Syntormon singaporensis, Grootaert, Patrick, Yang, Ding & Wang, Mengqing, 2006

Grootaert, Patrick, Yang, Ding & Wang, Mengqing, 2006, First record of Syntormon from Singapore with the description of a new species (Insecta, Diptera, Dolichopodidae), Zootaxa 1114, pp. 53-59 : 55-58

Syntormon singaporensis sp. nov.

( Figs. 1–5 )

Material examined: Holotype male: SINGAPORE, Sime forest, 8 April 2005, stream near tree top walk, alt. 50m (25053, leg. P. Grootaert, Si 701 in ZRC).

Paratypes: 10 males, 2 females with same provenance as holotype (1 male in CAU, 1 male RBINS, 8 males from the same provenance have been extracted for DNA sequencing); 2 males, Sime forest, 14 March 2005, Mal. 2 (25013, leg. P. Grootaert, Si423); 3 males, 6 May 2005 (25128, Si1066); 1 male, 3 June 2005 (25135, Si1073); 1 male, 22 July 2005 (25271, Si1075); 1 male, 12 August 2005 (25294, Si1057); 1 male, 19 August 2005 (25300, Si1058); 1 male, 16 September 2005 (25353, Si1068); 3 males, 23 September 2005 (25364, Si1071).

Diagnosis. Third antennal segment 2.8 times longer than wide in male; arista a little longer than third segment. Basal antennal segment black; third segment brown. 6 strong dc, uniseriate acr (about 20). Legs yellow, but mid and hind coxae black (except narrow yellow apex). Hind tarsomeres 1 and 2 simple; hind tarsus with apical 4 tarsomeres brown. Abdomen metallic green, but with second and third tergites largely yellow (base with metallic green stripe); following tergites sometimes with a small yellow patch at each side.

Description.

Male. Body length 3.64 mm, wing length 3.78 mm.

Head metallic green. Hairs and bristles on head black, but lower postocular bristles (including ventral hairs) pale. Face very narrow, almost touching near middle. Ocellar tubercle with 2 strong ocellars and 2 posterior hairs. Antenna with basal segments black. First antennal segment (scape) with a strong interior tooth­like projection ( Figs 1–2 ). Third antennal segment (first flagellomere) brown, ventrally a little paler; 2.8 times longer than wide, ventrally with an angular bent ( Fig. 1 ); arista black, a little longer than third antennal segment, or nearly as long as three antennal segments together, shortly pubescent. Proboscis dark brown with black hairs; palpus brown with short black hairs.

Thorax metallic green. Hairs and bristles on thorax black; 6 strong dc, about 20 uniseriate acr. 1 long and 1 short humeral hairs, 1 long ph, 1 short ih, 1 short su, 1 long anterior and 1 slightly short posterior npl, 1 slightly short anterior and 1 long posterior sa, 1 long psa; scutellum with 1 pair of long marginals. Propleuron with several pale hairs on upper and lower portions.

Legs yellow; fore coxa yellow including extreme base, mid and hind coxae (except narrow apex) blackish­brown; hind tarsus with apical 4 segments brown due to the dense setting of black hairs, ground­colour yellowish. Hairs and bristles on legs black; fore coxa on basal half with pale, fine hairs anteriorly and on apical half the hairs are black; tip with 5 long black bristles; mid coxa with short pale hairs at base, further black haired; hind coxa with 1 strong exterior bristle at basal 2/5 and a short black hair beneath. Fore femur narrow without conspicuous bristles. Mid femur with a preapical 1 av and pv. Hind femur with only a preapical av, posteroventrally at most a weak hair. Fore tibia with 2 dorsal bristles and a serration in apical half. Mid tibia with 3 ad and 1 pd, apically with 4 bristles; hind tibia with 3 weak ventrals, 2 ad, 3–4 pd. Fore tarsomere 1 nearly as long as tarsomeres 2– 5; hind tarsomere 1 shorter than tarsomere 2. Relative lengths of femur, tibia and 5 tarsomeres: LI: 0.98: 0.94: 0.7: 0.3: 0.24: 0.14: 0.11; LII: 1.33: 1.40: 0.7: 0.38: 0.21: 0.17: 0.14; LIII: 1.54: 1.6: 0.24: 0.52: 0.36: 0.24: 0.11.

