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This article was downloaded by: [University of Newcastle (Australia)] On: 07 September 2014, At: 06:54 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK Journal of Natural History Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tnah20 Nesting biology of the spider wasps (Hymenoptera: Pompilidae) which prey on burrowing wolf spiders (Araneae: Lycosidae, Geolycosa) Darryl T. Gwynne a b a Department of Zoology and Entomology , Colorado State University , Fort Collins, Colorado, 80523, U.S.A. b Department of Biology , University of New Mexico , Albuquerque, New Mexico, 87131, U.S.A. Published online: 17 Feb 2007. To cite this article: Darryl T. Gwynne (1979) Nesting biology of the spider wasps (Hymenoptera: Pompilidae) which prey on burrowing wolf spiders (Araneae: Lycosidae, Geolycosa), Journal of Natural History, 13:6, 681-692, DOI: 10.1080/00222937900770511 To link to this article: http://dx.doi.org/10.1080/00222937900770511 PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms- and-conditions

Nesting biology of the spider wasps (Hymenoptera: Pompilidae) which prey on burrowing wolf spiders (Araneae: Lycosidae, Geolycosa )

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This article was downloaded by: [University of Newcastle (Australia)]On: 07 September 2014, At: 06:54Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registeredoffice: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK

Journal of Natural HistoryPublication details, including instructions for authors andsubscription information:http://www.tandfonline.com/loi/tnah20

Nesting biology of the spider wasps(Hymenoptera: Pompilidae) which preyon burrowing wolf spiders (Araneae:Lycosidae, Geolycosa)Darryl T. Gwynne a ba Department of Zoology and Entomology , Colorado StateUniversity , Fort Collins, Colorado, 80523, U.S.A.b Department of Biology , University of New Mexico , Albuquerque,New Mexico, 87131, U.S.A.Published online: 17 Feb 2007.

To cite this article: Darryl T. Gwynne (1979) Nesting biology of the spider wasps (Hymenoptera:Pompilidae) which prey on burrowing wolf spiders (Araneae: Lycosidae, Geolycosa), Journal of NaturalHistory, 13:6, 681-692, DOI: 10.1080/00222937900770511

To link to this article: http://dx.doi.org/10.1080/00222937900770511

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all the information (the“Content”) contained in the publications on our platform. However, Taylor & Francis,our agents, and our licensors make no representations or warranties whatsoever as tothe accuracy, completeness, or suitability for any purpose of the Content. Any opinionsand views expressed in this publication are the opinions and views of the authors,and are not the views of or endorsed by Taylor & Francis. The accuracy of the Contentshould not be relied upon and should be independently verified with primary sourcesof information. Taylor and Francis shall not be liable for any losses, actions, claims,proceedings, demands, costs, expenses, damages, and other liabilities whatsoever orhowsoever caused arising directly or indirectly in connection with, in relation to or arisingout of the use of the Content.

This article may be used for research, teaching, and private study purposes. Anysubstantial or systematic reproduction, redistribution, reselling, loan, sub-licensing,systematic supply, or distribution in any form to anyone is expressly forbidden. Terms &Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions

JOURNAL OF NATURAL HISTORY, 1979, 13 : 681--692

Nesting biology of the spider wasps (Hymenoptera: Pompilidae) which prey on burrowing wolf spiders (Araneae: Lycosidae, Geolycosa)

DARRYL T. G W Y N N E t

Depar tment of Zoology and Entomology, Colorado State University, For t Collins, Colorado 80523, U.S.A.

Introduct ion One of the most familiar groups of sand dune insects are the fossorial wasps which

