Simulium (Gomphostilbia) thuathienense Takaoka & Sofian-Azirun

Takaoka, Hiroyuki, Sofian-Azirun, Mohd, Ya’Cob, Zubaidah, Chen, Chee Dhang, Lau, Koon Weng & Pham, Xuan Da, 2015, The black flies (Diptera: Simuliidae) from Thua Thien Hue and Lam Dong Provinces, Vietnam, Zootaxa 3961 (1), pp. 1-96 : 48-51

Simulium (Gomphostilbia) thuathienense Takaoka & Sofian-Azirun sp. nov.

( Figs. 21 A–22L)

Female (dissected from pupal case). Body length 2.4 mm. Head. Slightly narrower than width of thorax. Frons dark brown, densely covered with yellowish-white recumbent short hairs interspersed with several dark longer hairs along each lateral margin; frontal ratio 1.7:1.0:2.7; frons:head ratio 1.0:5.2. Fronto-ocular area well developed, narrow, directed dorsolaterally. Clypeus dark brown, densely covered with yellowish-white recumbent short hairs interspersed with several dark-brown longer hairs along each lateral margin. Labrum 0.67 times length of clypeus. Antenna composed of scape, pedicel and nine flagellomeres, dark brown except scape, pedicel and basal one-third of first flagellomere yellow. Maxillary palp composed of five segments, light to medium brown, proportional lengths of third, fourth, and fifth segments 1.0:1.0:1.9; third segment ( Fig. 21 A) moderately swollen; sensory vesicle ( Fig. 21 A) oblong, 0.38–0.41 times length of third segment, with medium-sized opening. Maxillary lacinia with 12 or 13 inner and 15 or 16 outer teeth. Mandible with 28 inner and 15 outer teeth. Cibarium ( Fig. 21 B) medially forming short wide sclerotized plate folded forward from posterior margin, and with weakly sclerotized mediolongitudinal ridge with forked apex. Thorax. Scutum dark brown except anterolateral calli ochreous, shiny, thinly grayish-white pruinose when illuminated at certain angles, and densely covered with whitish-yellow recumbent hairs. Scutellum ochreous, covered with whitish-yellow short hairs and with dark-brown long upright hairs along posterior margin. Postnotum dark brown, shiny, thinly grayish-white pruinose and bare. Pleural membrane bare. Katepisternum longer than deep, dark brown, shiny when illuminated at certain angles, and moderately covered with yellow hairs interspersed with dark-brown hairs. Legs. Foreleg: coxa whitish yellow; trochanter light brown; femur dark yellow with apical cap medium brown; tibia whitish yellow with apical onefifth medium brown on outer surface, though light to medium brown except base whitish yellow on inner surface; tarsus dark brown, with moderate dorsal hair crest; basitarsus moderately dilated, 5.8 times as long as its greatest width. Midleg: coxa medium brown; trochanter light brown; femur dark yellow to light brown with base yellow and apical cap medium brown (though extreme tip yellow); tibia light to medium brown except basal two-fifths yellow; tarsus dark brown except base of basitarsus somewhat lighter. Hind leg: coxa light brown; trochanter yellow; femur medium brown except base yellow and apical cap dark brown (though extreme tip yellow); tibia whitish-yellow to yellow except apical one-third dark brown; tarsus dark brown except basal two-thirds of basitarsus (though base light brown) and basal half of second tarsomere yellowish; basitarsus ( Fig. 21 C) narrow, nearly parallel-sided; calcipala nearly as long as wide; pedisulcus well developed; claw ( Fig. 21 D) with large basal tooth 0.5 times as long as claw. Wing. Length not measurable. Costa with dark brown spinules and light to medium brown hairs except basal patch of whitish-yellow hairs. Subcosta with medium brown hairs except near apex bare. Hair tuft of base of radial vein yellow. Basal portion of radius fully haired; R1 with dark brown spinules and light to medium brown hairs; R2 with light to medium brown hairs only. Basal cell absent. Halter . White with basal portion darkened. Abdomen. Basal scale ochreous, with fringe of whitish-yellow hairs. Dorsal surface of abdomen medium brown to brownish-black except basal half of segment 2 yellow, moderately covered with dark-brown hairs interspersed with yellow fine hairs; tergites of segments 2 and 6–9 shiny when illuminated at certain angles; sternal plate on segment 7 undeveloped. Genitalia. Sternite 8 ( Fig. 21 E) bare medially, with 13 or 14 medium-long to long hairs together with few short setae on each side. Ovipositor valves ( Fig. 21 E) triangular, with round posteromedial corners, thin, membranous, moderately covered with microsetae interspersed with two short setae; inner margins nearly straight on basal two-thirds, slightly sclerotized and narrowly separated from each other. Genital fork ( Fig. 21 F) of usual inverted-Y form, with arms of moderate width; arm folded medially, and with projection directed posteromedially (though apical portion not well defined in pharate specimen). Paraproct in ventral view ( Fig. 21 G) much depressed on anteroventral surface along anteromedial margin and with few sensilla on anteromedial surface; paraproct in lateral view ( Fig. 21 H) somewhat produced ventrally, with 19 or 20 medium-long to long hairs on ventral and lateral surfaces. Cercus in lateral view ( Fig. 21 H) short, rounded posteriorly, 0.4 times as long as wide. Spermatheca ( Fig. 21 I) ellipsoidal, 1.4 times as long as wide, well sclerotized except duct and small area at juncture with duct unsclerotized, and with many fissures on outer surface; internal setae absent; both accessory ducts slender, subequal in diameter to each other and slightly thicker than major duct.

