Simulium (Gomphostilbia) tahanense Takaoka & Davies, 1995

Takaoka, Hiroyuki, Ya’Cob, Zubaidah & Sofian-Azirun, Mohd, 2018, Classification, annotated list and keys for the black flies (Diptera: Simuliidae) of Peninsular Malaysia, Zootaxa 4498 (1), pp. 1-65 : 16-18

16. Simulium (Gomphostilbia) tahanense Takaoka & Davies, 1995

Simulium (Gomphostilbia) tahanense Takaoka & Davies, 1995: 24 –28 (Female, pupa and larva).

This species was described from females, pupae and larvae (Takaoka and Davies, 1995). It is characterized in the female by the elongate labrum 1.2 times the length of the clypeus, frons widely bare except several hairs along both lateral margins, and claw with a medium-long tooth, in the male by the elongate labrum 0.93 times the length of the clypeus, in the pupa by the gill with eight slender filaments arranged as [1+1+(1+2)]+2 from dorsal to ventral, of which two ventral paired filaments are about twice the length of the other six filaments, and in the larva by the body grayish yellow with two grayish black annular bands (one on thoracic segment 1 and the other on abdominal segment 1) and grayish black areas on abdominal segments 5–8.

This species is sporadically distributed in lowlands of Peninsular Malaysia. It was also recorded from Sarawak (Takaoka, 2012) and Kalimantan, Indonesia (Takaoka et al., 2017b).

The male of this species is described for the first time.

Male. Body length 2.2 mm. Head. Slightly wider than thorax. Upper eye consisting of 11 vertical columns and 11 horizontal rows of large facets on each side. Clypeus brownish black, thinly gray pruinose, shiny when illuminated at certain angles, moderately covered with yellow short hairs interspersed with few yellow longer hairs near lower margin. Antenna composed of scape, pedicel and nine flagellomeres, dark brown except scape, pedicel and base of first flagellomere yellow and rest of first flagellomere medium brown; first flagellomere elongate, 1.9 times as long as second one. Labrum elongate, 0.93 times as long as clypeus. Maxillary palp with five segments, light brown, proportional lengths of third, fourth, and fifth segments 1.0:0.9:1.8; third segment ( Fig. 2A ) somewhat widened apically; sensory vesicle ( Fig. 2A ) ellipsoidal, small, 0.18–0.21 times as long as third segment, and with small opening. Thorax. brownish black to black, thinly gray pruinose and shiny except median nonpruinose vitta which is extended from anterior margin to middle, little less than one-third of width of scutum, parallel-sided anteriorly, and pointed posteriorly; scutum moderately covered with medium to dark brown short hairs. Scutellum black, with dark brown medium-long to long upright long hairs. Postnotum black and bare. Pleural membrane bare. Katepisternum brownish black to black, shiny, moderately covered with dark brown short hairs. Legs. Foreleg: coxa and trochanter yellow; femur dark yellow; tibia dark yellow to light brown except apical one-fourth medium brown; tarsus brownish black, with moderate dorsal hair crest; basitarsus somewhat dilated, 5.4 times as long as its greatest width. Midleg: coxa dark brown; trochanter yellow; femur dark yellow except apical cap light brown; tibia light brown; tarsus light brown except basal four-fifths of basitarsus and base of second tarsomere dark yellow. Hind leg: coxa dark brown; trochanter yellow; femur dark yellow except base yellow and apical cap medium brown; tibia medium to dark brown except basal tip dark yellow, and median large portion of outer surface light brown; tarsus ( Fig. 2B ) medium brown except little less than basal four-fifths of basitarsus (though base light brown) and basal half of second tarsomere yellow; basitarsus ( Fig. 2B ) narrow, slightly widened from base to basal one-fifth, slightly tapered to middle, then nearly parallel-sided, 5.42 times as long as wide, and 0.55 and 0.56 times as wide as greatest width of tibia and femur, respectively; calcipala ( Fig. 2B ) well developed, slightly longer than wide, and 0.41 times as wide as greatest width of basitarsus; pedisulcus ( Fig. 2B ) well developed. Wing. Length 1.5 mm. Costa with dark brown spinules as well as pale hairs. Subcosta without hairs. Hair tuft on base of radius dark brown. Basal portion of radius fully haired. Basal cell absent. Halter . Dull white except basal stem partially darkened. Abdomen. Basal scale light brown, with fringe of light-brown long hairs. Dorsal surface of abdomen dark brown except segment 2 yellow (though median portion of posterior half light brown), covered with dark brown short to long hairs; segments 2 and 5–7 each with pair of shiny dorsolateral or lateral patches, of which those on segment 2 silvery iridescent when illuminated at certain angles, and broadly connected in middle to each other.

Genitalia. Coxite in ventral view ( Fig. 2C ) nearly rectangular, 1.8 times as long as its greatest width. Style in ventral view ( Fig. 2C ) slender, tapered toward apex, somewhat curved inward, with apical spine; style in ventrolateral view ( Fig. 2D ) 2.2 times as long as width at base, moderately tapered toward basal one-third, then slightly tapered toward round apex. Ventral plate in ventral view ( Fig. 2C ) transverse, somewhat widened posteriorly, and densely covered with microsetae on ventral surface except lateral portions widely bare; anterior margin not well defined due to lack of pigmentation, though appearing to produce anteromedially judging from presence of microsetae; posterior margin nearly straight, basal arms of moderate length, directed forward though slightly converged apically; ventral plate in lateral view ( Fig. 2E ) moderately produced ventrally; ventral plate in caudal view ( Fig. 2F ) produced ventrally, moderately covered with microsetae only on central portion; dorsal margin moderately concave. Median sclerite in lateral view ( Fig. 2E ) connected to anterior tip of ventral plate, and directed dorsally; median sclerite in caudal view ( Fig. 2G ) thin, flat, widened apically. Paramere ( Fig. 2H ) slender, with several short to long distinct hooks. Aedeagal membrane ( Fig. 2I ) densely covered with microsetae. Ventral surface of abdominal segment 10 without distinct hairs near posterior margin on each side. Cercus ( Fig. 2J, K ) not small, with 12 or 13 hairs.

Specimen examined. One male (with pupal exuviae and cocoon), reared from a pupa collected from a slowflowing stream (width 1–2 m, water temperature 26.5 ˚C, exposed to sun, elevation 100 m), Negeri Sembilan, 9.XII.2010, by H. Takaoka.

Remark. The male of this species is characterized by the elongate labrum 0.93 times as long as the clypeus, as in the female, and the ventral plate widened posteriorly ( Fig. 2C )

Figures

FIGURE 2. Male of Simulium (Gomphostilbia) tahanense. (A) Third maxillary palpal segment with sensory vesicle (right side; front view). (B) Basitarsus and second tarsomere of hind leg (left side; outer view). (C) Coxites, styles and ventral plate (ventral view). (D) Style (right side; ventrolateral view). (E) Ventral plate with median sclerite (lateral view). (F) Ventral plate (caudal view). (G) Median sclerite (caudal view). (H) Paramere (right side: dorsal view). (I) Aedeagal membrane (caudal view). (J) and (K) Abdominal segment 10 and cerci (right side; J, lateral view: K, caudal view). Scales. 0.05 mm for B; 0.02 mm for A and C– K.