are often observed digging or provisioning their nests. These wasps, mainly sphecids and pompilids, hunt for various types of ar thropod prey in a variety of places, often distant from the sandy area in which nest sites are located. A few species, however, Search the sand surface and locate certain types of prey which burrow beneath the sand. These species represent several families: scoliid wasps which prey on scarabaeid larvae (Evans and West Eberhard 1970) and certain sphecid wasps, Larropsis spp., which are searching for burrowing sand treader camel crickets (Gwynne and Evans 1975). Although these wasps represent different families t h e i r biologies are similar in tha t they move rapidly over the surface, antennating the ground and occasionally digging. When located, prey is not t ransported to a separate nesting burrow but is left paralysed in situ with a single egg. Certain species of a third family, the spider wasps (Pompilidae), move in a similar manner on the sand surface. Previous papers have reported that they are seeking burrowing wolf spiders, Geolycosa spp., as prey, the paralysed spiders being left in their burrows (Krombein 1953 a, b, 1958). The observations presented in this paper have revealed tha t two species, Anoplius marginalis (Banks) and A. cylindricus (Cresson) do use the spider's burrow but dig to extend the burrow. A third species, Pompilus scelestus Cresson transports the prey away from the burrow and digs its own burrow in the more typical pompilid fashion (see Evans and Yoshimoto 1962).

Materials and methods All three species of pompilids were present at the main s tudy site, the Great Sand

Dunes National Monument in southern Colorado. Observations were made there during the summer of 1976. Geolycosa rafaelana (Chamberlain) was the prey species. Some field observations were conducted during the summers of 1974 and 1975 in dune areas at 1%oggen, Weld County, Colorado and near Lamar, Bent County, Colorado. The prey species in these areas was G. wriffhtii (Emerton).

The three pompilid species were easily distinguished in the field: P. seelestus and A. marginalis are similar in size and black colouration but the latter species has a prominent dorsal basal orange stripe on the abdomen. A. cylindricus also has this orange stripe but is a smaller species.

Observations of the interactions between wasps and spiders were obtained by following the pompilids as they moved over the surface of the sand. Numerous man hours were spent following wasps a~nd during 1976 1 found that interactions could occasionally be set up by carefully collecting a searching female wasp with a net and

t Present address: Department of Biology, University of New Mexico, Albuquerque, New Mexico 87131. U..S.A.

0022-2933/79/1306 0681 $02"00 ~ 1979 Taylor & Francis Ltd

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introducing the wasp to an open Ueolycosa burrow. During 1974 and 1975 a few interactions between A. marginalis or A. cylindricus and their prey were initiated in the laboratory by introducing wasps into large jars of sand containing G. wrightii in burrows (for details of housing jars see Gwynne and Watkiss 1975). Interact ions between the spider and wasp could be observed through the side of the jar against which the Geolycosa burrow was usually constructed.

R e s u l t s The spider wasps were most active on the sand surface during the morning.

Activi ty dropped off by noon as the surface of the sand increased in temperature . All of the wasps searched tbr prey in a similar manner: moving in a sinuous fashion over the ground, eontinuMly flicking their wings and antennat ing the ground.

Spider burrows can be open or closed off with the web collar which surrounds the entrance (Gwynne and Watkiss: 1975). Although most observations were made when a spider wasp encountered an open burrow, they can apparent ly locate dosed burrows. In one observat ion an A. marginali8 located and squeezed through the web collar to enter the burrow. Occasionally a wasp would encounter a piece of web a short, distance away from the actual burrow and would become distracted. Some cues, probably chemical, are picked up from the web collar.

Both A. marginalis (mean size 15 ram) and P. scelestus (mean size 13"5 mm) prey on the larger instars (usually adult) of the spiders whereas A. cylindricus (mean size 8mm) pi~ys on smaller instars (wasp sizes from Evans 1951 a, b).

A noplius marginalis (Banks) This species was observed in all three s tudy areas mentioned above. A total of

nine field observations and six lab. observations were recorded for interactions between Geolycosa spp. and A. marginalis. All of the lab. observations and one of the field observations involved G. wrightii as prey. The eight remaining field observ- ations involved G. rafaela~a. Of" the 15 interactions seven went to completion (i.e., an egg was laid on the prey and the wasp left the burrow). This is not a good indication of the actual success of wasps due to the fact that, some of the interactions were in the lab. (of which three went to completion) and a few of the field interactions were set up as explained above. A reasonably complete nesting cycle was observed in three of the four successful field interactions and the three successful lab. interactions. Da ta on the initial interaction between wasp and prey were not obtained from observations in the field as the A. marginalis female, upon locating the open burrow, entered and usually did not reappear for a couple of hours when the nesting cycle was eomplete. Because I was able to see into the burrow of the spider, the lab. interactions provided most of the information on the interactions between wasp and prey. The following is an account of the nesting cycle of A. marginalis using Geolycosa as prey.