Wing brownish tinged; veins dark brown. R4+5 and M weakly convergent apically; Wing boss at about basal third of apical section of M. Tp nearly as long as apical section of Cu. Squama yellow with 6 long pale hairs. Halter white.

Abdomen mainly metallic green, but with a yellow pattern. First tergite divided into two transverse sections. The basal section, consisting of two narrow triangular plates; posterior band a single plate, metallic green, bearing the usual long marginal bristles. Tergite 2 almost completely yellow except for a very narrow, dark basal stripe. Tergite 3 also almost completely yellow, but with a broader dark basal border. Tergites 4 and 5 almost completely metallic green, but with a small yellow triangular spot at both sides. Sternites yellow except for the metallic green sternite 5.

Hairs and bristles on abdomen black, segment 1 with a few long pale hairs at sides. Male genitalia ( Figs. 4–5 ). Dorsal surstylus with 2 strong dorsal bristles. Ventral surstylus with a very long bristle ventrally near base and a strong lateral bristle. No epandrial bristles. Hypandrium broad.

Female. Body length: 3.92–4 mm, wing length: 3.5–3.92 mm.

Identical to male in most characteristics. Face wide, about as wide as third antennal segment is long, bulging below. Upper part of face concave. Third antennal segment much shorter than in male, about as long as deep (1.8 times as long as high); arista nearly 2 times as long as third antennal segment. Apical part of third segment triangular and much shorter than in male ( Fig. 3 ). Although there is a difference in length of the third antennal segment, total length of the antenna is identical in both sexes. Abdomen with the same yellow pattern as in male, but in female also tergite 4 with an apical yellow band, and not limited to a triangular spot on the side as in male.

Etymology. The name refers to the type locality, Singapore.

Comments. S. singaporensis resembles S. triseta Yang, 1998 from Fujian ( China) in that the hind tarsomere 1 is simple in structure (no basal ventral projection), hind tibia and tarsi are not flattened, fore coxae are yellow and posterior four coxae are brownish black, third antennal segment is less than 3.5 times as long as high (but 2.8 times), arista is nearly as long as third segment and the acrostichals are uniseriate. S. singaporensis differs from S. triseta in that the latter has three ventral bristles on the hind tarsomere 1 and has a completely metallic green abdomen. S. singaporensis has only a single, weak ventral bristle on the hind tarsomere 1 and at least the tergites 2 and 3 are broadly yellow.

S. flexibilis Becker, 1922 , a widely distributed species that we have seen during the present study ( China, Qinhuangdao, 4 October 2005) has also the basal abdominal segments yellow, but the hind tarsomere 1 is swollen at its base and bent ventrally. Hind tarsomere 2 bears an apical protuberance. In S. singaporensis hind tarsomeres 1 and 2 are simple.

Bionomics. The habitat of S. singaporensis seems to be the muddy and sandy riverbanks of permanent streams in rain forest. Daily, the riverbanks were temporarily exposed to the sun. This type of habitat was quite stable and permanent during the year, even during the dry season. S. singaporensis is likely present throughout the year since we observed it regularly from March till October. Only a single population of S. singaporensis was found in Singapore up to now, and this despite intensive sampling in various similar habitats nearby. Perhaps these habitats were not permanent enough since they suffered from drought during the dry season.

The record of Syntormon here in Singapore is remarkable since it is the first record from low altitude in rain forest near the equator. Future records in Southeast Asia will show if we also deal here with a relic from dry spells during the glaciations ( Daugeron & Grootaert, 2004).

Figures

FIGURES 1 – 3. Syntormon singaporensis sp. nov. 1. Male antenna, exterior view; 2. male, base of antenna, interior view; 3. female antenna.

FIGURES 4 – 5. Syntormon singaporensis sp. nov. male paratype. 4. Hypopygium ventral view; 5. hypopygium lateral view.