Somatiosoma Frey, 1958

Ebejer, Martin J., 2009, A revision of Afrotropical Chyromyidae (excluding Gymnochiromyia Hendel) (Diptera: Schizophora), with the recognition of two subfamilies and the description of new genera, African Invertebrates 50 (2), pp. 321-321 : 368-369

Genus Somatiosoma Frey, 1958

Somatiosoma: Frey 1958: 32 .

Type species: Somatiosoma nitescens Frey, 1958: 32 , by original designation.

Frey (1958) initially described Somatiosoma as a subgenus of Chyromya , on the basis of absent presutural dc setae and absent additional marginal setae on the scut, but with setulae on the disc (although Frey describes these as setae, a better description might be fine setulae, since these are the same as those on the scutum, and which Frey refers to as hairs). Frey also drew attention to the fine scutal vestiture.

Diagnosis: Head more or less round with ocp flat or only slightly convex when viewed from above or from side. Disc of ocp entirely or largely bare. Eyes round or almost so and fr about 1/3 width of head and not protruding above antennae, thus not visible in profile. No pra and no post ia setae, only one dc seta; these setae are present separately or together in some other genera. scut with several scattered fine setulae on disc in addition to usual four marginal setae. Short apicoventral seta on mid tibia indistinct and not as long as diameter of tibia at apex. Male postabdomen: ph apd stout and psg highly modified. In female postabdomen, 8 th segment narrow dorsally and membranous; ventral part with two poorly sclerorized plates.

Description:

Head:Yellow, fr not protruding beyond anterior eye margin, sides moderately converging towards antennae, across middle, often with very fine pale setulae; ocp flat to slightly convex when viewed from above, in profile slightly convex and narrowly visible behind eye margin; short setulae on postocular margin and just above ocp foramen, but none on disc of ocp; gena narrow, finely, but distinctly setulose; on lower part, behind with a distinct pale seta directed downwards; vibrissal angle very poorly differentiated; 2 or 3 short vibrissal setulae; face short and depressed, poorly sclerotized, except for a narrow median line, carina never properly developed although this sclerotized median line may give the impression in some specimens that a shallow carina exists; eye round or slightly oval, upper and lower facets of ommatidia almost equal in size; antenna with round third segment, first and second segments short, latter with seta dorsally; arista 3- segmented, usually bare, sometimes very short pubescent; mouthparts small but normally developed, palp short and broad oval to almost round. Chaetotaxy: 3 well-developed orb, anterior inclinate; 1 strong vti and 1 strong vte, oc divergent, pvt distinct and convergent or crossed.

Thorax: Ground colour yellow; scutum with or without slightly darker yellow stripes; mtn and pleura yellow; scutum uniformly covered with short fine setulae. Chaetotaxy: 1–2 pprn, 1 posthu, 0+1 dc, scutal setulae in 8–12 rows between dc lines, with a longer prscut pair, 1 sa and 1 pa, 2 ntpl, ia and pra absent; 1 anepisternal at middle of hind margin and 1 katepisternal at upper posterior corner, sometimes with additional short setae or setulae adjacent to these, prpl absent.

Wing: Hyaline, uniformly microtrichose except for basal half of subcostal cell; costa thinner or broken just distal to weakly sclerotized hu crossvein and broken at R 1; subcosta merges with R 1 just before this reaches costa; veins R 4+5 and M 1+2 parallel to wing margin or very slightly convergent; costa ends just beyond end of vein R 4+5; costal setulae very short and of uniform length, sometimes a few setulae are longer than others at base of wing along anterior edge just before R 1 merges with costa; mixed in randomly amongst the pale costal setulae are darker and thicker setulae appearing as minute spines; 2–8 dark setulae set at intervals along dorsal aspect of costa between R 1 and apex of R

2+3

.

Legs: Yellow and short setulose except front femur where longer posterodorsal and posteroventral setae may be present; mid tibia with short and inconspicuous apicoventral seta; claws black in apical half or more, pulvilli normal.

Abdomen: Predominantly pale yellow in most species; sparse short setulose on all segments; tg sclerotized; st from poorly sclerotized to wholly membranous and very thinly and microscopically setulose.

Male postabdomen: tg 6 distinct from ep, but narrower than tg 5 and ventral margin may be narrowed almost to a point; pregenital st not usually modified; prg always distinct, often highly modified, fused to or articulated with hyp laterally; psg and bac scl both short and difficult to see; ej apd often sclerotized and large; tubule to basiph sometimes visible; distiph large and of complicated structure, partly membranous, but with several sclerotized components; cerc always small, narrowly separated and finely setulose; surs usually separated from ep.

Female postabdomen: Segment 8 with only st sclerotized and this is divided into two lateral plates which, when viewed from below, appear velvety owing to a dense pruinosity; each structure extends medially to form a translucent membranous lobe, which serve to close the genital opening; hypr present, small, membranous or very poorly sclerotized, usually bare or with microtrichia; epiproct not developed; 2 small (0.04– 0.07 mm) s, dark coloured (grey, brown or black), lying deep to lateral aspect of tg 6 or 7; s ducts not sclerotized or pigmented.

Length: ơ and ^body 1.5–2.2 mm, wing 1.5–2.0 mm.

Distribution ( Fig. 68 ): Parts of the Middle East (Arabia, Israel, Oman, Palestine and Yemen) and throughout Africa and many of its islands. It has not been recorded from the Indian subcontinent, but could well occur there.

Ecology: This genus appears to be the most arid-tolerant in the family, and species are more likely to be found in scrub vegetation in eremic zones than species of the other genera. It appears to be the only member of its subfamily to occur in deserts.

Figures

Fig. 68. Distribution of Somatiosoma Frey () and Gymnochiromyia Hendel (•) in Africa.