In nine interactions the wasp entered the open burrow without the spider coming to the entrance. On four occasions the spider was able to pull the web collar aeross the burrow entrance resulting in a closure and the wasp start ing to dig. Usually 'some dry sand would pour into the burrow and the spider would use its body to prevent sand from falling to the bo t tom of the burrow (see Gwynne and Watkiss 1975). This resulted in a plug of sand between the spider and the digging wasp. On two occasions the wasp gave up and moved away; during the Other two observations the wasp was able to dig down and enter the burrow. I f a thick layer of dry sand was present on the surface it was especially difficult for the wasp to dig into the burrow.

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Accurate times for the completion of the nesting cycle (from first entry of the burrow until the wasp emerged after laying the egg) were obtained from three field interactions for which the mean was 128 rain (see table 1). The only lab. durat ion which was recorded was 180 min.

When the wasp enters the burrow there is a brief struggle with t be prey during which the prey is stung on the ventral side of its cephalothorax and is then dropped to the bo t tom of the burrow. In one case (lab.) the spider left and was stung outside and dragged back into the burrow by the wasp. For a few minutes the wasp shows interest in the prey and maxala tes the base of the legs, mouthpar t s and venter (possibly where the sting entered). Occasionally the wasp probes the r en t e r of the prey with its abdomen; conceivably re-stinging of the prey occurs at this point.

F rom 5 to 11 rain (N = 3) after the prey is stung, a side burrow is initiated by the wasp. In all lab. interactions this burrow was star ted at the bot tom of the spider 's burrow (Geolycosa housed in lab. containers dig their burrows to the bo t tom of the jars; burrows in the field are usually deeper) and constructed a t approx. 90 ° to the burrow. Three nest excavat ions in the field, however, showed tha t the side burrow star ted pa r t -way down the prey ' s burrow. The side burrows in field excavat ions could not be traced because they were filled by the wasp. However, much of the spider's burrow was below the level of the cell (fig. 1 ) so the side burrow is presumed to go straight from the main burrow to the cell as it does in the A. cylindricus nest (see below). Both the depth of the cell and its distance from the main burrow were remarkab ly constant in the three field excavat ions (see table 1 for dimensions). Apparent ly a certain depth is appropr ia te for the construction of the cell. In the lab. the wasp was prevented from reaching this depth so the side burrow and cell were constructed along the bo t tom of the housing jar.

The paralysed prey was usually placed at the entrance to the side burrow while the wasp was digging. In the lab., excavated sand was often pushed out through the entrance to the spider's burrow. This did not happen in the field, however, excess sand probably falls into the portion of the spider 's burrow below the level of the side burrow. Excava ted sand was pushed out from the side burrow approximate ly every 30 s, Most of the t ime needed to complete the nesting cycle is involved with the excavat ion of the side burrow and the construction of the cell at the end of this burrow.

Table 1. Anoplius marginalis nest data.

Time to complete Geolycosa nest cycle burrow Length of side Cell depth (minutes) depth (cm) burrow (cm) (cm) Egg position

Dorsolateral on - - 18 18 15 left anterior part

of abdomen Lab. 180 15 15 15 Same--right

Larva already - - 15 15 15 hatched

104 . . . . 155 42 8 20 Same--left Field 1 2 5 3 2 12 2 0 - - - - - - 10 18 Same--right

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F~G. 1. Side view of a typical field nest of A. marginalis (length of reference bar = 5 cm).

The details of cell construction and oviposition are unknown; in the lab. the cell was always constructed away from the side of the glass jar. At some point the paralysed prey is moved along the side burrow and is positioned in the cell. In the interaction, which lasted 155 min, the spider was dragged into the side burrow 99 min after the wasp first encountered the prey 's burrow. Apparent ly about an hour is needed for the final excavat ion of the cell, positioning of the prey and oviposition.

Since I was not able to trace the side burrows in field excavations of four successful nests, these burrows had presumably been filled by the wasp. Side burrows were, in fact, filled in two successful lab. nests. In three of four field observations the A. ma~yinalis female moved sand into the spider burrow as she emerged. However, spider burrows in both field and lab. were usually only part ial ly filled (fig. 1).

