Xenosciara, Vilkamaa, Pekka & Hippa, Heikki, 2004

Vilkamaa, Pekka & Hippa, Heikki, 2004, The genus Xenosciara gen. n. and the phylogeny of the Sciaridae (Diptera), Zootaxa 699, pp. 1-24 : 10-14

The genus Xenosciara gen. n.

Type­species Xenosciara invisa sp. n.

Characters

Medium­sized Sciaridae , wing length 3.2 mm.

Head ( Fig. 6 ). Eye bridge present, 4 facets wide. Eyes without interfacetal microtrichia, with interfacetal setae which extend well beyond the curvature of the facets. Ocelli three, in an equilateral triangle. Anterior vertex short, setose. Prefrons setose, the setae unequal in size. Clypeus distinctly separated from prefrons, setose. Antennal scape and pedicel ( Fig. 6 A) subglobular, with several ventral setae, flagellum with 14 flagellomeres which are subequal in size, the body about two and a half times as long as wide, the neck short, about one­third the width of the body, the vestiture of the flagellomeral body ( Fig. 6 C) with long seta­like sensillae arising from weak plate­like depressions, with a few short seta­like sensillae, without socketed setae, without hyaline sensillae, the ultimate flagellomere ( Fig. 6 D) apically with two sharp pegs, microtrichia present only basally on flagellomere 1. Maxillary palp with palpifer and three palpomeres; galea long, about as long as palpomere 1, apically branched; palpomere 1 unusually long, about four times as long as broad, palpomere 2 one­third of the length of palpomere 1, palpomere 3 about the length of palpomere 2, only slightly constricted basally; palpifer non­setose, palpomere 1 with one large lateral seta and several weaker dorsal setae, with scattered hyaline sensillae dorsally, palpomeres 2–3 with numerous setae, all with blunt apex.

Thorax ( Fig. 7 ). Dark brown, setae dark. Scutum broadly setose laterally, with shorter and longer setae, dorsocentral setae in three rows, with longer and shorter setae, acrostichal setae in one row which is present only on the anterior half. Scutellum with numerous setae of unequal length, with a few long curved setae posteromedially. Anterior pronotum with a few setae, posterior pronotum non­setose, episternum 1 setose. Anepisternum with a deep v­shaped cleft dorsally, non­setose. Anepimeron with the anterior margin interrupted by the pleural pit, the posteroventral process reaching metepisternum and posteroventral margin of katepisternum, not shortened, the anterior margin ending ventrally at anterodorsal corner of episternum 3, non­setose. Katepisternum high, the dorsal margin slightly curved, not angulated, non­setose. Pleural pit at the middle of the dorsal margin of katepisternum. Laterotergite with anterior margin strongly sigmoid, non­setose. Metepisternum non­setose. Metanotum non­setose, phragma intruding into the base of abdomen.

Wing ( Fig.8 ). Hyaline, tinged with brown. R1 slightly shorter than R. r­m unusually long. stCu present, C, R, R1, R5 setose, other veins dorsally non­setose, all except C ventrally non­setose; wing membrane non­setose, the setae on posterior wing margin only on dorsal side. Haltere as long as coxae, the knob with a dorsal stripe of setae.

Legs ( Fig. 8 ). Unicolorous, slightly paler brown than thorax; slender. Coxae long, several times as long as broad, metacoxa slightly shorter than the others. Tibiae with both socketed setae and non­socketed setae (enlarged microtrichia), both subequal in size, middle and hind tibia with a few enlarged dorsal and lateral setae, on front tibia only apically, front tibia prolaterally with a subapical patch of setae, hind tibia with a retrolateral subapical transverse row of strong setae, without a dorsal row of strong setae. Tibial spurs 1+2+2, all subequal in size, longer than the apical width of tibia. Tarsomeres short, basitarsomere less than half the length of tibia, the two basal tarsomeres with enlarged setae ventrally/lateroventrally, tarsomeres 3 and 4 only apically; tarsal claws simple, pulvilli and empodium branched.

