A NEW GENUS AND (COLLEMBOLA)downloads.hindawi.com/journals/psyche/1952/091898.pdfthird antennal segmentwithtwoshort, curvedrods directed anteromediad, and two adjacent guard hairs,

A NEW GENUS AND SPECIES OF ISOTOMIDAE(COLLEMBOLA)

BY PETER F. BELLINGEROsborn Zoological Laboratory, Yale University

In the course of an investigation of the soil fauna ofsome localities in Connecticut’, a number of species of Col-lembola were found which do not appear to have beendescribed. One of these is the subject of the present paper.Others will be dealt with in future contributions, as suffi-cient material becomes available.

Micrisotoma, gen. nov.

Vestiture generally .of short simple setae; a few curved,str,ongly serrate setae on all body segments, and some longsimple setae on the last tergite. Fourth antennal segmentwith blunt, cylindrical sensory hairs dorsally. Postantennalorgan broadly oval, with a thick border divided into equalarcs by four fine partitions. Eyes absent. Unguis andempodial appendage untoothed. Tibi,otarsus with a dstalsubsegment defined by an indistinct suture. Tenent hairsabsent. Fifth and sixth abdominal segments ankylosed.Manubrium with two pairs of setae ventrally. Dentesdorsally crenulate. Mucro bidentate. Pigment absent.

Generotype: M. achromata, sp. nov.

Micrisotoma achro,mata, sp. nov.

(Plate 2)

Numerous short, simple, curved setae on the head, ter-gites, and appendages. Outstanding, curved, serrate setae

Published with a gran flora t,he Museum of Co,mparatie Zoologyat Harvard College.

Carried out with financial assistance from the Connecticut Agri-cultural Experiment Station.

20

] Bellinger Isotomidae 21

are distributed as follows" one on each side of each thoracictergite; one on the base of the prothoracic leg; two to fiveon the bases o2 the mesothoracic and metathoracic legs;two or more pairs on each abdominal tergite, becomingmore numerous posteriorly. These setae (fig. 6) bear asmall number o strong, well spaced teeth.

The characteristic vestiture of the fused fifth and sixthabdominal segments is as ollows (fig. 8): mixed simpleand serrate setae in a line at the anterior border of thetergite, and at the sides posteriorly; dorsally, behind thisline, a straight transverse row o eight long, straight,simple, blunt-tipped setae (fig. 7); behind this row fivesimilar setae in a W-shaped line, two anterior and threeposterior; along the posterior margin a straight row of fivelong, straight, simple, sharp-pointed setae. Among thefirst two rows are scattered a number o2 very fine hairs;two additional fine hairs, oi which the anterior is minute,are just inside and in front .of each of the two lateral bluntsetae of the third row. On each side of the tergite, in thefirst row, is a short, broad sensory hair.

Antenna slightly longer than head; relative length .o+/-segments (expanded) 2:3:3:6. Fourth segment (fig. 1)enlarged, oval, ending in a blunt cone; dorsally with anumber of blunt, cylindrical sensory hairs. Sense organ ofthird antennal segment with two short, curved rods directedanteromediad, and two adjacent guard hairs, the ventralone straight, the dorsal curved and somewhat posterior tothe rods.

Postantennal organ (figs. 2, 3) longer than the greatestwidth o the second antenual segment (about 5:4), broadlyoval with a border about /3 of its greatest diameter inwidth; this border is interrupted at each end, and midwayon each side, by fine partitions. Eyes absent.

Unguis (fig. 4) moderate in length, curved, untoothed.Empodial appendage three-winged, more or less triangularwith acuminate apex; about / length of unguis. Tenenthairs absent. Tibiotarsus with an incomplete distal sub-segment; the suture is evident only ventrally.

22 Psyche [March

Ventral tube with about eight ventral setae. Rami oftenaculum quadridentate; corpus with one seta.

Manubrium ventrally with two pairs of strong setae nearthe distal margin. Dens twice length of manubrium; dorsal-ly crenulate in the middle third only, with about 16 folds;bearing a few fine setae dorsally and many ventrally. Mucro(fig. 5) bidentate, the apical tooth much the larger andstrongly curved; a medial lamella runs to the tip of theproximal tooth.

Fifth and sixth abdominal segments wholly ankylosed.Female genital opening a transverse slit, with anterior andposterior lips each bearing a pair of setae. Male genitalopening not seen.

Pigment wholly absent, except for the amber-coloredmouth parts.

Length of holotype 0.65 mm. Range (12 specimens) 0.4to 0.75 mm. The relative proportions of the segments maybe judged fr.om fig. 9; unfortunately specimens tend to besomewhat distorted in mounting, and the normal propor-tions cannot be determined.

The number of sensory hairs on the fourth antennal seg-ment varies from eight to eleven. The number of serratesetae varies somewhat also, but these are easily detachedand part of the variation may be apparent only. In onespecimen one ramus of the tenaculum is quinquedentate.