Excava t ions of two uncompleted nests in the field showed tha t no side burrows had been constructed; for unknown reasons the wasp had abandoned the prey in the main burrow. No egg had been laid in either case.

The position of the egg on the prey was determined in four of the six excavations of completed A. marginalis nests. The egg was always laid dorsolaterally near the anterior par t of the spider 's abdomen, either on the left or right. This egg position was reported by Evans and Yoshimoto (1962) and Krombein (1964) for this species

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(table 1, fig. 2). Spiders removed from excavated cells recovered from paralysis within two hours after the nest cycle was completed.

Two larvae were successfully raised in the lab. ( temperature approximate ly 24°C). In four days the larva hatched and grew rapidly so that by the fifth day it was about half the length of the spider 's abdomen (about 8 mm). By the ninth day most of the prey had been consumed. Ten days after oviposition the final instar larva spun a c o c o o n .

Anoplius cylindricus (Cresson) Interact ions between this species and its prey were especially d i~cul t to observe

due to the small size of both predator and prey. Some of the wasps observed in the field were as small as 4 m m in length. The only complete interaction was one observed in the lab., al though three other observations were made in the field at Roggen, Colorado.

Two of the field obsel-cations showed the spiders' burrows to be open when first located by the wasp. In all observations, both field and lab., the wasps were able to dig their way into the burrows. Two of the field observations were terminated by the wasp within 30 rain of the wasp entering the burrow. In one of these I excavated a small paralysed spider about 6 cm down in its burrow; no egg was located on the prey. In the other field observat ion the wasp emerged after 25 min and filled the burrow. I was not able to locate any prey. When the wasp first entered the burrow in the remaining observation, a small Geolycosa ran from the burrow mouth. The wasp caught and stung the spider about l0 cm away. The paralysed prey was dragged back to the burrow. A strong wind was blowing and while the wasp entered the burrow the prey was moved by the wind. The wasp subsequently became disoriented and abandoned the prey.

The interaction in the lab. lasted 120 min from first entry of the A. cylindricus into the burrow of her prey. Prey stinging and the other events in the interaction were very similar to those observed for A. marginalis. Prey was stored 7 cm down in the burrow; a side burrow was initiated 2 cm below the prey and 7 cm above the bo t tom of the spider's burrow. Excava ted sand was pushed out into the spider's burrow below the level of the side burrow. During the excavat ion the prey was occasionally checked and 85 min after the wasp first entered, the prey was taken into the side burrow. The wasp appeared 20 min later, gradually filled both the Side and main burrows, and finally emerged. The side burrow was 8 cm long and was at right angles to the main burrow (same structure as the A. marginalis field nest, see fig. 1). No egg was located on the spider; however, it could have been removed during my excavat ion of the Cell.

Pompilus scelestus (Cresson) Observations on this species were made a t the Great Sand Dunes Nat ional

Monument during 1976. Eight interactions between wasps and their prey, G. rafaelana, were recorded. Details of the complete nesting cycle were obtained from three successful nestsl In one of these the wasp was first located digging its separate nesting burrow, having already obtained its prey. A fourth observat ion s tar ted with prey capture but ended when the prey, which had died in the hot sun, was abandoned. The other four interactions were terminated even earlier, usually because the prey escaped.

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Fins. 2-5. (2) Position of the A. marginalis egg on G. rafaelana. (3) P. scelestus digging at nest entrance. (4) P. scetestus dragging G. rafaelana prey. (5) Venter ofG. rafaelana showing position of the P. scelestus egg.

Unlike the two species of Anopl ius previously considered, P. scelestus removes the spider from its burrow and behaves in a more ' typical pompilid fashion' by digging its own burrow.

Upon locating an open burrow the P. scelestus female usually antennates the web collar and slowly enters. E n t r y did not seem to be as quick as in A. marginalis. In three interactions the wasp left quickly and re-entered the burrow a few times. After leaving, the wasp would often remain motionless near the burrow and press its body to the sand surface. In all three interactions the spider came to the burrow mouth. In two cases there was a brief struggle and one of these resulted in the spider being stung by the wasp. For unknown reasons this wasp became disoriented and abandoned the prey. In the second case the wasp was not able to sting the spider which closed its burrow by pulling the web collar over the entrance. The wasp dug in the dry sand around the burrow mouth for 32 min before giving up. In the third interaction the wasp advanced toward the spider which had appeared at the burrow mouth. The spider pulled its web collar and blocked the burrow. The wasp subsequently abandoned the site after several a t t empt s at digging. On one other occasion I saw a female digging vigorously. She dug for a few minutes before giving up. I dug in the area and located an active spider in its burrow. The initial enter-exi t behaviour of the wasp apparent ly serves to lure the spider to the burrow mouth.