Abdomen ( Fig. 8 ). Brown. Tergites 2–7 with one pair of plaques. Male sternum 9 united with hypopygium. Hypopygium ( Fig. 9 ). Tergite 9 large, apically rather evenly curved. Gonocoxites ventrally completely fused, gonocoxal apodemes short, weakly sclerotized, ending far posterior from the anterior margin of hypopygium, the apodemes of both sides medially united only by membrane. Gonostylus flexible in vertical plane, without apical tooth, with two apical megasetae, without flagellate setae, with the basomesial structures simple, with the basolateral apophysis strong, basoventral in position. Parameres weak, united to form a tegmen, parameral apodemes transverse, free from gonocoxal apodemes. Aedeagus without teeth or microtrichia, aedeagal apodeme/genital rod absent; a setose membrane extending from the ventral apicomesial part of gonocoxites to aedeagus. Tergite 10 membraneous, bilobed, with several short setae. Cercus flattened, setose only on posterior margin.

Female characters unknown.

Diagnostic characters

Xenosciara differs from all known Sciarinae by each of the following characters: 1) the very long palpomere 1, 2) ventrally fused male gonocoxites, 3) gonostyli movable in a vertical direction, 4) vertical tegmen, 5) setae only on the margin of the cercus, and 6) a setose membrane from the fused ventral part of the gonocoxites covering the aedeagus.

In its habitus, Xenosciara is a normal, unspecialized member of the Sciaridae . With its long maxillary palp, Xenosciara resembles Dolichosciara Tuomikoski , Prosciara Frey , and Keilbachia Mohrig , but in these groups palpomere 3 is elongated and distinctly longer than the other palpomeres, and only Xenosciara has palpomere 1 strongly elongated. The basoventrally fused gonocoxites is not a rare character in the Sciaridae and the fused basal part can take up to half the length of the coxites in some groups ( Claustropyga Hippa, Vilkamaa & Mohrig ), but there are no other taxa in which the ventral aspect of hypopygium resembles that of Xenosciara . A reminiscent structural type is found in several other Sciaroidea, however. The gonostyli that work in a vertical direction are quite exceptional in the Sciaridae , but occur in some taxa of the other Sciaroidea (e.g. Heterotricha Loew, Rhynchoheterotricha Freeman and a few groups of the Cecidomyiidae ). The type of association of the gonocoxites and the aedeagus/tegmen complex does not resemble that of any other Sciarinae but is reminiscent of Sciarotricha in terms of the membranous connection between the aedeagus and gonocoxites. Sciarotricha , however, has separate parameres and the membrane is only microtrichose.

Figures

FIGURE 6. Xenosciara invisa sp. n. (holotype). — A: Head, frontal view, — B: Maxillary palp, basal palpomeres, dorsal view, apical palpomere, mesioventral view, — C: antennal flagellomere 4, ventral view, — D: apex of flagellomere 14, ventral view. Scale for A 0.50 mm, for B and C 0.10 mm, for D 0.05 mm.

FIGURE 7. Xenosciara invisa sp. n. (holotype): Thorax, lateral view. Scale 0.50 mm. 1 = scutum, 2 = scutellum, 3 = metanotum (phragma), 4 = anterior pronotum, 5 = episternum 1, 6 = anterior anepisternum, 7 = anterior anepimeron, 8 = pleurotergite, 9 = katepisternum, 10 = pleural pit, 11 = episternum 3, 12 = halter, 13 = coxa 2, 14 = anterior spiracle, 15 = posterior spiracle.

FIGURE 8. Xenosciara invisa sp. n. (holotype). — A: Apical part of front tibia, prolateral view, — B: Apical part of hind tibia, retrolateral view, — C: Wing, dorsal view, — D: Abdominal segment 5, lateral view. Scale for A, B and D 0.20 mm, for C 2.0 mm. 1 = tergite, 2 = sternite, 3 = spiracle, 4 = plaque.

FIGURE 9. Xenosciara invisa sp. n. (holotype). — A: Hypopygium, lateral view, — B: Hypopygium, dorsal view, — C: Hypopygium, ventral view, — D: Hypopygium, posterior view. Scale 0.20 mm. 1 = gonocoxite, 2 = gonostylus, 3 = basolateral apophysis of gonostylus, 4 = apical megasetae of gonostylus, 5 = tergite 9, 6 = cercus, 7 = tegmen, 8 = apodeme of tegmen (parameral apodeme), 9 = sternite 10, 10 = apicodorsal flagellate seta of gonocoxite.