Simulium (Gomphostilbia) dachaisense Takaoka & Lau

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 : 28-34

Simulium (Gomphostilbia) dachaisense Takaoka & Lau sp. nov.

( Figs. 11 A–13G)

Female. Body length 1.8–2.0 mm. Head. Slightly narrower than thorax. Frons black, shiny when illuminated at certain angles, moderately covered with whitish yellow scale-like recumbent short hairs interspersed with few dark longer hairs along each lateral margin; frontal ratio 1.5–1.6:1.0:1.6–1.8; frons:head ratio 1.0:3.9–4.1. Fronto-ocular area well developed, narrow, directed dorsolaterally. Clypeus black, densely covered with whitish-yellow hairs interspersed with dark longer hairs on each side. Labrum 0.7 times as long as clypeus. Antenna composed of scape, pedicel and nine flagellomeres, dark brown except scape, pedicel and basal half or little less of first flagellomere yellow. Maxillary palp composed of five segments, light brown except third segment dark brown, proportional lengths of third, fourth, and fifth segments 1.0:1.2:2.7; third segment ( Fig. 11 A) of moderate size; sensory vesicle ( Fig. 11 A) of medium size, ellipsoidal, 0.36 times as long as third segment and with medium-sized opening. Maxillary lacinia with 10 inner and 12 or 13 outer teeth. Mandible with 21–23 inner and 10 outer teeth. Cibarium ( Fig. 11 B) with strongly sclerotized dorsal margin having short tongue-like plate produced forward and posteriorly, and with well sclerotized mediolongitudinal ridge with deep cleft, of which apices are hidden behind tongue-like plate. Thorax. Scutum black, shiny when illuminated at certain angles, densely covered with yellow scale-like recumbent hairs. Scutellum brownish-black, slightly shiny when illuminated at certain angles, covered with yellow short hairs and dark-brown long upright hairs along posterior margin. Postnotum brownish-black and bare. Pleural membrane bare. Katepisternum longer than deep, brownish-black, shiny when illuminated at certain angles, moderately covered with short hairs. Legs. Foreleg: coxa light brown; trochanter light brown except base paler; femur light to medium brown with apical cap dark brown; tibia medium brown with base and median large portion pale, moderately covered with whitish-yellow short hairs (brightly shiny when illuminated) on outer surface of basal three-fourths; tarsus black, with moderate dorsal hair crest; basitarsus much dilated, 5.4 times as long as its greatest width. Midleg: coxa dark brown to brownish-black; trochanter medium brown except base pale; femur medium brown except apical cap dark brown; tibia light to medium brown except base yellow and apical cap dark brown, and with whitish-yellow short hairs (brightly shiny when illuminated) on outer and posterior surfaces of basal three-fourths; tarsus dark brown except basal half of basitarsus dark yellow. Hind leg: coxa medium brown; trochanter light brown; femur medium brown except extreme basal tip yellow and apical cap dark brown; tibia ( Fig. 11 C) light to medium brown except base yellow and apical two-fifths dark brown, and with dark spot subbasally; tibia moderately covered with whitish-yellow short hairs (brightly shiny when illuminated) on outer and posterior surfaces of basal three-fourths; tarsus ( Fig. 11 D) brownish-black except basal three-fourths of basitarsus (though base light brown) and basal half of second tarsomere whitish; basitarsus ( Fig. 11 D) narrow, nearly parallel-sided, 6.7 times as long as wide, and 0.6 and 0.5 times as wide as greatest widths of tibia and femur, respectively; calcipala ( Fig. 11 D) well developed, nearly as long as wide, and 0.5 times as wide as greatest width of basitarsus; pedisulcus ( Fig. 11 D) well developed; claw ( Fig. 11 E) with small subbasal tooth. Wing. Length 1.7 mm. Costa with dark brown spinules and light brown hairs except subbasal patch of whitish hairs. Subcosta haired except apical one-fourth to one-fifth bare. Hair tuft on base of radial vein dark brown. Basal portion of radius fully haired. Basal cell absent. Halter . Clear white except basal portion darkened. Abdomen. Basal scale light brown, with fringe of yellowish-white hairs. Dorsal surface of abdomen medium brown to brownish-black, 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 creamy, those of other segments gradually darkened from segment 3 to segment 8; sternal plate on segment 7 undeveloped. Genitalia. Sternite 8 ( Fig. 11 F) bare medially, with 7–11 medium-long to long hairs together with one to four slender short hairs on each side. Ovipositor valves ( Fig. 11 F) triangular (though posteromedial corners rounded), tapered laterally, thin, membranous, moderately covered with microsetae interspersed with one to three short hairs; inner margins nearly straight, moderately sclerotized, and somewhat 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 posteromedial lobe or projection. Paraproct in ventral view ( Fig. 11 H) nearly triangular, with anteromedial margin darkened, with five or six sensilla on anteromedial surface; paraproct in lateral view ( Fig. 11 I) somewhat produced ventrally, 0.6 times as long as wide, with 11–15 medium-long to long hairs on ventral and lateral surfaces. Cercus in lateral view ( Fig. 11 I) short, rounded posteriorly, 0.6 times as long as wide. Spermatheca ( Fig. 11 J) ellipsoidal, 1.6 times as long as 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.