In another two interactions the wasp was not able to lure the spider to the burrow- entrance. The wasp re-entered and stung the spider in its burrow: in one ease a fully paralysed spider was dragged out, in the other the spider still showed slight movement and was re-stung just outside the burrow mouth.

The t ime taken for individual P. scelestus females to complete nest cycles were extremely variable. Accurate t imes were recorded for two successful nests (table 2). One wasp was observed to take 8 hours 7 min until nest completion. Another interaction, mentioned above, lasted for 5 hours 55 min. from prey capture until the dead prey was abandoned. The apparen t reason for these long durations was the thick layer of dry surface sand; females were continually abandoning a t t empted burrows which collapsed during excavation.

Once the prey is removed from the burrow it is dragged to a nearby plant and is usually suspended a few centimetres off the ground in the vegetat ion (see table 2).

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Table 2. Pompilus scelestus nest data.

Distance from prey Mean time between Time taken to Prey storage storage to wasp prey-checks

complete nest cycle location (minutes) burrow site (m) (minutes)

__ 10 em off ground 0.2 4-4 (N--5) in rabbitbrush

487 2 cm off ground in 5 dry grass

115 5 em off ground in rabbitbrush 5 13-3 (N--4)

355 (until prey In shade of grass abandoned) stems 4 6"3 (N=4)

Time to complete Time of re-stings nest after prey is Length of burrow Depth of cell of prey (minutes) taken into burrow entrance (cm) (cm)

(minutes)

No re-stings 37 10 9-5 79 40 15 9 90 27 17 12

28 and 97 Dead prey abandoned - -

Storing the prey in this manner would reduce the chance of it being taken by other insects and also serves to keep the prey out of the hot sun. At this point the wasp leaves to look for a nest site, often testing numerous places before starting to dig a burrow (fig. 3). Frequent trips are taken from the burrow site to check the prey (see table 2). Prey are occasionally re-stung, especially in those observations where the wasp takes a long time to locate a nest site (see table 2 for times of prey re-stinging). Re-stinging usually takes place after some observable movement of the prey's appendages during a prey-check. During those observations which continued until noon or thereafter, the wasp was often observed to escape from the hot sun and remain motionless in the vegetation near the prey.

At some point, when a successful burrow has been dug, the wasp drags the prey by the base of one of its legs (fig. 4) toward the burrow site. Occasionally the prey is left while the wasp flies ahead to check the burrow. The prey is then dragged into the burrow. The burrow is filled and the wasp occasionally does some levelling on the nest site. The time taken from when the prey is taken into the burrow until the final closure was qmte consistent in the three interactions (X = 34"6 rain, see table 2).

T-he nest construction is of the typical pompilid type (Evans and Yoshimoto 1962) with a single cell (mean depth 10-2 era) at the end of a short entrance burrow (mean length 14 cm) (see table 2).

The egg is laid in a specific location; in all three nests it was transverse across the venter of the spider's abdomen, in the same position recorded by Evans (1970) and Kurezewski and Kurezewski (1973) for this species (fig. 5).

At the Great Sand Dunes, during 1976, I excavated several Geolycosa burrows. Most of these burrows contained spiderlings which cluster tightly on the mother 's abdomen as shown by Rovner et al. (1973). When a burrow is entered by an A. marginalis or P. ,s'cetestus female the spiderlings leave the mother and move out through the burrow entrance. This was observed on seven different occasions. In

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three of these the spiderlings were still moving out of the burrow several hours later when the A. marginalia was filling the host 's burrow after completing her nest.

Discuss ion Pompilid predators of Geolycosa are not always successful in subduing a spider

prey. Observations have revealed that the spider has certain defensive moves, such as 'collar pulling' and maintaining a plug of sand between it and the wasp. This makes it more difficult for the waso to get at its prey.

