall of 1998. Al1

Monochamus beetles reared through in the process of this and subsequent experiments were

identified as M. scutellanu (Yanega, 1996).

The number of oviposition plugs was also determincd In Chapter 4, it was observed

that 96% of scan containing a brown sticky substance (the 'plug') contained an egg upon

dissection. This approximately 1:l ratio allowed the assumption that each plug would

represent a scar containing an egg. These plugs were clearly visible under 4X magnification,

and were used a s an indication of the presence of eggs in excavated scars.

The number of M. scutellatus feeding gaiieries and entrance holes into the sapwood

were counted for cornparison of Iarval success between red and white pine logs. The surface

area required by M. scutellntus for larval feeding has not been established in the literature.

The total surface m a of each gdiary was rneajured using a do: grid niettiod. 'This involved

using a 20 X 20 cm grid. with the dimensions of each centimeter marked in a block with a

dot in the centre. This grid was randomly placed on a log, and the number of dots within the

dimensions of each gallery was noted. to give an indication of the number of square

centimeten within the gallery. The accuracy of the grid method was tested on a sub-sample

of ren feeding galleries using a planimeter to mesure actual dimensions afrer measurernent

with the grid. It was determined that the method was accunte within an average of 1.7 10.3

M. scutellarw femafes were able to p t under the mesh and oviposit in the bark of

both red and white pine logs, making it impossible to examine differences between areas

with and without M. scurellatus. Therefore. only uncaged data were used for analysis in dus

smdy. because this area most closely resembled a natural situation. Two-sample t-tests were

used to examine differences between uncaged red and white pine logs in number of scws

excavated, oviposition plugs, enance holes into the sapwood, and surface area of feeding

gaileries for LW. scutellatus. Two-sarnple t-tests were also used to examine the number of Ips

pini adults emerging from red and white pine Iogs caged in the lab (SibmaStat@. version

2.03. SPSS Inc.. Chicago. IL).

Experiment 2 Nine red pine (P. resinosa) and ten white pine (P. strobus) logs (each 1 m in len-gh

and averaging 17.4 + 2.6 cm in diameter) were cut in Iate May 1998 at the Wells Township

site. These 100s were placed in a grassy area near a logging road in a red pine plantation in

Kirkwood Township, ca 20 km nonh of Thessaion, Ontario (46" 20' N, 83" 33' E). The

purpose of this snidy was to examine spatial distribubon of M. scuteliarus and orher mem*oers

of the phloem-feeding guild around the circumference of the log. Logs were placed in a grid.

with 5 m spacing between each log. Logs were restricted by species to one side of the grid,

with ail red pine on one side. and al1 white pine on the other.

The circumference of each log was divided into zones. based on the face of a dock

(Fig. 3-1). with the middle of zone 1 1-1 representing the top of the log. and the middle of

zone 5-7 representing the bottom of the log.

zone 71-1

Figure 3-1: Dia_gnmmatic representation of the cross-sectional division of the circumference of snidy logs into 6 equd zones.

Two logs of each species were rernoved randomiy at 2-week intervals between June

and August 1998, and were taken to the laboratory. The number of M. scutellatza oviposition

scars in the bark of each log was counted, and dl bark was removed from the logs. During

bark removal, a significant number of pupd cells of the northem pine weevil, Pissodes

nemoremis (=upproximatus) Germ.. were observed so these were included. as well as any

other insects observed under the baric,

AI1 data were transformed using logio (x + 0.5) to satisS assumptions of normality

and homogeneity of variance (Zar, 1999), and ail subsequent analyses were performed on

transformed data. Two sample t-tests were used to exmine differences between pine species

for the mean number of M. scutelLanis scars and P. nemoremis pupal cells. One-way

ANOVh, followed by the Tukey's tesr, were used to compare die number of scvs and pupd

cells per log zone for red and white pine (SigrnaStatO).

Experiment 3 Based on 1998 results indicating that some spatial segregation had occurred (refer to

Experiment 2), it was hypothesked that sun and shade and log placement on the ground

could influence site selection. Experiment 3 was conducted in 1999 to examine these factors.

Twelve white pine (P. strobu) logs were cut at the Kirkwood Township site and placed at

the Wells Township site in early June. These logs were 1 m in length. averaged 19.1 f 1.3 cm

in diameter, and were placed in a grid with 5 m spacing between each log. Six of the logs

were placed in full Sun. and six were placed in a semi-shaded. diinned pine stand, in order to

examine the influence of sun and shade conditions on oviposition sire selection. Al1 logs

were raised ca 10 cm above the ground by nailing two 5 X 10 X 10 cm blocks on each end

of the log. This was done in order to expose the entire circurnference of the log. The 12 logs

were left at the site throughout the field season. Each log was examined weekly, and al1 new

M. scutellatw oviposition scars and P. nemoremis oviposiUon holes were counted in order to

examine the oviposition perïods for both species.

Two-sarnple t-tests were used to examine differences between logs in sun and shade

conditions for number of oviposition scars and oviposition holes (SigmaStatGD). The number

of oviposition scars and holes was dso coliected to determine the temporal oviposition

pattern for M. scurella~rs and P. neniorensis in the field.

RESULTS

Experiment 1 M. scutellatzis females were able to get under the screening to oviposit on both red

and white pine logs, so oaly uncaged Iogs were used for andysis. There were significantly

more LM. scutellatzis oviposition scars excavated on white pine than red pine (Table 3-1). The

number of oviposition plugs deposited was deterrnined to be indicative of the number of

scars containing eggs. There were significantly more plugs deposited on white pine,

compared to red pine (Table 3-1). On red pine, 73.5 % of scars contained an egg, while on

white pine, 8 1.3 % of scm contained an egg, but the difference was not si,gnificant.

The mean number of larval entrance holes into the sapwood was also significantly

orearer for white pine than for red pine (Table 3-1), as it is a function of the number of eggs C

deposited. Examination of the ratio of enuance holes to eggs c m indicate larvai survival to

diird instar, where they begin to tunnel inro die sapwood. In white pine, 42.1 8 of cggs

reached the third instar. wherev in red pine, only 27.9 % of eggs reached this stage. The

average surface area connimed by larvae was also significandy greater on white pine logs.

37.2 cm', compared to 31.9 cm'on red pine (Tabie 3-1).

The majority of ernerging scolytid beetles were Ips pini. so this was the only species

examined for cornpetition studies in 1998. Peak emergence for this species occumd from

mid- to late-lune on red pine, and in early July for white pine (Fi~g. 3-2). The number of 1.

pini adulü ernerging from logs in the lab was significantiy p a t e r for red pine than white

pine (Fig. 3-3). Logs were taken to the lab and insects were rernoved from caged logs

immediately following emergence, preventing reentry and oviposition by offspring. Al1

offspring were thus the fust genention of beetles seen in the field (Thomas, 196 1).

Table 3-1. Mean number of M. scutellatza oviposition scan, scars containing oviposition plugs, entrance hoies into the sapwood and gaIIery surface area for uncaged red and white pine logs in exclusion cage studies, 1998, Wells Township, Ontario.

Pine species Red White

Oviposition scars 36.9 4 7.9" 78.0 t 16.0' Oviposibon plugs 27.2 k 5.4" 63.4 I 12 .5~ Entrance holes into the sapwood 7.6 h 6.0" 26.7 2 17.1b Gallery surface area (cm2) 24.9 t 2.7" 37.2 f 4.gb ' Row means followed by the sarne letter are not si,W~cantly different at P = 0.05 (NO- sarnple t-test).

