Simulium (Gomphostilbia) hongthaii Takaoka, Sofian-Azirun

Takaoka, Hiroyuki, Sofian-Azirun, Mohd, Ya’Cob, Zubaidah, Chen, Chee Dhang, Lau, Koon Weng, Low, Van Lun, Pham, Xuan Da & Adler, Peter H., 2017, The black flies (Diptera: Simuliidae) of Vietnam, Zootaxa 4261 (1), pp. 1-165 : 30-33

Simulium (Gomphostilbia) hongthaii Takaoka, Sofian-Azirun & Ya’cob, 2014

Simulium (Gomphostilbia) hongthaii Takaoka, Sofian-Azirun & Ya’cob (in Takaoka et al., 2014a): 348– 351 (Male and pupa).

This species was described from males and pupae collected from Tam Dao National Park in northern Vietnam ( Takaoka et al. 2014a). The female and larva of this species are here described for the first time.

Female. Body length 2.0– 2.3 mm. Head. Slightly narrower than width of thorax. Frons dark brown, densely covered with yellowish-white scale-like recumbent short hairs interspersed with few dark longer hairs near vertex; frontal ratio 1.6–1.7:1.0:1.9–2.2; frons:head ratio 1.0:4.1–4.2. Fronto-ocular area well developed, narrow, directed dorsolaterally. Clypeus dark brown, densely covered with yellowish-white short hairs interspersed with several dark longer hairs near ventral margin on each side. Labrum 0.65–0.69 times length of clypeus. Antenna composed of scape, pedicel and nine flagellomeres, dark brown except scape, pedicel, and base of first flagellomere yellow. Maxillary palp composed of five segments, light to medium brown except segments 1 and 2 dark yellow, proportional lengths of third, fourth, and fifth segments 1.0:1.1–1.2:2.5–2.6; third segment ( Fig. 11 A) widened; sensory vesicle ( Fig. 11 A) ellipsoidal (0.3–0.4 times length of third segment), with medium-sized opening. Maxillary lacinia with 8 inner and 12–14 outer teeth. Mandible ( Fig. 11 B) with 17–21 inner teeth and lacking outer teeth though outer margin undulate, appearing to have four to six rudimentary teeth. Cibarium ( Fig. 11 C) medially forming sclerotized plate folded forward from posterior margin, with moderately sclerotized mediolongitudinal ridge with bifid apex. Thorax. Scutum dark brown to brownish black except anterolateral calli ochreous, and three blackish longitudinal vittae (one median, two submedian) though not clearly demarcated, thinly pruinose and shiny when illuminated at certain angles, densely covered with whitish-yellow to yellow scale-like recumbent short hairs except three longitudinal vittae covered with dark short hairs. Scutellum ochreous, covered with yellow short hairs and dark-brown longer upright hairs along posterior margin. Postnotum dark brown, whitish-gray pruinose and shiny when illuminated at certain angles, and bare. Pleural membrane bare. Katepisternum longer than deep, medium to dark brown, shiny when illuminated at certain angles, moderately covered with fine short hairs. Legs. Foreleg: coxa and trochanter whitish yellow; femur light brown with apical cap medium brown (though extreme tip yellowish); tibia white except apical one-fourth dark brown, covered with white fine hairs on basal four-fifths; tarsus brownish black, with moderate dorsal hair crest; basitarsus moderately dilated, 6.6 times as long as its greatest width. Midleg: coxa medium brown except posterolateral surface dark brown; trochanter dark yellow with base whitish yellow; femur dark yellow to light brown with basal half of inner surface yellow and apical cap medium brown (though extreme tip yellowish); tibia light brown except basal two-fifths whitish yellow and apical cap dark brown (and apical three-fifths of posterior surface dark brown), covered with whitish and yellowish fine hairs on posterior and inner surfaces of little more than basal half; tarsus dark brown though basal half or little less of basitarsus yellow. Hind leg: coxa light brown; trochanter whitish yellow; femur light brown with base whitish yellow and apical cap medium brown (though extreme tip yellowish); tibia white or yellowish white on basal twothirds and light brown on rest though apical cap brownish black, covered with whitish fine hairs on outer and posterior surfaces of little more than basal three-fourths; tarsus brownish black except basal two-thirds or little more of basitarsus (though base light brown) and basal half of second tarsomere yellowish white; basitarsus ( Fig. 11 D) narrow, nearly parallel-sided though slightly narrowed apically, 7.0 times as long as wide, and 0.6 and 0.6 times as wide as greatest widths of tibia and femur, respectively; calcipala ( Fig. 11 D) nearly as long as width at base, and 0.6 times as wide as greatest width of basitarsus; pedisulcus ( Fig. 11 D) well developed; claw ( Fig. 11 E) with large basal tooth 0.46 times length of claw. Wing. Length 2.2 mm. Costa with dark spinules and hairs except basal patch of hairs yellow. Subcosta with dark hairs except near apex bare. Hair tuft on base of radius yellow. Basal portion of radius fully haired; R1 with dark spinules and hairs; R2 with hairs only. Basal cell absent. Halter . White except basal portion darkened. Abdomen. Basal scale light ochreous, with fringe of whitish-yellow hairs. Dorsal surface of abdomen light to dark brown except segment 2 yellow to light ochreous, moderately covered with dark short to long hairs; tergites of segments 2 and 6–9 shiny when illuminated at certain angles. Ventral surface of segment 2 yellowish white, those of segments 3–5 ochreous and those of other segments medium brown; sternal plate on segment 7 undeveloped. Terminalia . Sternite 8 ( Fig. 11 F) bare medially, with 17–22 medium-long to long hairs together with few slender short hairs on each side. Ovipositor valve ( Fig. 11 F) triangular (though posteromedial corner rounded), thin, membranous, moderately covered with microsetae interspersed with one to three short hairs; inner margins nearly straight or slightly sinuous, somewhat sclerotized, and moderately separated from each other. Genital fork ( Fig. 11 G) of usual inverted-Y form, with slender stem; arms of moderate width, moderately folded medially, without lobe directed posteromedially. Paraproct in ventral view ( Fig. 11 H) somewhat concave anterolaterally, with three or four sensilla on anteromedial surface; paraproct in lateral view ( Fig. 11 I) slightly produced ventrally beyond ventral tip of cercus, 0.7 times as long as wide, with 17–24 medium-long to long hairs on ventral and lateral surfaces. Cercus in lateral view ( Fig. 11 I) short, rounded posteriorly, 0.5 times as long as wide. Spermatheca ( Fig. 11 J) ellipsoidal, 1.4 times as long as its greatest width, well sclerotized except duct and small area near juncture with duct unsclerotized, and with many fissures on outer surface; internal setae absent; both accessory ducts slender, subequal in diameter to major one.

