Wirth, W.W.

Proceedings of the Hawaiian Entomological Society

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Vol. XIV, No. 3, March, 1952 415Two new Spider Egg Predators from the Hawaiian Islands(Diptera: Drosophilidae)By WILLIS W. WIRTHBUREAU OF ENTOMOLOGY & PLANT QUARANTINEAGRICULTURAL RESEARCH ADMINISTRATION, U. S. DEPARTMENT OF AGRICULTUREWhile rearranging the collection of Drosophilidae in the U. S. NationalMuseum, I discovered a short series of flies from the Hawaiian Islandswhich apparently belong to an undescribed species of Titanochaeta. Thisgenus was erected by Knab (1914, Insecutor Inscitiae Menstruus 2:168)for a single species, ichneumon Knab, which had been reared from spideregg-sacks on sugar cane from Mountain View, Hawaii.Through the courtesy of D. Elmo Hardy and E. H. Bryan, Jr., some ofthe drosophilids which Swezey reported in 1929 (Proc. Hawn. Ent. Soc.7:292) that he had reared from spider egg cases from Oahu, were locatedand borrowed for study from the Bishop Museum collection. These alsoprove to be new and are described below.With the discovery of these two additional species it is reasonablyapparent that Titanochaeta is an endemic genus in Hawaii, another caseof a very ancient natural introduction having broken up into species ondifferent islands. It would be very interesting to make collections fromother islands to determine how far this speciation has gone.Titanochaeta swezeyi Wirth, new species#, $. Length about 3 mm., wing 2.7 mm.Subshining yellow, bristles and hairs black; face, cheeks, mesonotum, scutellum andpleura whitish pruinose; frons more or less dull brownish-yellow, ocellar triangle andfrontal orbits whitish pruinose; abdomen brownish above; wings brownish hyaline, theveins yellowish, both crossveins dark brown.Frons a third as wide as head, slightly converging toward antennae; ocellar triangleand orbits well differentiated but not raised, with sparse, fine short hairs; middlefronto-orbital bristle three-fourths as long as the anterior, half as long as posteriorfronto-orbital, much stronger than in ichneumon. Antenna entirely yellow, arista withonly two or three rays. Face not as concave as in ichneumon, the median carina distinct; cheeks broader, about a fifth of eye height in male, slightly narrower in female;postocular hairs stronger. Eyes with interfacetal hairs rather sparse and short.Humeri each with a strong bristle and a second shorter one just below; sternopleuronwith two strong bristles and a few fine hairs. Mesonotal hairs coarse, suberect and non-seriate; scutellum with anterior marginals divergent, slightly longer than the strong,cruciate, posterior pair; four or five short hairs on each side of scutellum. Legs withstrong posterior bristles on fore femora,-otherwise as in the genotype.Female wing with second section of costa 2.8 times as long as third (costal index);ultimate section of fourth vein 3 times as long as the penultimate section (fourth veinindex); hind crossvein 0.75 times as long as penultimate section of fourth vein and 0.75times as long as ultimate section of fifth vein. Male wing (figure 1 a) with costal index2.7, fourth vein index 4 to 5, and the hind crossvein much more oblique, being 1.1times as long as penultimate section of fourth vein and 0.6 times as long as ultimatesection of fifth vein. End of first section of costa with two long, differentiated bristles.416 Proceedings, Hawaiian Entomological SocietyHolotype 2 , allotype, and 1 $ and 1 $ paratype, Haiku, Maui, Hawaiian Islands, August, 1918, J. C. Bridwell (ex spider egg mass) (Typeno. 61314, U. S. National Museum). One $ , from Mt. Tantalus, Oahu,O. H. Swezey (ex spider eggs), from the Bishop Museum collection agreesvery well with the type series from Maui.eEXPLANATION OF FIGUREFig. 