- - O . - W h i t e pine

Log collection date

Figure 3-2. Number of Ips pini adults coilected in cages in the lab from uncaged red and white pine logs collected 9 Iune through 18 Aug, 1998 fiom field sites in Wells Township. Ontario.

R e d pine . .O- - White pine

8 eetle collection date

Figure 3-3. Cumulative cmergence in cages in the [ab, 25 June rhrough 14 Aug, 1998. of adult Ips pini from uncaged red and white pine logs from field sites in Wells Township, Ontario. There was a significant difference berneen tords of Ips emerging fiom red and white pine logs at P = 0.05 ( ~ o - sample t-test).

Experiment 2 The majority of oviposition s c m were excavated by M. scutellatus on the sides of red

pine logs, in zones 1-3. 3-5. and 9-1 1; however, the differences were not significuit (Table 3-

1). The number of scars was lowest on the top of red pine logs, in zone 11-1, and the bonom.

in zone 5-7 (Table 3-21. In white pine, oviposition was similar in al1 zones. regardless of

location on the log surface (Table 3-2), and none of the differences were significant. Between

red and white pine. the differences between mean number of scars excavated in each zone

were not signifianuit ar P = 0.05 (Table 3-2). There were significantly more P. nernorensis

pupai cells in zones 5-7 and 7-9 than the top of the log, zones 9- 1 1 and 1 1-1, for white pine.

The number of P. nernorensts pupal cells on red pine was not exarnined because ail cells

observed were found on only one sample log.

Table 3-2. Xumber of M. scutellatus oviposition scars and P. nemoremis pupal ceils found in zones around the circumference of red and white pine logs placed on the ground 16 Jun through 11 hug 1998, Kirkwood Township, Ontario. The circurnference of the logs was divided into equal zones based on a dock face mg. 3- 1 a).

Log zone No. M. scutellatus scars No. P. nemoremis pupal cells (mean k SE) (mean + SE)

Red pine White pine White pine'

' ;Me= within 3 colurnn followed by the same lener are not significmtly different at P = 0.05 ( M O V A wich Tukey's test). ' Dais h m white pine is presented becaux only one red pine log wm infested. and dam were not used in the analysis.

To hinher examine differences in oviposition and lavai success berween the top and

bottom regions of the Iogs. data from zones 9- 1 1 , 1 1-1, and 1-3 were cornbined into the 'top'

region. and data from zones 3-5. 5-7. and 7-9 were combined into the 'boaom' region. There

were no significant differences in number of M. scutellatur scars excavated on top and

bonom of red pine 10gs (P = 0.481). or of white pine logs (P = 0.470). There were

significantly more P. nemoremir pupal cells on the bonom of white pine logs (P = 0.020).

Experiment 3 There were significantly more scan excavated by M. scutellatus on logs when placed

in full su, compared to logs placed in a shaded ana (Fig. 3-4). There was no significant

difference in number of P. nemorensis oviposition holes on logs for shaded or sunny

conditions (Fig. 3-5).

For ,M. sc;lteilub~. oviposition Segm in lm June and continued until the end of

August, with peak oviposition extending fiom mid- to Me-July (Fig. 3-6). For P. nemorensis.

oviposition also began in late June, and continued until early August, with a peak in mid- to

late-July (Fig. 3-7).

Figure 3-4. Cumulative number (BE) of M. scureilasus oviposition scars on white pine Iogs in sun and shade conditions. examined 29 lm through 3 t h g , 1999. Wells Township, Ontario. There was a significant difference b e m n cumulative totals under m and shade a? P = 0.05 (two-sample r-test).

Figure 3-5. Cumulative number (SE) of P. nemoremis oviposition holes on white pine logs in sun and shade conditions. exa-ed 29 Jun through 3 1 Aug, 1999. Wells Township. Ontario. There was no si-piiïcant ciifference beoucen cumulative tords under Sun and shade at P = 0.05 (NO-sarnple t- test).

Figure 3-6. Number of new M. scu~eLIanc~ oviposition scm excavated on white pine 10~s. 19 Jun through 31 Aug, 1999. at field sites in Wells Township. Ontario.

Figure 3-7. Number of new P. nemoremis oviposition holes on white pine logs. 29 Jun thmugh 3 1 Aug, 1999. at field sites in Wells Township. Ontario.

Temporal Segregation of Oviposition The oviposition penod for M. scutellutus extends from June through August. with a

peak seen in mid- to late-July. This supports Rose (1957). who documented hat 90% of LM.

scutelZafus eggs were laid in a four to six week period in June and July. Adult M. scurellatzu

emergence begins in Juae in the b o r d forest, and adults undergo a period of maniraiion

feeding for 7-10 days before searching for mating and oviposition sites (Rose, 1957). There

is a sharp decline in oviposition in early August. This is consistent with the life history of M.

scutellaw in this region, as eggs laid in August would stiIl be in the second instar in the

phioem layer when temperanues dropped in October, and would no? be able to enter the

sapwood to over-winter. renilting in mortdity.

For P. nemorensk the oviposition period extends frorn June through August. with a

peak from mid- to late-Juiy in the b o r d forest. These results support the conclusions of

Phillips et al. (1987) for an oviposition peak occumng in early surnmer. Adults that have

over-wintered in the duff or under the bark emerge in May and feed for approximately three

weeks before the start of the oviposition penod (Finnegan, 1958). P. nemorensis has four

larval instars, before pupating under die bark. Oviposition by females later than early August

would also result in offspring in fourth instar or in pupal cells under the bark when

temperatures dropped in October, resulting in mortdity.

The fmt Ips pini ûdults emerged in late June, suggesting that oviposition occurred in

May, as this species has a 4-week development period (Thomas, 1961). This supports

Thomas (1961), who determined that the fint emergence of I. pini adults in the boreal forest

occurred in early May, with attack and oviposition in late May. 1. pini has two generations

per year, the fint with 2-3 broods. and the second with one brood (Thomas, 1961). This also

supports findings that scolyùd numbers were usually on the decline when cermbycid Iarvae

were noted at logs (Howden and Vogt, 195 1). Peak emergence for the fmt brood of 1. pini

occun just before peak oviposition for M. scutellatus and P. nemorensis. There was no

second-generation emergence observed in this study, because logs were removed h m the

field and caged in the lab to observe emergence, and al1 adult beetles were removed before

oviposition could take place.

Temporal segregation (e.g., ovipositing early in the season and having a short

development penod) allowed I. pini to effectively avoid cornpetition, as Monochmus larvae

cui ingest any eggs or Iwae they encounter under bark (Hamm et al., 1989). The earlier

development of Ips ailowed them to get a head start on the Iarger larvae. and leave the area

before foraging began. Miller (1985. 1986) and CouIson et al. (1976) suggested that

Monochamus was an important mondity factor, resulting in reduced Ips emergence.

Schroeder (1997) suggested that the timing of cermbycid oviposition, in relation to the

developmental stage of bark beetles sharing the same habitat, might have an effect on

cornpetition and subsequent survivai of larvae of both species. By temporally segregating

oviposiùon and emergence. I. pini females were able to survive in a habitat where the larger

cermbycid larvae would otherwise have a cornpetitive advantage and greatly reduce

population numben.

