Mikrostyles Jaschhof

Jaschhof, Mathias, 2016, A review of world Diallactiini (Diptera, Cecidomyiidae, Winnertziinae), with the description of six new genera and seventeen new species, Zootaxa 4127 (2), pp. 201-244 : 235

Genus Mikrostyles Jaschhof gen. nov.

Type species, latolobata sp. nov., here designated.

The genus Mikrostyles is introduced here for several small, mostly pale yellow Diallactiini with long eye bridge, the Haplusia type of venation ( Fig. 18E ), and distinctive male genitalia. Of four different species at my disposal, all from Brunei, two are described and named here.

Diagnosis. The gonostylar body is markedly reduced in size, while the apical tooth is rather large compared to the body ( Figs 18A , 19 ); the shape of both the body and tooth are specific to a species. The gonostylus is almost entirely enveloped by the gonocoxa, which is elongated posteriorly into a large lobe ( Figs 18A , 19 ); the outline of these lobes is also species-specific. Females of Mikrostyles are unknown.

Other male characters. Body length 1.8–2.0 mm. Head. Postgenal setae 5–10, clustered. Eye bridge 8–10 ommatidia long dorsally, covering all vertex. Scape and pedicel concolorous with flagellum, scape with 1–2 setae, pedicel usually unsetose, exceptionally with 1 seta. Flagellomeres 14. Neck of fourth flagellomere longer than node; node with short setae basally, in between occasionally 1 or 2 short hair-like translucent sensilla, a crenulate whorl with long sensory hairs with hooded alveoli medially, more such sensory hairs scattered distally, especially ventrally, numerous short hair-like translucent sensilla distally, microtrichia only basally. Clypeus unsetose. Palpus slightly longer to slightly shorter than head height, 4 segments, translucent sensilla on two, rarely three proximal segments, simply hair-shaped or two-branched, fourth segment longest. Thorax. Scutellum brown; scutum partly light brown; anepisternum light brown. Scutal and scutellar setae sparse. Wing length / width 2.5–2.7. Membrane completely covered with setae. Costal break distinct; btv setose; both M1+2 and M4 absent; CuA extending to wing margin. Legs with narrow scales in addition to setae. Coxae slightly darker than other segments, tarsi slightly lighter. Basitarsi without spine. Claws slightly bent, untoothed. Empodia vestigial. Genitalia. Ninth tergite subtrapezoid, setose. Gonocoxae massive; ventral bridge fully membranous, a posterior outgrowth of that membrane (not illustrated) occupying much of the ventral emargination; medial bridges with dense cover of microtrichia intermingled with fine setae; apodemes merged anteriorly to form a long plate with protruding corners basally and broadly rounded processes apically. Gonostylus with a very few setae. Ejaculatory apodeme long, moderately sclerotized. Tegmen weakly sclerotized, elongate, constricted medially, apex broadly rounded, bent dorsally; apodemes narrow, directed ventrolaterally.

Etymology. Mikrostyles is a Greek word meaning “with small gonostyli”. Gender of this name is feminine.

Discussion. The geographical distribution of Mikrostyles , the only diallactiines with miniaturized gonostyli, is to present knowledge confined to Brunei. All the four species identified were collected at one and the same site, and at one time, so one may assume that many more species occur elsewhere. Species are extremely similar to each other, differing mainly in details of the male genitalia. The association of tiny gonostyli and large posterior gonocoxal lobes as described here for Mikrostyles occurs here and there in other Cecidomyiidae , such as in the Palearctic Lestremia parvostylia ( Jaschhof 1994: fig. 1a) (in Lestremiinae ) and in an unnamed genus of Micromyini (in Micromyinae ) from Malaysia (Jaschhof, unpubl.), and even in other Sciaroidea, such as the mycetophilid genus Manota Williston, 1896 ( Jaschhof & Hippa 2005: figs 9–25). Mikrostyles and Bruneiplusia , also from Brunei, appear to be closely related. The two genera are practically indistinguishable with respect to nongenitalic characters, whereas male genitalic structures are fundamentally different, with the exception of the gonostyli that in both genera are inserted ventrally, not posteriorly, on the gonocoxae. This condition is without doubt derived and here regarded as a synapomorphy of Mikrostyles + Bruneiplusia .

Figures

FIGURE 19. Male genitalia of Mikrostyles latolobata (holotype male). Scale 0.05 mm.

FIGURE 18 A – E. Mikrostyles angustilobata (holotype male). A: Genitalia, ventral. B: Outline of genitalia, ventral. C: Palpus and labella, lateral. D: Fourth flagellomere, lateral. E: Wing. Scales for A – D, 0.05, for E, 0.5 mm.