The two species of Anovlius differ from P. scelestus in their ability to use the spider's burrow as the nesting site. Use of the prey's burrow no doubt reduces possible prey stealing by surface scavengers and cleptoparasites. The Anoplius do, however, construct a short side burrow from the main burrow to the cell. This also is probably a strategy to avoid certain nest parasites. I f the pompilid female is able to locate a closed burrow by using cues from the spider's web collar then conceivably nest parasites can also use these cues (cues which would not be present at the entrance to a typical pompilid burrow). Certain species of miltogrammine flies (Sarcophagidae), velvet ants (Mutillidae), cuckoo wasps (Chrysididae) and the pompilid genus Evagete8 (cleptoparasitic on other pompilids) locate fossorial nests and dig down to the cell to lay their own eggs. Positioning the cell some distance from the main burrow would probably reduce the success of these natural enemies. This hypothesis is supported by the observation that the side burrow is always filled whereas the main burrow is often only t)artiallv filled (fig. 1).

One intriguing aspect of the biology of all spider wasps and other fossorial wasps is the species-specific position of th'e egg on the prey. In certain sphecid wasps which prey on burrowing Orthoptera (which recover from paralysis) the egg is laid in a position so that the digging legs will not inteI'fere with the developing larva (Gwynne and Evans 1975). All pompilids oviposit on the spider's abdomen (Evans and Yoshimoto 1962) where the cuticle is thin and the eclosing larva can penetrate the body wall easily. However, the species-specific position of the egg on the abdomen remains a mystery.

A number of studies have described various aspects of the biology of pompilid wasps (see review by Evans and Yoshimoto 1962). Although the paper by Evans and Yoshimoto presents a taxonomic list of spiders and their respective pompilid predators, no Studies have taken a particular spider group and examined the biologies of the pompilids which prey on it. The burrowing wolf spiders form a good 'natural group' not only because of certain morphological characters (Kaston 1948) but also because of their burrowing habits: spiders of the genus Geolycosa rarely leave their burrows in the soil, and prey on insects which pass close to the burrow entrance (Wallace 1942). Other lycosids are known to use burrows but they are not nearly as denendent on the burrow as Geol,tcosa.

Four species ot spider wasps, Anoplius relativus (Fox), A. marginalis, A. cylindricus and Pompilus scelestus, are known to take species of Geolycosa as prey. This paper has presented more detailed information on the lat ter three of these species. Based on previously published prey records plus those presented here, fig. 6 shows the predator-prey relationships of the four pompilid species with both Geolycosa prey and other known spider prey. I t also includes the habitat range of the wasps and all the species of prey.

Evans and Yoshmito (1962) have concluded that pompilid wasps are poor 'spider taxonomists ' but good 'spider ecologists' in tha t they take an appropriate size of prey

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F~G. 6. Predatoi~prey relationships of the fbur pompilid species which prey on Geolycosa. Prey records for other spider species are included. Other prey records from: Evans (1951 a, b, 1970)~ Evans and Yoshimoto (1955, 1962), Kurczewski (1962), Kurczewski and Kurczewski (1968 a, b, 1973), Krombein (1953 a,b, 1958, 1964) and Wasbauer and Powell (1962). Also shown are the habitat types of wasps and prey (the dotted line refers to a record where habitat types of wasp and spider were not consistent). Habitats of Pompilidae from Evans (personal communication) and Evans and Yoshimoto (1962). Habitats of spiders from Emerton (1912), Fitch (1963), Kaston (1948, 1953), Lowrie (1948) and Wallace (1942).