Spatial Segregation of Oviposition Sites The number of M. scutellanrs oviposition scars was lowest, and the number of P.

nemoremis oviposition holes was greatesi, on the bottorn of logs resting on the ground. This

result for LM. scutellatus supports those of Rose (1957) and Raske (1975), that beedes do not

use the bottom region of log flat on the ground. Some factor related tu proxirnity to the

ground prevented oviposition on the boaom of logs, because when logs were raised, femaies

preferentially oviposited in the bottom region. When raised, the fernaies had free access to

the bottom of the log, and the influence of vegetation may not have been as great. This

supports conclusions of Raske (1975) that beetles were most likely to oviposit on the lower

regions of decked spruce logs.

The smdler P. nemoremis may have been able to exploit areas of the log where M.

scuteiiuzus wzrr not found, because the larger ceraïbycids were not *le te fiilly zcess rhir

area, due to proximity to the ground, shade, and surrounding vegetation. Shroeder (1997)

suggested that bark beetle species that share the same log generally breed in different areas.

and can thus avoid niche overlap; however. in the absence of cornpetiton these beetles are

able to fully exploit the new area When M. scutellatu was excluded from an area by

constriction, P. nernorensis numbers increased because larvae were more likely to survive to

the pupal stage without encoumering the larger cenmbyid larvae.

Femaie M. scurellanïs perhaps were not able to oviposit on the bonorn of the logs. or

the number of larvae foraging in the phloem rnay have been reduced due to other factors.

Upon peeling the bark from study logs. M. scr~retelhu feeding galleries were evident in most

regions of the log, and no other insects were detected in these areas. Cornpetitive release was

seen, as P. nemorensis numben were greatest in areas where M. scutellatus numbers were

most Limited. P. nemorensis survival to the pupal stage wwas greatest here, suggesring that M.

scutellatus larvae had a derrimental effect on survivai of P. nemorensis under the bark,

Effect of Sun Exposure on Site Seledon For M. scutellatus, there were significantiy more scan excavated when 10,s were

placed in sunny conditions. M. scutellatus -des have been observed to mate in full

sunlight, but oviposit in the shade (Rose, 1957; Raske, 1975; Chapter 4). It may be that

femaies rnated in full sun. then remained at the same site for oviposition. The degree of Sun

zxposure may have iaried over &e su r f xe of t'ie !op, and females rnay have chosen shadier

places for oviposition. The reduction in sun exposure in shaded areas may have prevented

mating, and subsequent oviposition. There was no significant difference in numbers of P.

nemorensis holes excavated on logs in sun or shade, suggestinp that P. nemorensis females

are unaffectecl by sun exposure. Phillips and Lanier (1983). concluded that shaded field

conditions are preferential for oviposition by P. nemorensis. Potentially higher temperatures

in sunny areas did not deter oviposition. as females utilized both sites in the same manner.

Host Tree Species Significantly more I. pini emerged from red pine than white pine, suggesting thar

oviposition and larval success were greater on red pine. The greatest numbers of @s were

collected at logs removed from the field eady in the season. before oviposition by M.

scutelIum, and thus before larval foragiag by the larger cerambycid. It is unknown if

oviposition was higher on red or white pine, but increased numbers woliid suggest it was

higher on red pine. This may be indicative of spatial segreegation. as Ips choice of a species

not oviposited upon as heîvily by other guild members rnay have reduced the potential for

interactions under the bark.

The greatest nurnben of P. nemorensis pupal cells were found on white pine in 1998.

suggesting that Iarvae were more successful on white pine logs. and many more individu&

reached the pupai stage than on red pine. Phillips and Lanier (1983) stated rhat red pine is the

prefemd species for oviposition for P. nemorensis.

on red or white pine, and therefore impossible

It is unknown if oviposition was higher

to support or refite this conclusion.

Interactions with M. scutellatw or other larger insects in the phloem-feeding guild also were

not examined in that study, so it is not possible to determine if cornpetition had any role in

this discrepanc y.

M. scunlIU~"as oviposidon scm were fouad ir! cignificantly preater numben on white

pine compared to red pine. It was observed in the present snidy that white pine logs generaily

had a thinner bark then red pine logs. Bark thickness does play an important role in

oviposition site seleccion in M. sutor (Zhang et al., 1993) and M. altematus (Nakamura et al.,

199%). with an increase in oviposition on logs with a thinner bark. Results here support

those of Nakamura et al. (199%) for LM. aitemoncs - even in logs where she had excavated

scm, fernales were more Iikely to oviposit on 100s with a thinner bark. A fernale may reduce

the arnount of time invested in excavation by choosing a thinner bark. in behavioural studies

conducted in Chaprer 4, it was observed that a female invested a shoner amount of tirne

excavating on white pine, perhaps because she did not have to dig as deeply inro the outer

bark to reach the phloem Iayer to deposit an egg. A fernale ovipositing on thinner bark

reduces the invesanent in a single oviposition event, and inc~ases her fitness by improving

her efficiency over time, which may explain the increase in oviposition and larval success on

white pine.

The rnean number of third instar entrance holes into the sapwood w u significantly

greater for white pine than red pine. L m a I survival to third instar w u also greeater on white

pine, dthough stiil l e s than 45 9%. These results would sugpst that there is 3 hi& level of

monality pior to the third larval instar in this species. supporthg previous concIusions that

M. scutellatus mortaiity under the bark is quite h i a . 70 % on balsam fir (Rose. 1957), and

71 % on white spruce (Cerezke, 1977). It is unknown why larval survival was greater on

white pine than on red pine. This may be due to a number of factors outside the scope of the

present study, such as temperature. phhem characteristics. and moisnire levels.

The surface area consumed by M. scutelIntur larvae was also significantly greater on

white pine Iogs. The diameter of white pine (17.0 f 0.8 cm) was sixniiar to that for red pine

(17.8 f 0.8 cm), Îndicating that rhe amount of surface area avaiiable for iarval braging ivûs

similar as weU. Results here are similar to those reported by Coulson et al. (1976), of 3 1.75

cm' for M. titillator feeding galleries on loblolly pine (Pinus taedu L.). Anbutsu and Togashi

(1997b) found that M. altematus larvae consumed an average of 107 cm' from hatching to

formation of the pupal chamber in P. demiflora Sieb. et Zucc.. Larvae were able to utilize a

greater surface area on white pine. but the depth of these galleries is not known. Larvae will

periodicaüy r e m to fked on phloem. as they generalIy do not feed on the less nutntious

sapwood or h e a r t w d unless phloem resources are depleted (Hanks, 1999). It may be dia1

larvae have to tunnel deeper into red pine phloem, and the surface area would be reduced.

whiie the same mass of phloem would be consumed.

Al1 of these factors suggest that M. scutellatu and P. nemotensis are more successful

on white pine than red pine. and I. pini is more successful on red pine, although it is

unknown if oviposition was actually greater on one host tree species compared to the other.

or if success was influenced by other factors.

Mortality Factors There were no predaton or parasitoids obsewed emerging from logs caged in the lab,

therefore it was determined that these have l inle influence on population dynamics of M.

scutellaîw, as found by Pannelee (1941) and Rose (1957). Reduced M. scurellatus survival

observed during this study must have been due to other factors, such as a reduction in quality

and quantity of phloem, or an increase in crowding, competition or cannibalism. Poor

conditions resulting from crowding, such as decreased food availability. tesult in adults that

are smder, with reduced fecundity (Leather. 1995). In less crowded conditions, l w a e have

greater access to food resources, and thus improve their own chances for survivd and future

reproductive success.

