Chersodromia singaporensis, Shamshev, Igor & Grootaert, Patrick, 2005

Shamshev, Igor & Grootaert, Patrick, 2005, Two new species of the genus Chersodromia Walker (Diptera: Hybotidae) from Southeast Asia, Zootaxa 942, pp. 1-10 : 6-9

Chersodromia singaporensis new species

Fig. 2

Diagnosis. A small species with 1 pair of vertical bristles, broad face, brown basal antennal segments, postpedicel having long dorsoapical extension, brownish palpus, katepisternum largely shining, brownish yellow legs, pale halteres and finely infuscate wings.

Description. Male. Body length 1.5 mm, wing length 1.5 mm. Head black in groundcolour, with black bristles. Frons greyish pollinose, rather narrow, widened towards ocellar tubercle, in middle nearly 1.5 times as broad as anterior ocellus. Face almost linear, somewhat widened in lower part, in middle as wide as frons. Ocellar tubercle with 2 pairs of long bristles. Vertex with 1 pair of long bristles. Occiput finely greyish pollinose, with some scattered setulae longer in lower part. Antennae ( Fig. 2 A) with scape and pedicel brown, postpedicel and style paler, yellowish­brown. Postpedicel with long dorsoapical extension, nearly 2 times longer than wide, style about 3.0 times longer than postpedicel. Genae rather narrow. Palpus brownish, moderately large, elongate oval, with several short bristles and 1 longer bristle at apex; sensory pit present.

Thorax black in ground­colour, greyish pollinose, with black bristles; katepisternum largely shining. Postpronotal bristle long, inclinate. Mesonotal bristles well prominent, including 1 long inclinate presutural supra­alar, 2 notopleurals, 1 rather short postsutural supra­alar, 1 postalar and 4 (inner ones cruciate) scutellars. Acrostichals biserial, equally short, about 8 per row, extending to base of scutellum, well separated from dorsocentrals. The latter uniserial, long, about 6 per row, extending to base of scutellum, some setulae present on supra­alar space.

Legs brownish yellow, tarsi somewhat paler. Femora subequal in thickness. Fore tibia rather spindle­like, narrowed at base. Coxae and trochanters with ordinary setation. Fore femur with 1 row of antero­ and 1 row of posteroventral moderately long bristles, bearing 1 short anterior subapical bristle and some bristles round tip. Fore tibia bearing 1 long anteroventral and 1 similar posteroventral bristle in subapical part and with 1 shorter posteroventral bristle near middle. Fore tarsus somewhat dilated, nearly as long as fore tibia, tarsomere 1 with 1 long posteroventral bristle. Mid femur with 1 row of posteroventral, moderately long (becoming shorter toward apex of femur) and 1 row of shorter anteroventral bristles, 1 long bristle at extreme base and 1 anterior subapical bristle. Mid tibia with 1 row of anteroventral spinules, 2 long anterodorsal and 2 similar posteroventral bristles in middle part and circlet of 3 subapical bristles. Mid tarsus somewhat dilated, nearly as long as mid tibia. Hind femur with 1 row of short (2 subapicals longer) posteroventral bristles, 1 row of short posterodorsal bristles and some prominent dorsal bristles near base. Hind tibia with 2 long anterodorsal, 3 similar dorsal and 2 anteroventral bristles, bearing 2 shorter subapical bristles anteriorly and longer ventral setulae. Hind tarsus slender. Otherwise legs clothed in ordinary setulae.

Wing normally developed, finely infuscate, covered with uniform microtrichia. Costal vein with short setulae along anterior margin. One long basicostal bristle present. Vein R1 meeting costa at middle of wing. Veins R4+5 and M1+2 parallel and straight in apical part. Vein A1 absent. Halter yellow. Squamae yellow, with scattered yellow fringes.

Abdominal sclerites mostly pale brown and with scattered dark setulae, pregenital segments darker and longer bristles. Intersegmental gland­like structures or squamiform setae absent.

Hypopygium ( Fig. 2 B) rather large, black. Hypandrium with 6 long bristles in apical part. Epandrium completely divided. Left epandrial lamella small, fused to hypandrium, with several short bristles in apical part. Left surstylus ( Fig. 2 C) consisting of two entirely separated sclerites; upper sclerite rounded, with small additional process at base; lower sclerite digitiform in apical part. Right epandrial lamella subtriangular ( Fig. 2 D), clothed in numerous bristles, bearing 3 spine­like bristles on inner side at apex and 2 similar bristles (1 bristle longer and stronger) on dorsal margin in apical part. Right surstylus not prominent. Both cerci unbranched, bearing several long bristles, lacking spines, short, subequal in length. Hypoproct unmodified. Phallus short.

Female. Body length 1.6–1.7 mm, wing length 1.5–1.6 mm. Mid tibia with less prominent ventral spinules. Cerci brown. Otherwise as in male.

Derivatio nominis. The name refers to the country.

Distribution. Singapore.

HOLOTYPE. Male. SINGAPORE, Pulau Ubin, Chek Jawa, 11.XII.2002, mangrove (sample 22061, leg. P. Grootaert; conserved in alc., RBINS).

PARATYPES. 2 females, same provenance as holotype, but sample 22059, leg. P. Grootaert; 1 male, 2 females, Singapore, Pulau Ubin, Noordin beach, 11.XII.2003, white sand beach, in the burrows of Ghost crabs (sample 22062, leg. P. Grootaert; in coll. Raffles Museum); 4 males, 2 females, MALAYSIA, Sedili kecil, 12.X.2000, sandy beach (sample 20046, leg. P. Grootaert; in alc.coll. RBINS).

Bionomics. Chersodromia singaporensis sp. nov. was only found on white sandy beaches or in mangroves with at least sandy patches. On one beach, specimens were found in the burrows of Ghost crabs, Ocypoda sp.

Remarks. The new species fits quite well within the definition of the C. speculifera group sensu Chvála (1977). Among the Palaearctic species belonging to this group C. singaporensis sp. nov. resembles C. flavipes Chvála , known from the Atlantic coast of Spain. However, there are three species described from Papua New Guinea ( Grootaert, 1992), which actually are more closely related to the new species sharing a single pair of vertical bristles, postpedicel with a distinct dorsoapical extension and a very similar structure of the male terminalia. All these species differ from C. singaporensis sp. nov. by pale yellowish ( C. flavipyga Grootaert ) or yellowish­white ( C. micra Grootaert ) to pale whitish ( C. nigripyga Grootaert ) palpus and by the lack of a presutural supra­alar (= posthumeral) bristle.

Figures

FIGURE 2. Male Chersodromia singaporensis sp. n., A, lateral view of antenna; B, ventral view of hypopygium; C, right lateral view of left surstylus; D, left lateral view of right epandrial lamella. Scale 0.1 mm.