Mature larva. Body length 5.0 mm. Thorax whitish to light ochreous except anterior portion of first segment, proleg and ventral surface of segments 2 and 3 light gray, with reddish-brown transverse band on dorsal surface of segment 1 (though often disconnected medially); abdominal segments 1–4 entirely grayish, abdominal segments 5– 9 light gray on dorsal and dorsolateral surfaces, abdominal segments 5 and 6 each with reddish-brown transverse band dorsally, and abdominal segments 7–9 faintly and irregularly mottled with reddish-brown markings dorsally. Head. Head capsule ( Fig. 12 A) whitish yellow except surrounding areas of posterior spots of posterolateral spots darkened, and sparsely covered with unpigmented minute setae (though moderately on dorsal surface); all head spots on dorsal, lateral and ventral surfaces distinctively positive except anterior spots of posterolateral spots indistinct and posterior spots of posterolateral spots merged into darkened surrounding areas on cephalic apotome; eyebrow faintly visible. Antenna composed of three articles and apical sensillum, longer than stem of labral fan; proportional lengths of first, second, and third articles 1.0:0.7:0.9. Labral fan with 41 primary rays. Mandible ( Fig. 12 C) with three comb-teeth decreasing in length from first tooth to third; mandibular serration composed of two teeth (one medium-sized, one small); major tooth at acute angle against mandible on apical side; supernumerary serrations absent. Hypostoma ( Fig. 12 D) with row of nine apical teeth, of which median tooth is longer than each corner tooth; lateral margin smooth; five hypostomal bristles per side lying slightly divergent posteriorly from lateral margin. Postgenal cleft ( Fig. 12 B) rounded, medium-long, 1.3 times length of postgenal bridge. Cervical sclerites composed of pair of small light-brown rod-like pieces. Thorax and Abdomen. Thoracic proleg without hairs; thoracic cuticle bare; abdominal cuticle of segments 1–6 sparsely covered with unpigmented minute setae on dorsal and dorsolateral surface, and that of segments 7–9 sparsely to moderately covered with slightly darkened unbranched minute setae interspersed with unbranched colorless setae ( Fig. 12 E) on dorsal and dorsolateral surfaces; last abdominal segment densely covered with unbranched colorless longer setae on dorsolateral and lateral surfaces of each side of anal sclerite and on each lateral surface even down to base of ventral papilla; thorax and abdomen without dorsal protuberances. Rectal scales absent. Rectal organ compound, each of three lobes with 11–14 finger-like secondary lobules. Anal sclerite of usual X-form, with anterior arms 1.1 times length of posterior ones, broadly sclerotized at base; no sensilla on broad base and posterior to posterior arms; accessory sclerite absent. Last abdominal segment with pair of large conical ventral papillae. Posterior circlet with 83 rows of hooklets with up to 13 hooklets per row.

Specimens examined. Four females, four males and one mature larva collected from a small moderatelyflowing stream (width 1.5 m, depth 10 cm, water temperature 13.0˚C, partially shaded, elevation 1,105 m, 22˚18’48.273”N/103˚53’10.384”E), Sapa , Lao Cai Province, northern Vietnam, 21-XII-2014, by H. Takaoka, M. Sofian-Azirun, Z. Ya’cob, C.D. Chen & K.W. Lau.

Distribution. Vietnam (Lam Dong, Lao Cai, Thua Thien Hue and Vinh Phuc).

Remarks. The female of S. (G.) hongthaii is similar to that of S. (G.) asakoae originally described from Peninsular Malaysia ( Takaoka and Davies 1995) in many characters including the size of the sensory vesicle ( Fig. 11 A) and leg colors but is distinguished from the latter by the mandible lacking distinct outer teeth ( Fig. 11 B). The larva of this species is distinguished from that of S. (G.) asakoae by the grayish abdominal segments 1–4.

Figures

FIGURE 11. Female of Simulium (Gomphostilbia) hongthaii. A, Third segment of maxillary palp with sensory vesicle (right side; front view); B, Tip of mandible; C, Cibarium (front view); D, Hind basitarsus and second tarsomere (left side; outer view). E, Claw; F, Sternite 8 and ovipositor valve (right side only; ventral view); G, Genital fork (ventral view); H & I, Paraprocts and cerci (H, ventral view; I, lateral view); J, Spermatheca. Scale bars. 0.1 mm for D; 0.02 mm for A, C and E – J; 0.01 mm for B.

FIGURE 12. Larva of Simulium (Gomphostilbia) hongthaii. A & B, Head capsules (A, dorsal view; B, ventral view); C, Mandible; D, Hypostoma; E, Setae on dorsal surface of abdominal segment 8. Scale bars. 0.1 mm for A and B; 0.02 mm for C – E.