Larval cannibaiism may have been a factor in reduced survival of early instars. as

Monochomu larvae will consume larvae, eggs and pupae of its own and different species

(Rose. 1957). Rose (1957) documented that when M. scutellarus larvai density was high.

particuldy in earlier instars. cuinibdism resulted in considenble mortality. Anbutsu and

Togashi (1997b) also determined that conspecific bites resulted in considerable mortaiity in

M. altemam. Victonson and Wikan (1996) suggested that M. sutor L. larvae used sound

production in temtorial defense, signaling their presence to other larvae to avoid competition

and cannibalism under the bark, Saiiba (1972. in Victorsson and Wikars, 1996) showed that

M. sutor larvae were able to Nm sharply in feedinp galleries to avoid other Iarvae in close

proximity. A sirnilar pattern was observed in the present study: gdleries ofren missed

intersecting with other gdleries by millimeten, and larvae produced a loud chirping sound

when under the bark.

CONCLUSION

Subcortical tissues of dead and dying trees represent a high quaiity food source, but

one which is in short supply and degrades very quickly after death (Hanks, 1999). The

ephemeral nature of the resource results in extreme competition during larval feeding, often

resulting in mortality due to cannibaiisrn and reduced resource quality and availability.

Larger species are able to out-compte smaller and weaker species under the bark, and

exploit available resources (Müler, 1985), and those species that share the resource must

have adaptations to avoid larger larvae. It is unknown if avoidance is detennined by acoustic

or olfactory means, as Monochamus larvae are capable of sound production (Victorsson and

Wickars, 1996). and bark beetles cm use pheromones fiom other species to determine the

extent of competition (Byen. 1989).

Niche partitionhg through spatial a d o r temporal segregation, allows insect species

in the phloem-feeding guild to avoid competition, improve fitness. and maintain their place

in the guild. Evasion behavioun such as timing of b r w d development, and segregation to

portions of the log inaccessible to M. seutellarus. allowed the smaller 1. pini and P.

nemoremis to remain in the guild and share resources with the larger cerambycid. This

system exists in a similx fashion to that of M. titillatort I. caUigruphur, and D. frontdis

described by Flamm et al. (1989). Direct contact with the larger indiscriminate fonger is

avoided through these strategies, encouraging co-existence arnonpt guild memben.

Some degree of spatial segregation was seen in I. pini, which oviposited more

frequently in red pine over white pine. However. this segregation was not complete, as somç

females chose white pine as well. Ips was dso temporally segrepated, with two generations

per year. Earlier oviposition by over-wintering fernales dlowed for adult emergence fiom

logs before the arriva1 of larger guild membea. There was no evidence of spatial or temporal

segregation between M. scutellatur and P. nemorensis. There was no demonstrated effect of

the smaller Pksodes, as Monochamus larvae are cannibalistic, and probably feed upon

Pissodes eggs, larvae and pupae encountered under the bark. This supports results of

Yoshikawa (1987a) for the related M. altematus, which is also unaffected by other insect

species under the bark.

Furthzr study is required to better undestand niche dynamics md avoidance

cornpetition under the bark of coniferous species. This study has determined that odier insect

species have no effect on Monochu.s. but M e r study is needed into the impact of

Monochamus upon other guild memben. h the populations snidied, predators and

parasiroids did not have a measurable effect. Further work is needed to examine influences

on population dynamics outside the guild. This could eventuaily be used in biocontrol

pro-gms for reduction of Monochamui populations where required.

This work has provided a beaer understanding of the timing of oviposition by M.

sciitellizrur. To reduce economic loss at field sites and mil1 yards. logs should be removed

from the field in spring or early sumer . before the start of the ,M. scutellatui oviposition

penod. Cerezke (1975) suggested stonng logs in high piles, and this was supported by the

presenc study, to reduce the arnount of surface area available for oviposition. Also. Iogs

should be stored in shade, as sugpsted by Post and Werner (1988).

Chapter Four: Oviposition behaviour and intra-specific competition of Monochamus scutellatus (Say) (Coleoptera: Cerambycidae)

Monochamus scutellatus (Say), the white-spotted pine sawyer beetle, is found

throughout North America with the exception of the cenual United States (Yanega 1996).

Males arrive fmt at logs, and guard positions on the log surface until arriva1 of the femaie.

Upon her amival. the male copulates repeatedly with her. often disrupting oviposition

(Hughes and Hughes. 1985). Eggs are deposited singIy in scars excavated in the bark of dead

and dying conifen. M e r emergeence. larvae feed in the phloem layer and eventuaily tunnel

into the heûrnvood of the log. where they continue to feed until pupation (Gardiner. 1957).

.4fier one to cwo yean, adults emerge and begin a period of maturation feeding on young

twigs and foliage (Rose. 1957). Oviposition site selection is important in this species. as

femaies leave the area shonly after oviposition. suggesting that propny have no parental

care.

Intra-specific competition has been determined to have an effect on the oviposition

biology of insects (e.0.. Schroeder, 1997; Prokopy et al.. 1984). Interference competition

generally involves direct access to a resource. Indirect interference may involve chemicd

cues that prevent access to a resource by other insects. whereas direct interference involves

contact between individuals. through temtoriaiity, cannibalism. combat. or suppression

(Prokopy et al.. 1984). For several insect species. females are able to differentiate between

areas that are available for oviposition, and those that have been expIoited or are otherwise

unsuitable. One way to avoid competition is through padtioning of a resource through

physicai or chernical means, which rnay act to reduce contact between individuals. and

maintain a Iow population density (Rausher, 1979). Chemical cues for avoidance of direct

competition rnay inclade oviposition detemng pheromones (ODP), which act intra-

specifically to alen fernales to the presence of another egg in the imrnediate vicinity

(Prokopy et al., 1984).

Sites seiectzd by fernales for oviposition cul have a sigifican~ effect on the survival

of her offspring, as hi& quality food resources and avoidance of competition at this stage

rnay increase size and robustness of offspring, thus increasing fimess of the female. To

optimize fimess, a female must be able to assess the presence and extent of threat from other

insects before oviposition. and this must be incorporated into the behaviourai sequence upon

amvai at a suitable hosr Because larvai survival rnay be influenced by predaton, parasitoids.

and cornpetitors. the evolution of host choice rnay be based on 'enemy-free space'. in which

survival is increased bv rhe absence of these factors (Thornpson. 1988).

In species of Monochus . an appropriate host is found through visud (ag,gregarion

of conspecifics, tree silhouette) or shemicai (pheromones or host volatile serniochemic~s)

cues (Chenier and Philogene, 1989b). After arriva1 at a suitable host. several factors rnay

influence femaie choice in site selecrion. including bark thickness (Nakamura et al.. 1995b),

presence of other insects. eggs or larvae (Anbutsu and Togashi. 1997a), or other signs of

oviposition by conspecific fernales. Fernale site choice rnay reduce larvd competition and

cannibaiism, as larvae wiU consume other eggs, or larvae, or will engage in combat resulting

in death of larvae if they encounter each other in the phloem region (Anbutsu and Togashi.

199%; Victorsson and Wikars. 1996).