Holotype: "Cathedral Pines", Cornwall, Litchfield Co.,

EXPLANATION OF PLATE 2

Micrisooma achromaa. Magnifications approximate. Fig. 1. Dorsalview of left fourth antennal segment, holoype (700 X). Fig. 2. Rightposantennal organ, partype (700 X). Fig. 3. Right postantennal organ.pratype, transverse optical section (700 X). Fig. 4. Left hind claw addistul part of tibiotarsus, holotype (7{)0 X). Fig. 5. Left mucro a.nd endof dens, paratype (700 X). Fig. 6. Serrate seta from second abdominalsegment, holot,pe (700 X). Fig. 7. Blunt set from sixth abdominalsegment, holotype (7’00 X). Fig. 8. Fused fifth and sixth abdomlnalsegments showing arrangement of seae; somewhat diagrammatic(350 X). Fig. 9. ttolotype; outline, seae omitted. (120 X).

PSYCHE, 1952 VOL. 59, PLATE

BELLINGER ISOTOMIDAE

24 Psyche [March

Connecticut; taken in humus in a mature white pine-hem-lock stand, 19 December 1950.

Paratypes: same locality, October and December 1950;February, May, and August 1951. Eleven specimens.

Also taken once in humus under cedar’s in the outer zoneof an acid bog, Bethany, New Haven Co., Connecticut.

The holotype will be deposited in the Museum of Com-parative Zoology, Harvard University. One paratype willbe sent t.o the California Academy .of Sciences, San Fran-cisco, Calif., and one to the United States National Museum,Washington, D. C. The remaining paratypes are in theauthor’s collection.

Micrisotoma cannot be distinguished from other generaof Isotomidae by any single character. The form of thepostantennal organ will distinguish it from other isotomidsin the holarctic region, but Isotomina interrupta Schott,2rom Camerc.ons, is said to have a similar organ (Stach1947; the original description is not available to me), andsome species of Proisotom approach it in this respect(Folsom 1937, figs. 245, 216, and 273). The subsegmentedtibiotarsus allies it to Proisotoma BSrner, and the fusedabdominal segments and absence of eyes to ProisotominaSalmon; rom both genera it is distinguished by the pres-ence of serrate setae. In vestiture and general appearanceit resembles Isotomiella. Bagnall, which, however, lacks apostantennal organ.

Micrisotoma achromata appears to. be relatively uncom-mon in the two situations in which it has been found so far.It is possible that it is a marginal species in these areas,and that its environmental optimum is somewhat different.The species has not been seen alive; specimens in alcoholare indistinguishable ro.m Isotomiella minor Schaffer,which is common in the same samples.

BIBLIOGRAPHY

FOLSOM, J. W.1937. Nearctic Collembola or Springtails, of the Family Isotomide.

U. S. Nat. Mus. Bull. 168.

1952] Bellinger- Isotomidae 25

SALMON, J. T.

1948. Gollembola from the Three Kings Islands with a descriptionof Proiso.tomina, new genus. Pec. Aukland Inst. Mus., 3:291-300.

STACH, J.1947. The apterygotan fauna o,f Po.land in relation to the world

fauna of this group of insects. Family Isotomidae. ActaMonogr. Mus. Hist. Nat., Polish Acad. Sci. Letters.

MYSTRIUM IN AUSTRALIA (HYMENOPTERA: F,OtCMICIDAE).On July 8, 1951, in the company of Mr. William Bateman,Forest Officer for the Northern Territory of Australia, Icollected three workers of Mystrium camillae Emery atthe Howard River, north of Howard Springs, NorthernTerritory. This locality, southeast of Darwin, bears vege-tation of the type known as "tall open monsoon forest,"made up of the co-dominant trees Eucalyptus miniata andE. tetradonta, with cycads and various tall grasses con-spicuous in the understories. The ants were found be-neath a dry log very close to a termite colony. They layfeigning death for at least thirty seconds before beingput into alcohol.

The particular log from which the collection was madelay near, but not within, gallery forest of the type commonalong watercourses in the Darwin area. In such forest arefound many species of Indomalayan trees growing closeto the permanent moisture; these belong to such widespreadgenera as Terminalia, Pandanus, etc., and are intermingledwith large specimens of the paperbark, Melaleuca leuco-dendron. (I am grateful to Mr. Bateman for the botanicalinformation here greatly condensed.) This is the firsttime the genus Mystrium has been taken in the Australianregion. M. camillae has been taken at several po,ints insoutheastern Asia, from Burma through the East Indiesand the Philippines, and is the sole species found in thisarea. Several closely related species of the M. mysticumgroup occur on Madagascar.--WILLItM L. BROWN, JR.,Museum of Comparative Zoology, Harvard UniversiCy.

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A NEW GENUS AND (COLLEMBOLA)downloads.hindawi.com/journals/psyche/1952/091898.pdfthird antennal segmentwithtwoshort, curvedrods directed anteromediad, and two adjacent guard hairs,