from the habitats in which they hunt but rarely stick to a particular taxon of spiders. P. scelestus (fig. 6) is commonly found in habitats ranging from sand dunes to wooded areas and preys on large spiders within those habitats (mostly lycosids, although other prey records for this species include 'Ly<'osa spp.' and a salticid spider. 'Phidippus spp'; fig. 6 includes only prey identified to species). A. relativus also has a wide range of habitat types and utilizes a number of different spider groups as prey. Both P. scelestus and A. relativus dig their own burrows and do not use the burrow of the spider when using Geolycosa as prey. A. marginalis is narrower in its range of habitats and is known to prey on other lycosids as well as Geolycosa. When using these other lycosids A. ma~yinalis does dig its own burrow (Evans and Yoshimoto 1962) but has the ability to use the spider's burrow when preying on Geolycosa. A. cylindricus, on the other hand, is only known to prey on Geolycosa, is not known to dig a separate nesting burrow and is only found in sand dune areas. Interestingly enough, this species is a member of the subgenus Pompilinus which have weakly developed tarsal combs (used for digging). Other members of this subgenus are known to utilize other species' burrows for their nest sites (Evans, personal communication). These four species appear to form a continuum with respect to habitat and prey type: from A. cylindricus, which is restricted in habitat and prey type, to P. scelestus, which has a wide spectrum of habitats and prey.

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Nesting biology of the spider wasps 691

I f a prey resource is abundan t and occurs in a predictable location it might pay a spider wasp to specialize on t ha t prey. Geolycosa spp. are certainly abundan t in all dune areas visited in Nor th America (Gwynne, unpublished). Apparent ly A. cylindricus is a spcciaiist on this group and h a s evolved to use the prey most efficiently by using the burrow. A. marginalis appears to be tending toward specialization on Geolycosa as it is most frequently reported to take this genus as prey and also uses the prey 's bmT0w. However, it does retain the ability to take other lycosids and to dig its own burrow when necessary (see also the discussion by Evans (1953)). In contrast , P. scelestus (and probably A. relativus) is not nearly as efficient in using burrowing wolf spiders as prey. This species invests much t ime and energy in moving the prey away from the burrow and digging a separate nest. I t can take most of the day to complete a nesting cycle (table 2), compared to a couple of hours for A. cylindricus and A. marginalis (table 1). During this t ime the prey is in termit tent ly stored and dragged across the sand. I t is exposed to other scavenging insects and especially to cleptoparasitic spider wasps and other pompilids which might usurp the prey. One individual o f P . scelestus was seen to interact twice with a cleptoparasitic pompilid, Evagetes hyacinthinus Cresson (which digs into the host ' s nest), once with a Ceropales sp. (which inserts its egg into the. booklungs of the host 's prey) and once with an A. marginalia female. All this took place within the long nesting cycle of this part icular P. scelestus. The other d isadvantage of t ransport ing the prey away from its burrow is the exposure to the hot sun which, in one interaction (see above) killed the prey.

A. n~rginalis and P. scelestus both take the same sizes of spider prey: if no other prey were available to these two species and Geolycosa was a limiting resource, A. marginalis would easily outcompete P. scelestus due to the efficiency of the former species in her nesting habits. This is not the case, however, because the two species appear to utilize different strategies: (1) to specialize more on a predictable prey in a specific hab i ta t and (2) to take a range of prey types from a var ie ty of habitats .

Summary Four species of pompilid wasps are known to prey on the burrowing wolf spiders,

Geolycosa. Observations were made on the nesting biology of three species, Anoplius cyli~Mricus, A. marginalis and Pompilus scelestus. The wasp species appear to form a cont inuum of habi ta t and prey selection types (fig. 6). A. cylindricus is restricted in habi ta t and is only known to prey on Geolycosa. A. marginalis occurs in a wider range of habi ta ts and preys on Geolycosa and other lyeosids. Both species of Anoplius modify the Geolycosa burrow to form a nest. P. scelest~ts has a wide range of habi ta t and prey types and when preying on Geolycosa mores the spider from its burrow to a separate nest site.

Acknowledgments I am grateful to Dr. Howard Evans, Kei th Christian and Kevin O'Neill for their

discussion and criticism. I would also like to thank Dennis Huffman and Debbie Organ of the U.S. National Pa rk Service for their help during my s tay at the Great Sand Dunes National Monument, Colorado. The pompilid wasps were identified by Dr. Evans and voucher specimens of wasps and spiders have been deposited in the collection of Colorado State University. This s tudy was supported by N.S.F. grant (BNS76-09319) to Dr. H. E. Evans.