Oviposition behaviour has k e n examined in several species of Monochamus in Nordi

America and Japan ( W f s h and Linit. 1985; Edwvds and Linit. 199 1; Jikumam et al.. 1994:

Anbutsu and Togashi. 1996, 1997&b; Shibata, 1984; Akbulut and Linit, 1999a&b; Zhang

and Linit, 1998). However, there has been no previous examination of oviposition behaviour

in M. scutellnrus. The objective of this study was to document the oviposition b e h a v i o d

sequence in M. scutellatus, and to examine factors influencing this sequence and oviposition

site selection after the fernale has anived at the log, such as the presence of eggs andor

irae under the k.t-


lnsects Al1 female and male M. scutellatur adults used in 1998 experiments were hand-

collected in June and July from red pine (Pinus resnosa Ait.) logs cut in the winter, c a 25

km NE of Thessalon, Ontario (46" 20' N 83" 33' E). In 1999. beetles were handcollected in

July and August from recently felled jack pine (P. banhiana Lamb.) logs at a clear-cut site

in Lawlor Township, ca 140 km NE of Thessalon, Ontario (47" 05' N 82' 50' E). Insecrs

were stored individually in screened plastic cages (12 cm long x 7 cm wide x 4 cm hi&) in

environmentai chambers set at 20" C, 16:s L:D, 70 % RH. Beetles were sexed in the lab or

the field based on antennal length described by Yanega ( 1996). The genitalia of 30 adult LM.

scutellanci beetles were dissected to confirm that antemal lene& could be used to identify

gender. Each beetle was provided with a jack pine twig and a 15 % aqueous sugar solution

on Cotton batting, and was caged for ca 2-3 days prior to the start of the experiments.

Oviposition behaviour To develop a description of the sequence of evenrs involved in oviposition.

preliminary behavioural observations were made at field sites in early- to mid-aftemoon.

when insecîs were rnost actively mating and females were laying eggs. In the laboratory.

behaviour was usually observed in early- to mid-afiernoon. under fluorescent Iighting at ca.

25°C. Male and female Uisects were placed in plastic cages (30 cm long x 20 cm high x 1 1

cm wide) containing a red pine bolt (10 x 10 cm) for oviposition. and a jack pine twig for

feeding. The various cornponents of oviposition behaviour were timed with a stopwatch.

Between one and four oviposition events were observed for each female.

Choice tests Five experiments were conducted to determine how the presence of eggs or larvae

affecteci the abundance and distribution of eggs by an ovipositing female. In al1 Experiments

in 1998 and 1999, a female beetle was given a choice between two bolts. In the fmt

Experiment, a female was given a choice between a control bolt (no eggs), and one which

contained her own eggs. The second Experiment was a choice test between a control bolt and

one which contained eggs from a different conspecific female. Experiment 3 was a choice

test between a control bolt and a bolt containing larvae from the snidy female. In the fourth

Experiment, a study female was given a choice between a control bolt, and one which

contained larvae from a different female. In Experiment 5, a female was given a choice

between a bolt containing her own eggs. and one conwining eggs from a different conspecific

female.

Preparation of bolts for choice tests Red pine logs (10 cm diameter) used in choice tests were cut prior to the LM.

sc r ï t e l l a~ flight season, in June 1998 or 1999. These were stored in the labontory at 25OC

until needed for study, c a 4 weeks after cutting. Log sections (bolts) measuring 10 cm in

length were eut fiom these as needed, and were labeled with permanent marker prior to

snidy. The bolts used in each choice test, one test and one control for 1998, and two tests in

1999, were contiguous fiom die same red pine log to ensure similarity in factors which may

influence oviposition site selection, such as bark thickness. phloem quality. rnoisture, and log

diame ter.

For dl five Experiments, female beetles were randomly assigned to 'same' or

'different' female groups. To obtain bolts containing eggs or Iarvae for Experiments 14 , red

pine bolts were intmduced to fernale beetles in both groups for oviposition, and were used in

choice tests after 3-5 days (to allow for egg development), or 2-3 weeks (to allow for l a n d

development). Those females in the 'different' group were allowed to oviposit on bolts for

2-3 days to provide eggs or larvae for use in funire Experiments. These bol& were then

labeled 'different fernale egg' or 'different female larvae'. These 'different' females were not

used for the purposes of examining experimental treatments, but some were used for

observation of oviposition 'behaviour. Thsse fernales t lat wcre to be used to examine

differences in egg abundance and distribution between treatments were also allowed to

oviposit for 2-3 days on bolts. These were labeled 'same female egg' (to be used after 3-5

days) or 'same female larvae' (to be used after 2-3 weeks). These bolts were later used in

choice tests involving a bolt containing the fernale's own eggs, or her own larvae. and a

convol boit that had nor been previously exposed to beetles. For Expenment 5, each bolt was

placed in a c a p with a test female or a different female for oviposition. and was removed

from the cage after a 74h period.

To conduct choice tests for Experiments 1 4 , a female was placed in a cage with two

bolts, a control. and one containing oviposition scars. A male beetle, a jack pine twip. and

sugar wster solution. were dso placed in the cage. The female was ailowed to oviposit on the

bolts for 48h, then both bolts were removed. For Experiment 5, two bolts, one containing

eggs from the tesr fernale. and one with eggs From a different fernale, were placed in a cage

with the test female and a male beetle for 48 houn for a choice test. A rest period of 24 houn

was given between each choice test. to reduce leming, experience and subsequent bias in

consecutive choice tests. In both study years, al1 females were used at lest once. and a

maximum of four times for choice tests, again to reduce the influence of expenence.

Copulation and oviposition behaviout were observed and documented sporadicaily over the

study period Bolts were then removed from the cage, and d l oviposition scm on the surface

were counted. Bolts were also examined for the presence of an 'oviposition plug', a brown,

sticky substance deposited in excavated scars and visible under a stereomicroscope.

Determination of the presence of eggs for choice tests On bolts used in choice tests, oviposition scars were marked with permanent marker,

and examined under a stereomicroscope for presence of a 'plug' prior to reintroduction of

bol& to the iemaie. The presznce or absencc af an oviposition plug. 3 stick; cjrovm substance

in the oviposition scar, could be an indication of oviposition. Fifty-three oviposition scars

were dissected by pulling the outer bark back from a scar until a 1 cm' area of phloem was

exposed If an egg was present, it was clearly visible within this area surrounding the scar.

and no funher dissections were necessary. Ninety-six percent (5 1 of 53) of scan containing

an egg also contained the brown sticky substance that was easily visible using a

stereomicroscope (SX mapification), and it was therefore assumed that if this piug was

visible. the scar contained an egg. Any scar without this plug was assumed to be empty. This

allowed determination of the presence of an egg in these scars without destroying the

oviposition site. The oviposition success (%) was calculated as the number of e g g deposited

divided by the number of scan excavated.

Statistical analysis Two-sarnple t-tests were used to examine differences in total arnount of time spent in

the oviposition behaviourd sequence by femafe beetles under field and laboratory conditions

(SigmaStat@, version 1.03. SPSS Inc.. Chicago. IL). ~urnben of scars cut and eggs laid. and

subsequent oviposition success. were cornpared between test and control bolts for each of

Experiments 1-4 with nvo-sample t-tests. For Experiment 5, two-sample t-tests were used to

examine the differences in number of scan cut, eggs laid and oviposition success in bolts

containing eggs from the same or a different female. Prior to the t-tests, data were

transformed by 1ogio (X + 0.5) to satise assumptions of normality and homogeneity of

variance (Zar, 1999), and dl subsequent analyses were performed on this transformed data

RESULTS AND DISCUSSION

Oviposition behaviour Observations were made of 35 oviposition events involving 14 females over a total of

13 hours in 1998, and of 23 oviposition events involving 13 females over a total of 22 houn

in 1999. The M. scutellatus oviposition behaviour sequence was observed and divided into

components fig. 4-1, Table 4-1). Of the 58 observarions, ten were of fernales in ihe field.

and the remaining 48 were of females under laboratory conditions. The components of the

sequence were similar, and followed the same order, in both the field and the laboratory, and

there was no significant difference between rotal amount of time spent on oviposition for

femaies under field or laboratory conditions (P = 0.269). Therefore. laboratory observations

were used for the remainder of the study.

