Melastrongygaster Shima

Shima, Hiroshi, 2015, Melastrongygaster, a new genus of the tribe Strongygastrini (Diptera: Tachinidae), with five new species from Asia, Zootaxa 3904 (3), pp. 427-445 : 428-429

Melastrongygaster Shima , gen. nov.

Type species: Melastrongygaster atrata Shima , sp. nov., by present designation.

Etymology. The genus name is formed from the Greek prefix melas (= black) added to the tachind generic name, Strongygaster , meaning black Strongygaster .

Diagnosis. Medium to small-sized black tachinid flies; male almost holoptic, female dichoptic eye bare. Head rather round-triangular, frons weakly curved; face less than 1/2 length of frons; antenna short, arista bare, thickened at most on basal 1/4, 2nd aristomere shorter than wide; gena wide and genal dilation occupying most of gena, with dense long black hairs; occiput with only black hairs. Thorax mostly black, at most with thin grayish pruinosity on postpronotal lobe and presutural area of scutum; prosternum bare; 3 postpronotal setae, middle seta slightly set forward; 2 postsutural intra-alar setae widely separated; 3 strong marginal scutellar setae, apical setae strong and crossed; wing cell r4+5 open. Abdomen with strong median discal and marginal setae, sternites well exposed.

Description. Male & female. Head almost holoptic in male, frons strongly narrowed above and frontal vitta obliterated to a narrow line in front of ocellar triangle, dichoptic in female, vertex about 1/4 of head width, frontal vitta at most weakly narrowed above; frons 1.5–2 times as long as face in profile; lunule bare; parafacial bare; face weakly concave, very weakly carinate on upper median 1/2, lower margin flat or at most weakly warped forward, not extending beyond vibrissal angle; vibrissa nearly level with lower margin of eye, 1.5–2 times as long as antenna; gena wide, genal dilation occupying most of gena, with dense long black hairs; occiput with only black hairs; antenna short, 1st flagellomere at most 1.5 times as long as pedicel, base of antenna below level with middle of eye height, arista bare, 1st and 2nd aristomeres very short, 3rd aristomere thickened on at most basal 1/4; prementum shorter than antenna; labella large; palpus well developed, weakly clavate, longer than prementum. Prosternum bare; proepisternum bare, proepisternal seta strong; postpronotal lobe usually with 3 setae, middle seta more or less set forwards from others; 1 or 2 presutural and 3 postsutural acrostichal setae; 2 or 3 presutural and 3 postsutural dorsocentral setae; 2 postsutural intra-alar setae, distance between these setae greater than that between transverse suture and anterior seta; 3 supra-alar setae, anterior seta nearly as long as, or slightly shorter than, anterior intra-alar seta and distinctly longer than notopleural setae; anepimeral seta developed, extending backward beyond posterior margin of upper calypter; 2–3 katepisternal setae; katepimeron bare; anatergite with minute hairs; 3 pairs of strong marginal scutellar setae, subapical setae strongly divergent and apical setae crossed and suberect; metathoracic spiracle small and rather sparsely haired on both sides. Wing with costa setulose ventrally on 1st, 2nd and 3rd costal sectors, bare dorsally, costal spine absent; wing veins bare except basal node of vein R4+5 which bears 0–3 fine setulae; cell r4+5 open; vein M obtusely curved; vein CuA1 not reaching wing margin. Legs stout; hind coxa bare posterodorsally; fore tibia with 2–3 preapical dorsal setae, anterodorsal seta strong, if 3 setae, then posterodorsal seta fine; hind tibia with 3 preapical dorsal setae and well developed apical posteroventral seta. Abdomen long ovate; syntergite 1+2 excavated to basal 1/3–1/4 dorsally; discal setae present on 3rd to 5th tergites; sternites well exposed and densely haired.

Male terminalia: Fifth sternite nearly rectangular, posterior margin weakly concave; 6th tergite entire, nearly as long as and free from syntergosternite 7+8; 6th sternite short, nearly symmetrical; syntergosternite 7+8 connected to epandrium with narrow membrane; epandrium with narrow anterior ventral corner, 2 or 4 pairs of very strong setae present in addition to normal hairing; surstylus broad triangular in dorsal view and narrow and elongate in lateral view, inner basal wall extending anteroventrally; bacilliform sclerite indistinct or very short and fused posteriorly with inner wall of surstylus; hypandrium broadly expanded posteriorly on both sides, hypandrial arms narrowly separated dorsally; pregonite absent; postgonite short and broad; phallus very short, no differentiation between basiphallus and distiphallus, broadly membranous on dorsal and lateral portions; ejaculatory apodeme small or only narrowly sclerotized; phallic guide (intermedium) undeveloped; cerci in dorsal view close together on median portion, apically varied from parallel to divergent.

Remarks. Tschorsnig (1985), in discussing the characteristics of the male terminalia of the Tachinidae , gave 12 character states as peculiar to the Strongygastrini . These included the 5th abdominal sternite only weakly excavated on posterior margin, 6th sternite short and nearly symmetrical, bacilliform sclerite fused posteriorly with inner wall of surstylus, only one pair of the gonites recognizable and phallus very short and consisting two partly membranous distal rings. Melastrongygaster shares many of these character states except the 6th abdominal tergite is separated from the syntergosternite 7+8, surstylus is well developed and separated from the epandrium and ejaculatory apodeme is rather well sclerotized. These states are in contrast to Tschorsnig’s characterization of the tribe in which the 6th tergite is continuous with syntergosternite 7+8, surstylus is short and fused with the epandrium, and ejaculatory apodeme is indistinct. In other external features Melastrongygaster differs from other members of the tribe in its bristly black body, wholly black hairs on the occiput, three pairs of long and strong marginal scutellar setae and wing cell r4+5 open.

In the key to genera of the Palearctic Tachinidae ( Tschorsnig & Richter, 1998) this genus will key to Pelamera Herting, 1969 , which is, however, a very different genus. Melastrongygaster differs from Pelamera in the parafacial and gena narrower, the latter mostly occupied by a densely long-haired genal dilation, arista thickened only on basal 1/4 and second costal sector of the wing haired below and anatergite haired.