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692 Nesting biology of the spider wasps

R e f e r e n c e s EMERTO~, J. H., 1912, Four burrowing Lycosa (Geolycosa Montg., Seaptosa Banks) including

one new species, Psyche, 19, 25 36. EVANS, H. E., 1951 a, A taxonomic study of the Nearctie spider wasps belonging to the tribe

Ponlpilini (Hymenoptera, Pompilidae). Part II: Genus Anoplius Dufour, Trans. Amer. Ent. Soc., 76, 207-361. 1951 b, A taxonomic study of the Nearetie spider wasps belonging to the tribe Pompilini (Hymenoptera, Pompilidae). Part IIi , Trans. Amer. Ent. Soc., 77, 203-240. 1953, Comparative ethology and the systematics of the spider wasps, Systematic Zool., 2, 155-172.

- - 1970, Ecological behavioral studies of the wasps of Jackson Hole, Wyoming, Bull. Mus. Comp. Zool.~ 140, 451-511.

EVANS, H. E., and YOSHIMOTO, C. M., 1955, An annotated list of pompilid wasps taken at Blackjack Creek, Pottawatomie County, Ka~sas (Hymenoptera), J. Kansas Ent. See., 28, 16-19. 1962, The ecology and nesting behavior of the Pompilidae (Hymenoptera) of the Nol%heastern United States, Misc. Publ. Ent. Soc. Amer., 3, 65-119.

EVANS, H. E., and WEST E~ERHARD, M. J., 1970, The Wasps (Ann Arbor: University of Michigan Press), 265 pp.

FITCH, H. S., 1963, Spiders of the University of Kansas Natural History Reservation and Rockefeller Experimental Tract, University of Kansas Publs., Mus. Nat. Hist., 33, 1 102.

G\vY~N]~, D. T., and EvAns, H. E., 1975, Nesting behaviour of Larropsis ehilopsidis and L. vegeta (Hymenoptera: Sphecidae: Larrinae), Psyche, 82, 275-282.

GwY~E, D. T., and WAT~ISS, J., 1975, Burrow-blocking behaviour in Geolycosa wrightii (Araneae: Lycosidae), Anita. Behav., 23, 953-956.

KASTON, B. J., 194=8, Spiders of Connecticut, Conn. Geol. Nat. Hist. Survey Bull., 70, 1-874. 1953. How to Know the Spiders (Dubuque, Iowa: Win. C. Brown), 289pp.

K~OMBEIX, K. V., 1953 a, Biological and taxonomic observations on the wasps in a coastal area of North Carolina (Hymenoptera: Aeuleata), Wasmann J. Biol., 10, 257-341. 1953 b, Kill Devil Hills wasps, 1952~ Prec. Ent. Soc. Wash., 55, 113-135. 1958, Biological notes on some wasps from Kill Devil Hills, North Carolina, and additions to the faunal list, Prec. Ent. Soc. Wash., 60, 97-110. 1964, Results of the Archbold Expeditions. No. 87: Biological notes on some floridian wasps (Hymenoptera, Aeuleata), Amer. Mus. Novit., 2201, 1-27.

KURCZEWSKI, F. E., 1962, Observations, including new prey records, of some Nearctic Pompilidae (Hymenoptera), Bull. Brooklyn Ent. Soc., 57, 85-90.

KURCZEWSKI, F. E., and KURCZEWSKI, E. J., 1968 a, Host records for some North American Pompilidae (Hymenoptcra) with a discussion of factors in prey selection, J. Kansas Ent. See., 41, 1-33. 1968b, Host records for some North American Pompilidae (Hymenoptera). First supplement, J. Kansas Ent. See., 41,367-382. 1973, Host records for some North American Pompilidae (Hymenoptera). Third supplement: Tribe Pompilini, J. Kansas Ent. Soc., 40, 65 81.

LowmE, D. C., 1948, The ecological succession of spiders of the Chicago area dunes, Ecology, 29, 334 351.

ROVNER, J. S., HIGASHI, G. A., and FEOLIX, R. F., 1973, Maternal behavior in wolf spiders: the role of abdominal hairs, Science, 182, 1153-1155.

WA~I~ACE, H. K:, 1942, A revision of the burrowing spiders of the genus Geolycosa (Araneae, Lycosidae), Amer. Midl. Nat., 27, 1-62.

WASBAUE~, M. S., and POWgLL, J. A., 1962, Host records for some North American Spider wasps, with notes on prey selection (Hymenoptera: Pompilidae), J. Kansas Ent. Soc., 35,393-401.

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