The general oviposition sequence began when the femaie arrived at the log and began

to palpate on the bark surface with her Labial and maxillary palpi (sequence (S) 1 &2: Fig. 4-1

and Table 4- 1 ). The femaie excavated a scar in the bark with her mandibles once a suitable

oviposition site was found (S3). M e r excavation was complete. she tumed 180" (S4). uailed

her abdomen dong the surface until die scar was found (SS), and then inserted her ovipositor

into the newly excavated scar (S6). She then pumped her abdomen to deposit the egg under

the bark surface (S7), removed the ovipositor (SS), tumed 180' (S9), inserted her mandibles

again into the scar (S10). and then walked away (S 1 1). When alone. this sequence showed

Little variation for ail 27 fernales observed. and in most cases. eggs were deposited singly.

1 1) Fernale arrives at log 1

3) Chews/excavates scar in bark 1 f i

5) Trailing abdomen over area

6) Insertion of ovipositor into scar

1 7) Rimping of abdomen 1

1 8) Removal of ovipositor from scar 1

1 9) 180" turn I

10) Insertion of mandibtes into scar I

1 1 1 ) Fernale leaves area 1

Figure 4-1. Sequence of components of oviposition behaviour by female M. scutellatus beetles, based on 27 fernales observed over a total of 35 houn in 1998 and 1999.

ovipositor continues in a clockwise fashion, beginning here:

Figure 4-2. Components of the oviposition behavioural sequence of M. scutellatus, and percentage of total time devoted to each portion of the sequence. The sequence began with walking, and concluded with the insertion of mandibles into the scar.

Upon amval, a female walked over the surface of the Iog, paipating with her

maxillary and labial palpi, until a suitable oviposition site was found. A number of fernales

were observed inserting rnandibles into scars encountered during random walking over the

surface of the log. Dyer and Seabrook (1978) observed prolonged periods of palpation at

oviposition scars cut in the bark, and suggested that contact chemoreception may play a role

in site selection. One explanation for this is detection of an 'oviposition plug' containing an

oviposition detemng pheromone, or ODP. Anbutsu and Togashi (1997a) observed that

subsequent females that encountered scars left the area after palpation, suggesting that this

plug had a potentially deterrent effect on site selection. Thus, palpation by females in the

present snidy may have been to assess the status of the site, and also the presence of a plug in

any scars the femaie encountered. The plug potentially deterred femaies from oviposition,

and w u detected by palpation on the log surface.

Oviposition behaviour was similar in al1 female M. scutellanrs beetles observed in the

laboratory and field (Table 4-1). The behavioural sequence was not always uniforrn, but was

stereotypic, occumng in dl observed behavioural sequences (Brockerhoff et al.. 1999)

between waiking and excavating a scar, and remained so until removal of the ovipositor.

From this point, the sequence was probabilistic, and under the influence of numerous factors,

including the presence of other beetles. Insertion of rnandibles into the scar occuned in the

majority of observed cases, but was not as highly stereotyped as other behavioun.

Mandibular insertion after pumping of the abdomen was perhaps related to detection of an

oviposition detemng pheromone (ODP) in those scars that contained an egg. Anbutsu and

Togashi (1996, 1997a) observed the deposition of a jelly-like substance in oviposition scars

cut by female M. saftmrius beetles. followed by mbbing the scar with the tip of the

ovipositor. As every scar does not necessaily contain an egg, it would be expected that some

scars would not be plugged with pheromone. In such cases, the female would leave the area

without iuming and inserting her mandibles into the newly excavated scar.

Table 4-1. Behaviourd sequence associated with 58 oviposition events by female M. scurellanrs under field (n= 10) and laboratory conditions (n=48) in 1998 and 1999.

B ehaviour segment F~quency of segment Mean duation (sec) ic SE

1) Arrivai on log 2) WalkiDg/palpating 5 8/58 232.9 f 24.2 3) Excavation of scar 58/58 524.9 f 60.8 4) 180' tuni 58/58 6.5 + 0.8 5 ) Trailing abdomen 58/58 36.9 f 6.9 6) Insertion of ovipositor 58/58 10.7 t 1.2 7) Pumping of abdomen 58/58 328.9 f 37.8 8) Removal of ovipositor 58/58 7.1 k0.8 9) 180' mm 45/58 3.2 f 0.4 10) insertion of mandibles into scar 43/58 9.7 I 1.8 I I ) Leave area

The majority of tirne was spent in excavating the scar (45.2 %), and pumping the

abdomen in egg deposition (28.4 %) (Table 4-1, Fig. 4 2 ) . A female also invested a large

amount of time walking over the surface of the log. to find a suitable site for oviposition

(20.1 %). This suggests that a female invests the majority of her time in preparation of the

site, with her fimess depending on the adequacy of the site she has chosen.

All aspects of this oviposition sequence may be altered or intempted if a male beetle

is present in the cage with the femde. The majority of femdes completed the sequence

without interruption by the male (49 of 58 oviposition events). In one event, the female did

not complete oviposition. and in the other 8 events. the male slowed the progress of

oviposition. Male and femde beetles often encountered each other on the log surface, Ieading

to antennal thrashing, followed by the male initiating a 'half-mount' with the female prior to

copulation. The male remained in this position until dislodged by the female, regardess of

whether copulation had occurred. This dlowed the male to guard the femaie while she

located and excavated oviposition sites (Hughes and Hughes, 1982). In this position, the male

stood behind the female, with his forelegs on her elytra, following behind her on his mid- and

hind-Iegs. This slowed progress of the femde in locating suitable sites for oviposition, and

prevented her from moving to a more attractive portion of the log. At indetcrminste intervais.

the male copulated with the female, a process that lasted ca 30-45 sec. In one instance. the

male directly interfered with oviposition by mounting a female in the process of ovipositing

and immediately forcing her abdomen up out of the scar in order to copulate with her.

Effect of eggs on site selection

Control boit with no eggs vs. boit with eggs from same female (Exp. 1)

When females were offered a choice between control bol# with no eggs and bols

containing her own eggs, the number of scan excavated and number of eggs deposited on

both bolts was similar (Table 4-2). The differences between number of scars or number of

eggs were not significant between treatments (Table 4-2). Oviposition success (the

percentage of excavated s c m that contained an egg) was p a t e r on control bolts, but the

ciifference was not significant (Table 4-2). More than half of the total oviposition (54%)

occurred on control bolts (Fig. 4-3).

Table 4-2. Response of fernale M. scutellahu to bol& with or without eggs or lmae fiom henelf or a different female during laboratory choice tests, 19%.

