Hercostomus limosus, Zhang & Yang & Grootaert, 2008

Zhang, Lili, Yang, Ding & Grootaert, Patrick, 2008, Mangrove Hercostomus Sensu Lato (Diptera: Dolichopodidae) Of Singapore, Raffles Bulletin of Zoology 56 (1), pp. 17-28 : 24-25

Hercostomus limosus , new species

( Figs. 20–24 )

Material examined. – Holotype. Male , SINGAPORE: Pulau Ubin, Chek Jawa, 2 Dec.2003, mangrove, Mal. (23097, coll. PG, det. LZ, Si111, ZRC).

Paratypes. SINGAPORE: Pulau Ubin , Chek Jawa, 2 males, 4 females, 2 Dec.2003 ; 1 male, 11 Oct.2005 ; 1 male, 26 Oct.2005; 2

males, 2 females, 22 Dec.2005; 1 male, 1 female, 30 Dec.2005 (sweeping).

Diagnosis. – Wing with wide, yellowish brown to grey stigma behind tip of R 1, stigma reaching the level of thickening of R 4+5. R 4+5 thickened from basal quarter, but narrow again before reaching wing border.

Description. – Male. Body length 3.7 mm, wing length 3.3 mm.

Head metallic green with pale grey pollen. Face wider than first flagellomere, densely grey dusted. Hairs and bristles black. Postocular bristles (including posteroventral hairs) black. Antenna ( Fig. 21 ) yellow, first flagellomere brown, 1.1 times as long as wide, obtuse apically; arista brown, minutely pubescent with very short basal segment. Proboscis brownish yellow with black hairs, palpus brownish yellow with black hairs and black apical bristle.

Thorax metallic green with pale grey pollen. Six strong dc, 7–8 pairs of acr short and hair-like; scutellum with two pairs of bristles (basal pair short and weak). Propleuron with 1 black bristle on lower part. Legs yellow; fore coxa yellow with blackish base, mid and hind coxae black with yellow apex. Fore tarsus from tip of tarsomere 2 onward brownish; mid and hind tarsi from tip of tarsomere 1 onward brownish to brown. Hairs and bristles black. Mid and hind coxae each with 1 exterior bristle. Mid and hind femora each with 1 preapical bristle. Fore tibia with 2 ad and 1 weak pd, apically with 2 bristles; mid tibia with 3 ad, 2 pd and 1 av, apically with 4 bristles; hind tibia with 3 ad, 4 pd and 1 av, apically with 2 bristles. Mid tarsomere 1 with 2 short vs.; hind tarsomere 1 with 1 vs. at base. Hind tarsomere 1 with a black, curved posterior spine at base, directed upwards underneath posterior comb of hind tibia. Relative lengths of tibia and 5 tarsomeres LI 1.5: 0.8: 0.35: 0.25: 0.18: 0.18; LII 2.25: 1.0: 0.65: 0.5: 0.26: 0.24; LIII 2.5: 0.85: 1.05: 0.75: 0.5: 0.32. Wing ( Fig. 20 ) hyaline, with yellowish to brown stigma near end of R 1, The stigma consists of a widening of the tip of R1 and a yellowish to brown colouring of the wing membrane. The stigma is wide, and is narrowly separated from R 2+3 (difference with H. lanceolotus , new species). It extends to the level where the thickening of R4+5 starts. R 4+5 thickened from basal quarter, to a little before ending in costa. R 4+5 and M distinctly parallel apically. M a little thickened at the bulge. CuAx ratio 1.2. Squama yellow with black hairs. Halter white.

Abdomen metallic green with pale grey pollen. Hairs and bristles black. Male genitalia ( Figs. 22–24 ): Epandrium distinctly longer than wide, lateral lobe acute apically; cercus triangular, yellow with brown hairs; hypandrium short and thick, aedeagus with 1 inner large, brown denticle near apex.

Female. Body length 3.6 mm, wing length 3.3 mm. Similar to male, but wing without stigma and R 4+5 not thickened.

Etymology. – The specific name refers to the habitat of G. limosus , new species, being the mudflats in mangrove (Lat. limosus : muddy).

THE RAFFLES BULLETIN OF ZOOLOGY 2008

Distribution. – Singapore.

Remarks. – Hercostomus limosus , new species, and H. lanceolatus , new species, are both similar to H. notatus Becker, 1922 , from Taiwan in having a wing stigma. Examination of a male (Formosa Sauter, Takao 1907.V.3; H. notatus det. Becker), here designated as lectotype revealed that it has R 4+5 thickened from its base onwards and the thickening ends halfway the vein i.e. shortly beyond the stigma. Figure 18 in Becker (1922) does not show this thickening. Further it should be noted that the stigma is not black as Becker wrote, but also brownish like in both other species. Finally the cercus is set with pale hairs, not black ones and the aedeagus does not bear a denticle like in the other two species.

Figures

Figs. 20–24. Hercostomus limosus, new species, male: 20, wing; 21, antenna; 22, male genitalia; 23, cercus; 24, surstyli.

Figs. 14–19. Hercostomus lanceolatus, new species, male: 14, antenna; 15, wing; 16, male genitalia; 17, claw-like appendage on aedeagus; 18, ventral lobe of surstyli; 19, dorsal lobe of surstyli.