Male. Unknown.

Pupa. Body length 2.6 mm. Head. Integument yellow, moderately covered with round tubercles on frons and small area near posterior margin of each lateral surface; antennal sheath bare, and without projections. Frons with three unbranched long trichomes with uncoiled apices ( Fig. 22 A) on each side; all trichomes subequal in length and thickness to one another. Face with pair of trichomes but lost. Thorax. Integument yellow, moderately covered with round tubercles, with three long anterodorsal trichomes with coiled or uncoiled apices ( Fig. 22 B), one long anterolateral trichome with uncoiled apex ( Fig. 22 C) (one of two trichomes lost), one medium-long mediolateral trichome with uncoiled apex ( Fig. 22 D), and three ventrolateral trichomes with uncoiled apices (one medium-long, two short) ( Fig. 22 E), on each side; all trichomes unbranched. Gill ( Fig. 22 F, G) of much inflated structure, composed of basal portion and two branches (directed dorsally and forward, respectively) resembling letter Y when viewed laterally; basal portion with constriction on apical one-third, and each branch with constriction basally; basal portion with four paired and two individual filaments, and each branch with three finger-like projections, of which one projection bears slender filament arising from its apex; surface of inflated portion and all filaments light brown, without any pattern on inflated portions or any transverse ridges or furrows on filaments, and densely covered with minute tubercles. Abdomen. Dorsally, all segments unpigmented except segment 9 yellowish brown; segment 1 without tubercles, with one unbranched slender medium-long seta on each side; segment 2 with one unbranched slender medium-long seta and five minute unbranched setae on each side; segments 3 and 4 each with four hooked spines and one unbranched short seta on each side; segment 5 lacking spine-combs and comb-like groups of minute spines; segments 6–8 each with spine-combs in transverse row and comb-like groups of minute spines on each side; segment 9 with comb-like groups of minute spines in transverse row on each side, and pair of distinct cone-shaped terminal hooks ( Fig. 22 H). Ventrally, segment 4 with one unbranched short hook (similar in shape and size to outer hooks on segments 6 and 7) and few short setae on each side; segment 5 with pair of bifid hooks submedially and few short setae on each side; segments 6 and 7 each with pair of bifid inner and unbranched outer hooks somewhat spaced from each other (segment 7 with additional bifid hook between inner and outer hooks), and few short setae on each side; segments 4–8 each with comb-like groups of minute spines; three grapnel-shaped hooklets present on each side of segment 9. Cocoon ( Fig. 22 I). Wall-pocket-shaped, thinly and compactly woven with no open spaces in weave, somewhat extended ventrolaterally; anterior margin thickly woven; floor loosely woven on posterior half of cocoon; individual threads invisible; 3.0 mm long by 2.2 mm wide.

Mature larva. Body length 4.7–5.0 mm. Body yellowish except thoracic segment 1 encircled faintly with ochreous transverse band, ventral surface of thoracic segments 2 and 3 ochreous, and dorsal and dorsolateral surface of abdominal segments 6–8 reddish purplish, though faded anteriorly to various degrees on segment 6 in most larvae. Head capsule sparsely to moderately covered with unpigmented minute setae. Cephalic apotome yellow, with indistinct or faint positive head spots. Lateral surface of head capsule yellow except eye-spot region white; spots in front of posterior margin indistinct or faintly positive; eyebrow indistinct. Ventral surface of head capsule yellow except basal portioin on each side of postgenal cleft dark brown; elongate spot on each side of postgenal cleft indistinct or faintly negative. Cervical sclerites composed of two small light-brown rod-like pieces, not fused to occiput, widely separated from each other. Antenna composed of three segments and apical sensillum, much longer than stem of labral fan; antenna pale except dorsal surface of first segment somewhat darkened toward base; length ratio of three segments (from base to tip) 1.00:0.66–0.78:0.95–1.00. Labral fan with 32–35 main rays. Mandible ( Fig. 22 J) with three comb-teeth decreasing in length from first to third; serrations composed of two teeth (one large and one small); large tooth at acute angle to mandible on apical side. Hypostoma ( Fig. 22 K) with row of nine apical teeth, of which median tooth nearly as long as or slightly longer than corner teeth, and middle tooth of intermediate teeth shortest; lateral margins smooth; five hypostomal bristles per side nearly parallel to lateral margin on each side. Postgenal cleft ( Fig. 22 L) medium-sized, rounded, 1.1–1.2 times as long as postgenal bridge; sheath of subesophageal ganglion unpigmented, not visible. Pharate pupal gill with wrinkled enlarged body with six short finger-like projections and eight slender thread-like filaments. Thoracic cuticle bare. Abdominal cuticle bare except both sides of anal sclerite (down to base of ventral papillae) densely covered with colorless unbranched setae. Rectal scales absent. Rectal organ compound, each of three lobes with 11–15 finger-like secondary lobules. Anal sclerite X-shaped, anterior arms 1.2 times as long as posterior ones; accessory sclerites absent; sensillum absent. Ventral papillae well developed, conical. Posterior circlet with 84–88 rows of hooklets with up to14 hooklets per row.