Experiment Treatment No. of scars or eggs on No. of new No. of new Oviposition test bolts prior to scius eggs success (5%)

expenment (mean f SE) (mem t SE') (mean + SE) (mean k SE) Scars Eggs

f Test ' 8.4f1.8 6.341.6 5.1 k 1.r 3.2 F 0.8' 52.3 I9.5' Same femaie (N= 1 1)

eSg Control O O 4.7 C 1 .Oa 3.8 k0.6' 70.6 f 9.8' (N=ll)

2 Test 18.8k2.2 12.2515 1.7 f 0.4" 0.8 +, O.? 35.3 3 8.3' Difierent (N=27)

fernale egg Conml O O 8 . 1 + l . l b 5.7f1.0b 623f6 .1b RJ=27)

3 Test 11.9f1.6 8.8i1.3 3.1 C- 1.3a 2.3 f 0.7' 47.1 f 12.6' Same femaie (N=lO)

lvvae Controi O O 9.5 +. t,lb 3.320.7' 61.4+:10.Sa (N=lO)

4 Test 19.8kl.S t4.0t-1.4 35f0.6' 1 .S 2 0.5' 38.3 k 7.5' DBeren t (N=28)

fernale Iarvae Control O O 8.9 f l.ab 5.1 .t L .ob 53.9 k 6.8' (N=28)

L Means foilowed by the same leaer within a coIumn and Experiment are not sispificantly different rit P = 0.05 (log transformation of raw data, followed by a two-smple r-test). 'Test bolu are those containing eggs or larvae h m the same or a differenr femnle (see masends md melhods). Control bolu are those that had not k e n previously exposed to beetles.

Control bolt with no eggs vs. boit with eggs from different female (m. 2)

More scm were excavated and eggs deposited on conuol bolts, and the differences

between treatments were significant (Table 4-2). Oviposition success was significantly

higher on control bolts without eggs (62.3 %) than on bol& containing eggs fiom a different

fernale (35.3 5%) (Table 1-2). Eighty-seven percent of eggs were deposited on control bolts, a

significantly greaer number than that deposited on bolts containing eggs from a different

fernale (Fig. 4-3).

The presence of eggs from a different female deterred oviposition in choice tesu. as

fernales preferentially oviposited on a bolt that had not been previously exposed to another

female. This supports results from Anbutsu and Togashi (1996) who showed dia1 M.

altemhc~ Hope femaies were less likely to oviposit on bol& with oviposition scm,

especidy those with scan from a different female. This suggests that female M. scutellatur

beetles used cues in the immediate area of an oviposition scar to detect the presence of eggs.

and aiso to derennine if the progeny are her own, or from a different female.

In connast, in Experiment 1, no significant difference was seen in oviposition

betweea control logs and those with eggs from h e smdy fernate. Tne a u m k r of sxsavated

scars left empty was pater on test logs, indicated by a lower oviposition success on test

logs. This suggests that females did excavate scars on test bol& containing eggs, but they

oviposited in these scars with lower kquency than in scars on control logs. This may be

because they detected the presence of other eggs near newly excavated scars.

Effect of lawae on site selection

Contrd bolt with no larvae vs. bolt with larvae from same female (Exp. 3)

There was a sipificantly higher number of scan cut in control bolts than in bolts

containing larvae from the sarne female (Table 4-2): however, there was no sipificuir

difference between these two maments in the number of eggs laid or oviposirion success

(Table 4-2). The majority of eggs were laid on control bolts (60.8 %). but the difference was

not significant.

Control log L Test log *

Same femaie Different female Same female Different female

Figure 4-3. Percentage of total oviposition by M. scutellatus females on each of test and control bolts during laboratory choice tests. Those columns denoted by an asterix (*) have significantly different means at P = 0.05 (Two sarnple t-test).

Control bolt with no larvae vs. boit with /arvae fmm a dinerent female (Exp. 4)

When females were offered a choice between a control bolt and a bolt containing

larvae from another female, significantly more oviposition scars were cut and eggs laid on

the control bolts (Table 4-2). The number of excavated scan containing an egg was higher on

control logs (53.9 % vs. 38.3 % on test logs), but the difference was not significant (Table 4-

2). Seventy-five percent of oviposition occurred on control bolts, somewhat higher than that

for bolts containing larvae from the same femaie (Fig. 4-3).

In comparing Experiments 3 and 4, only the presence of larvae from a different

female acted to deter oviposition in choice tests, with females preferentially ovipositing on a

bolt that did not contain Iarvae. This supports Anbutsu and Togashi (1996), who stated that,

in M. altematus, fewer oviposition scars were found on bolts containing larvae, paaicularl y

when the larvae were From another fernale, however, the difference was not significant. This

would suggest that the deterrent effect was similar if the larvae were from the same or a

conspecific fernale. This may have been due to the presence of an oviposition detemng

pheromone, or to frass fiom feeding larvae, or the detection of reduced phloem availability

due to larvai feeding under the bark. These resuits suggest that the efkctiwness of 'S,e plug

as an oviposition deterrent decreased widi time after deposition, such that the difference

between plugs was negligible. The plug may have degraded with time. as at least 2-3 weeks

had passed between deposition and reintroduction to the female. The chernicd composition

or physical barrier of the plug may have changed or the plug may have been consumed by

emerging larvae.

Effect of eggs from the same or a different female on site selection

Bolt with eggs from same female vs. bolt with eggs from different female ( E x P m 5)

There were no sigificant differences between numbers of scan cut or eggs laid in

bolts prior to the choice tests (Table 4-3), ensuring that the baseline conditions for both

experiments were similar. When fernales were given a choice between a bolt containing her

own eggs or one containing eggs from another femaie, the difference in number of scars

excavated was not significant. There was. however, a significant difference in number of

eggs deposited (Table 1-3). There was no significant difference in oviposition success

between bolts containing eggs from the same or a different female pnor to choice tests (Fig.

4-4). However, there was a significant difference in oviposition success between sarne and

different fernale bolts after the choice tests (Fig. 4-4).

Table 4-3. Number of oviposition scars and eggs deposited in bolts presented to femaie M. scutellatus beetles during choice tests in 1999.

Experiment No. oviposition scan No. eggs deposited (mean f SEI' (mean I SE)

Same female Different femaie Sarne femde Different femde

Choice test 7.7 k 0.7a 6.3 +, 0.6a 6.6 L 0.6a 5. i +, O.Sb ' ~ e a n s foilowed by the same Ietter within a row for a meanired variable (rars, eggs) are not signikaotly different at P = 0.05 (two-sample t-test).

When given a choice between a bolt conraining her own eggs and one with eggs from

a different female, a femaie preferentially oviposited on bolts containing her own eggs. This

suggests that femaies recognize and avoid oviposition sites excavared by other females. This

supports results from Experiments 1-4, which suggested that a female was able to avoid

oviposition on bolts containing progeny from a different female with mate r frequency than

she would avoid a bolt containing her own. It may be adaptive for females to crowd

oviposition, which may lead to competition amongst her offspring, because even if combat

ensues, at least some offspring would be guaranteed to survive. However, it may be

advantageous for the femde to avoid competition with progeny from another female. If the

competing progeny were not siblings, survivd of at least some of her Iarvae could not be

guaranteed, particularly if the competing progeny were better adapted and cannibalism

Same Femaie Different F e d e Same Female Different Female

Re-tes t Choice Test

Figure 44. Oviposition success on red pine bolts by female M. sctuellatus beetles during labontory choice tests. Pre-test refers to oviposition on bolts by fexnaies prior to choice tests. Same fernale refers to oviposition on a boIt containing eggs from the test fende, and different female refen to eggs laid on a boIt containing eggs from a different fernale. There is a significant difference between oviposition niccess on bolts during the choice test ût P= 0.05. denoted by an asterix (*) (two-sarnpie r-test).

CONCLUSION

M e r amival on the log, female M. scutellam beetles walked over the surface,

palpating and assessing the suitability of the area During this process, the presence of an

oviposition deterring pheromone (ODP) may have acted to prevent oviposition in the

immediate area of eggs or larvae. Once a female had found a suitable site, the sequence of

behavioun involved in oviposition was generally stereotypic amongst aii females examined

in this study, until the ovipositor was removed. At that point, the female either turned to

insert her mandibles and perhaps deposit a pheromone into the scar, or left the area This was

likely tied to the presence of an egg in the scar.