1. Titanochaeta swezeyi. a, right wing of male; b, cephalopharyngeal skeleton oflarva; c, anterior spiracle; d, posterior spiracle; and e, dorsal view of puparium.Several empty puparia from which this series was reared, were imbedded in the loose, woolly egg-sack of the spider. From these the following descriptions are offered of the puparium and the cephalopharyngealapparatus of the larva:Puparium (figure 1 e) 3 mm. long; ovoid, subcylindrical; color amberyellow; surface smooth, with sparse rows of minute, conical spinules onsegmental margins. Extreme cephalic end abruptly narrowed and compressed dorsoventrally in a transverse anterior carina about a third aswide as greatest width of puparium. Anterior spiracles borne on antero-lateral angles of this carina, each (figure 1 c) consisting of four sessile,tube-like papillae arising fan-wise in a dorsoventral line. Pupariumevenly rounded caudad; posterior spiracles (figure 1 d) arising slightlyabove dorsoventral midline, bases separated by a distance of a fifth ofgreatest width of puparium, each spiracle in form of a truncated cone,slightly hollowed on inner apex, the spiracular opening apparently in anarc on the inner side before the apex.Cephalopharyngeal skeleton of the larva as in figure 1 b. Mouth hooks(mandibular sclerites) paired, heavily sclerotized, each with a long distalVol. XIV, No. 3, March, 1952 417tooth, a shorter subapical tooth and two subequal, smaller teeth at base.Two pairs of small, bar-like sclerites lying below bases of mandibles andin front of the blunt, heavily sclerotized, anterior arms of the pharyngealplates. Posteriorly the skeleton consisting of a pair of vertical pharyngealplates connected below by a very slender, but heavily sclerotized, transverse band between the anterior arms. (This hypostomal bridge servesto identify these portions of the anterior arms as the hypostomal scleriteswhich in most drosophilid larvae are separate, slender sclerites, but herehave fused with the pharyngeal plates.) Each pharyngeal plate is dividedby a deep posterior cleft into broad dorsal and posterior wings or cornua,the posterior margins of which are gradually less heavily sclerotized. Dorsal wings connected above by a hyaline membrane bearing a small, round,brownish sclerotized, sensory area on the midline in front.Titanochaeta ichneumon Knab differs in its darker, pruinose graythorax, more pubescent eyes, shorter mid fronto-orbitals, dark third an-tennal segment, arista with five rays, single humeral and sternopleuralbristles, scutellum bare except for the four strong marginals, and wingwith only one strong bristle at end of first costal section, the crossveins notinfuscated and much more removed from the wing margin. Male wingwith costal index 2.5, fourth vein index 2.2 and the hind crossvein a thirdas long as penultimate section of fourth vein and 0.39 as long as ultimatesection of fifth vein.Through the courtesy of D. Elmo Hardy and G. E. Pemberton, fourspecimens of ichneumon from Pahala, Hawaii, Feb. 11, 1916, were borrowed from the Hawaiian Sugar Planters' Experiment Station and foundto agree closely with the type lot. The puparia from which they had issuedresemble those of swezeyi, except notably for the shape of the posteriorspiracles. These are in the form of acute, blackened combs with the apicalspiracular openings minute, about two-thirds as far apart as the anteriorpair of spiracles, arising at the sides of a turret-shaped, dorsoposterior,median protuberance, about half as high as its diameter with a distinctbasal constriction or neck, and with its axis at about eighty degrees withthe longitudinal axis of the puparium.Titanochaeta bryani Wirth, new species$, $. Very closely related to swezeyi, differing in the following particulars: Muchsmaller, length about 2 mm., wing 2 mm. Color as in swezeyi, but crossveins of wing notinfuscated. Middle fronto-orbital shorter, half to two-thirds as long as the anterior, anda third to a half as long as the posterior fronto-orbital. Arista with two (in one antenna) or three (in five antennae) rays. Mesonotal setulae in distinct series near mid-line, non-seriate toward sides. Wing more nearly as in ichneumon; female wing withcostal index 2.5; fourth vein index 1.6, due to the anterior crossvein being remarkablyremoved toward base of wing; hind crossvein 0.31 times as long as penultimate sectionof fourth vein and 0.56 times as long as ultimate section of fifth vein. Male wing verysimilar to the female, the respective indices being 2.5, 1.8, 3.3 and 0.5.Holotype $ , allotype, Manoa, Oahu, Hawaiian Islands, O. H. Swezey,collector (ex spider eggs) (in collection of the Experiment Station,H.S.P.A., Honolulu) ; 1 $ paratype, same data (retained for the U. S.National Museum collection). The attached puparia closely resemblethose of swezeyi.

Two new Spider Egg Predators from the Hawaiian Islands (Diptera: Drosophilidae)

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Two new Spider Egg Predators from the Hawaiian Islands (Diptera: Drosophilidae)

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