Type material. HOLOTYPE: Pharate female, collected from a small stream (width 0.2–0.3 m, depth 2–3 cm, water temperature 17.0˚C, shaded, altitude 1,313 m, 16˚11’41.099” N/107˚51’47.675” E), slowly flowing from a natural forest, near the top of Bach Ma National Park, Phu Loc, Thua Thien Hue Province, central Vietnam, 23-II- 2014, by H. Takaoka, M. Sofian-Azirun, Z. Ya’cob, C.D. Chen & K.W. Lau. PARATYPES: 11 mature larvae, same data as those of the holotype.

Etymology. The species name thuathienense refers to the name of the province, Thua Thien Hue, where this new species was collected.

Biological notes. The pupa and larvae of this new species were collected from dead tree leaves and trailing grasses in the water. The associated species were S. (G.) phulocense sp. nov. and S. (N.) bachmaense .

Remarks. Simulium (G.) thuathienense sp. nov. is placed in the S. gombakense species-group of the subgenus Gomphostilbia , defined by Takaoka (2012), based on the characteristic inflated pupal gill ( Fig. 22 F, G). A similar type of gills is known in S. (G.) antlerum Chen from Hainan Island, China ( Chen 2001), S. (G.) gombakense Takaoka & Davies originally described from Peninsular Malaysia ( Takaoka and Davies 1995; Takaoka 2000; Takaoka et al. 2010b) and later reported from Thailand ( Kuvangkadilok and Takaoka 2000), S. (G.) langkawiense Takaoka, Sofian-Azirun & Ya’cob from Langkawi Island, Peninsular Malaysia ( Takaoka et al. 2013b), S. (G.) nuwakotense Takaoka & Shrestha from Nepal ( Takaoka and Shrestha 2010) and S. (G.) sachini Takaoka & Henry described from Darjeeling, India ( Takaoka et al. 2009a). However, the gill of this new species differs from those of all these known species by the following characteristics (those of related species in parentheses): from S. (G.) antlerum by six slender filaments on the basal inflated portion, and remaining two, each on the forward and dorsal inflated branches (eight slender filaments on the basal inflated portion and two slender filaments on the dorsal inflated branch); from S. (G.) gombakense and S. (G.) langkawiense by the dorsal branch with a basal constriction (without such a constriction); from S. (G.) nuwakotense and S. (G.) sachini by the forward branch with a basal constriction (with two constrictions). In addition, cone-shaped pupal terminal hooks ( Fig. 22 H) separate this new species from all the seven known species of the S. (G.) gombakense species-group, all of which have plate-like pupal terminal hooks with a serrated outer margin.

Figures

FIGURE 21. Female of Simulium (Gomphostilbia) thuathienense sp. nov. A, third maxillary palpal segment (right side; frontal view); B, cibarium (front view); C, basitarsus and second tarsomere of hind leg (left side; outer view); D, claw; E, sternite 8 and ovipositor valve (right half; ventral view); F, genital fork (ventral view); G, paraproct and cercus (right side; ventral view); H, paraproct and cercus (left side; lateral view); I, spermatheca. Scale bars. 0.05 mm for C; 0.02 mm for A, B and E – I; 0.01 mm for D.

FIGURE 22. Pupa and larva of Simulium (Gomphostilbia) thuathienense sp. nov. A – I, pupa; J – L, larva. A, frontal trichome; B – E, thoracic trichomes (B, anterodorsal; C, anterolateral; D, mediolateral; E, ventrolateral); F, gill (slender filaments omitted; right side; dorsal view); G, gill and interspiracular trunk (right side; lateral view); H, terminal hooks (caudal view); I, cocoon (dorsal view); J, mandible; K, hypostoma (ventral view); L, head capsule with postgenal cleft (ventral view). Scale bars. 1.0 mm for I; 0.1 mm for F, G and L; 0.02 mm for A – E, H and K; 0.01 mm for J.