Insects will preferentially oviposit on hosr plants on which potential larval survivai is

greatest (Rausher, 1979). so the ability to detect the presence of cornpetitors would act ro

reduce competition and improve larval survival. It has k e n observed that lmae of

~bfonochamus are cuinibalistic. and that cannibalism cm act as a great source of m o d i t y

(Rose. 1957; Victonson and Wikars, 1996). These larvae require a substantial amount of

available phloem and sapwood for Iarvai feeding. Survivonhip would therefore be gready

decreased if population numbers were high in any given are% AbiIity to detect eggs and/or

larvae at a potential site could improve survival, and oviposition could be detened by the

presence of other progeny.

Oviposition deterrence is adaptively sigificant in thai it allows fernales to avoid

areas that are dready k i n g exploited, and thus prevent competition for available resources

amongst offspring. Resource partitioning is particulvly important in an insect species such as

M. scutellattu, in which development of offspring and use of resources generally does not

begin until some tirne d e r the female has oviposited and lefi the arer If a female is able to

determine th= the area is unsuitable for further oviposition, she rnay increase the likelihood

of survival for her offspnng, and thus irnprove her own fitness by ovipositing elsewhere.

Oviposition desrrence has been demonstrated in a nurnber of species. including

species of Rhagolerlr (Prokopy, 1975). and BUW philenor (Rausher, 1979). This has been

the initiai observation in a number of studies investigating the presence and effect of

ovipositiondeterring pheromones (Xnbutjü and Togashi. 1996. 1997n; Kohno et d., 1986:

Prokopy et al., 1977; Quiring and McNeil. 1984; Renwick and Radke, 1980; and

Zimmeman, 1979). Resuits h m this study would suggest the presence of an oviposition

detemng pheromone for M. scutellatur. As this compound has been detected in the reiated

Asian species M. altemtzu, the presence of a brown sticky plug in scars excavated by M.

scutellarus and an avoidance of oviposition on logs containing progeny from the same or a

different female would suggest a chemicai deterrence. Further examination of the chemical

composition of this plug may determine if the plug acts as a physical or chemical barrier, or

if it is involved at ail. Behaviourai choice tests examining the plug may aiso determine the

role of the plug, and the potential for chemical oviposition detenence in this species. This

will also give a better understanding of avoidance cornpetition and its role in oviposition site

selection by female M. scutellatus beetles.

Chapter Five: Summary

The white-spotted pine sawyer beerle, Monochamus scutellarus (Say), is a major

contributor to wood decomposition in the boreal forest of Ontario. Larval feediog also results

in economic losses for logs lefi at cutting sites. Previous snidies have examined the life

history, economic importance, and reproductive behaviour of the species in Ontario and

elsewhere. This thesis presents information on the influence of chemical cues from the host

tree and cornpetition on oviposition by female LM. s c u t e l l a ~ beetles.

Attraction to suitable host plants by M. scutellancr was detennined by this snidy to be

chemicdly mediated. Beetles were attracted to turpentine and a-pinene. There was no

demonstrated effect of ethanol. a natural by-product of plant decomposition. Further smdy is

required to elucidate the relationship between ethanol and turpentine in attraction by male

and female beetles, as it was determined that ethanol has no synergistic effect at the release

rates snidied. An attraction or synergy with a-pinene has been demonstrated by other authon

in species of Monochamus. and further study would determine if the release rates used here

perhaps were too low to be detected by M. scurellanrs. There was a positive relationship

between increasing release rates of a-pinene and uap catch for femde M. scureilatus and

male M. mutator beetles. It is unclear why this reiationship was not seen for male Y

sctctellatw and femde LW mutatar. Further study widi higher a-pinene release rates would

also clarify attraction to this host volatile.

This study determined that both spatial and temporal segregation of resources occun

between M. scutellatus and other members of the phloem-feeding guild. The srndler species

had no appreciable effect upon survival and oviposition site selection by M. scutellatus.

However, 1. pini oviposited earlier in the season. so that ppmgeny of the fint generation could

84

emerge before foraging by M. scuteZZatus began. P. nemurensis was seen to have highest

larval swiva l in that portion of the log where M. scuteilntur was no: prevalent. Larger

species, such as M. scuteilatus, appear to be unaffected by the smaller and weaker species

under the bark and were able to exploit available resources. Niche partitioning. rhrough

spatial andor temporal segregation allows most insect species in the phloem-feeding guild to

avoid detrimental effects of competiuon, and improve fimess. Compritive axclusion a d

cornpetitive release can only be accurately demonstrated in a system fmm which one

cornpetitor has been mechanically excluded Further snidies into segregation should focus on

c w g Iogs to successfully remove M. scutellatus from the system. to obtain an accurate

p i c m of the behaviour and survival of I. pini and P. nemoremis in this system.

The oviposition behaviour sequence in M. scutellanis is stereorypic until afrer egg

deposition. and is probabilistic thereafter. Deposition of an egg in the scar appeared to

influence the remainder of the sequence. M e r pumping of the abdomen to deposit an egg,

females may not necessdly tum around and insert the mandibles into the hole. Further

research is required to determine if this action is connected to deposition of an oviposition

detemng pheromone (ODP) into the scar following oviposition. This study determined that a

female will avoid ovipositing near scars containing her own eggs or those from a different

female. She wiil avoid eggs from a different female with the greatest frequency. However, a

female will avoid her own larvae or those frorn a different female with equal frequency. This

susgests that the deterrent effect is not as strong 2-3 weeks after deposition of the chemical

plug. Further study into the chernical nature of the plug deposited into scars is required, as

weil as an examination of female deterrence based solely on this plug. as with a Y-tube

olfactometer,

Resource padtioning is particularly important in an insect species such as M. scurellam,

in which development of offspring and utilization of the resource provided by the female

p n e d l y does not begin until sorne time after the female has oviposited and lefi the area If a

femde is able to detennine that the area is unsuitable for further oviposition, she rnay increase

the likelihood of survivd for her offspring, and thus improve her own fimess by ovipositing

elsewnere. This process begins Mth detertion of chemicd cues in-flight, which give an

indication nor only of host tree species, but also of condition. Upon landing at the site. a female

must f i d an area that is fixe from competition with sirniiar-sized insects, or those that would

have sirniiar resource requirements and may reduce the chances of sumival of her offspring. The

cunivorous nature of larvai M. scutellatrcs reduces the requirement for avoidance of smaller

species. Further studies on the chernical ecology, naninl attack dynamics and influence of inna-

specific competition will give insight into the role of this beetle in the phloem-feeding guild.

A knowledge of the chemicai ecology of host selection in M. scutellarc~s cul be used to

determine which compounds act in attraction of beetles to suitabie hosts. This can then be

applied to developing apping programs to reduce the impact of M. scuteZ1atus at Iogging sites

and mil1 yards. As there is no demonsuated pheromone in the species, host volatiles are the most

prornising compounds for use in trapping. As these insects are attracted to hosts in a particular

stage of decomposition. understanding attraction to host volatiles and ethanol cm clari. the role

of M. scutelIorur in wood decomposition in the boreal forest. This smdy docurnented the

oviposition season and peak for this species. This is vaiuable for development of protocols for

removd of logs from field sites before oviposition begins. This may be useful in developing

protocols for stonng logs at field sites. in hi@ piles, to reduce the arnount of surface area

available for oviposition.

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