Male. Body length 2.4 mm. Head. Sightly wider than thorax. Upper eye medium to dark brown, consisting of 18 vertical columns and 18 horizontal rows of large facets. Face black, whitish-gray pruinose, shiny. Clypeus black, whitish-gray pruinose, shiny, and moderately covered with yellow short hairs interspersed with dark-brown longer hairs. Antenna composed of scape, pedicel and nine flagellomeres, dark brown except scape dark yellow, and pedicel and base of first flagellomere yellow; first flagellomere elongate, 1.8 times as long as second one. Maxillary palp with five segments, light brown except third segment dark brown, proportional lengths of third, fourth, and fifth segments 1.0:1.2:2.5; third segment ( Fig. 12 A) somewhat widened apically; sensory vesicle ( Fig. 12 A) globular or ellipsoidal, small, 0.2 times length of third segment, and with small opening. Thorax. Scutum black, thinly gray pruinose and shiny when illuminated at certain angles on shoulders, along lateral margins and on prescutellar area leaving large central area non-pruinose, densely covered with golden-yellow short hairs except prescutellar area with few dark upright hairs. Other features as in female. Legs. Color nearly as in female except fore tibia medium brown though median large portion paler, mid basitarsus brownish-black except basal one-third or less dark yellow to light brown, and hind tibia ( Fig. 12 B) with narrower whitish basal portion. Fore basitarsus somewhat dilated, 7.1 times as long as its greatest width. Hind basitarsus ( Fig. 12 C) narrow, nearly parallel-sided (though slightly tapered from middle to apex), 5.5 times as long as wide, and 0.5 and 0.6 times as wide as greatest widths of tibia and femur, respectively; calcipala ( Fig. 12 C) well developed, slightly longer than width at base, and 0.4 times as wide as greatest width of basitarsus; pedisulcus ( Fig. 12 C) well developed. Wing. Length 1.5 mm. As in female except subcosta without hairs. Halter . Grayish with basal portion darkened. Abdomen. Basal scale medium brown, with fringe of light-brown long hairs. Dorsal surface of abdomen medium to dark brown except base of segment 2 ochreous, covered with light-brown short to long hairs; segments 2 and 5–7 each with pair of shiny dorsolateral patches. Genitalia. Coxite in ventral view ( Fig. 12 D) nearly rectangular, 1.6 times as long as its greatest width. Style in ventral view ( Fig. 12 D) 0.8 times length of coxite, slender, tapered toward apex, with apical spine; style in ventrolateral view ( Fig. 12 E) gradually tapered from base to round apex. Ventral plate in ventral view ( Fig. 12 D) transverse, 0.5 times as long as wide, with body slightly widened posteriorly, with anterior margin roundly produced anteromedially, posterior margin shallowly concave, and densely covered with microsetae on ventral surface except areas near anterior margin bare; basal arms of moderate length, directed anteriorly, nearly parallel-sided; ventral plate in lateral view ( Fig. 12 F) with posterior portion of body somewhat produced ventrally; ventral plate in caudal view ( Fig. 12 G) narrowed ventrally with ventral margin nearly straight (width:height ratio 1.0:0.5), moderately covered with microsetae on most of posterior surface. Median sclerite ( Fig. 12 F, H) thin, plate-like, wide, arising from slightly anterior to middle of ventral plate, and directed posterodorsally. Paramere ( Fig. 12 I) with three relatively longer hooks and several shorter ones. Aedeagal membrane moderately covered with microsetae, and with no sclerotized dorsal plate. Ventral surface of abdominal segment 10 ( Fig. 12 J, K) somewhat sclerotized basally, without distinct hairs near posterior margin on each side. Cercus ( Fig. 12 J, K) rounded, somewhat produced ventrally, with 10–13 hairs.

Pupa. Body length 2.2–2.4 mm. Head. Integument yellow, moderately covered with small round tubercles; antennal sheath without protuberances; frons with three pairs of unbranched long trichomes with coiled or uncoiled apices; face with pair of unbranched long trichomes with coiled apices; three frontal trichomes on each side arising close together, subequal in length to one another and somewhat longer than facial one. Thorax. Integument yellow, moderately covered with small round tubercles, with three long anterodorsal trichomes (two with coiled apices, one uncoiled apex), two anterolateral trichomes (one with coiled apex, one with uncoiled apex), one medium-long mediolateral trichome with uncoiled apex, and three ventrolateral trichomes with uncoiled apices (one medium long, two short) on each side; all trichomes unbranched. Gill ( Fig. 13 A) composed of eight slender thread-like filaments, arranged as (2+1)+(1+2)+2 filaments from dorsal to ventral, with short common basal stalk having somewhat swollen basal fenestra at base; dorsal triplet arising upward, with short primary and secondary stalks (or with three filaments arising at same level from short primary stalk in one pupa); middle triplet directed forward (and little inward), with short primary and short to medium-long secondary stalk; stalk of ventral pair directed forward and downward, long, 1.5 times length of interspiracular trunk; stalk of ventral pair about twice as thick as primary stalk of middle triplet, which is slightly thicker than that of dorsal triplet; all filaments light to medium brown, gradually tapered toward apices (though filaments of dorsal and middle triplets slender basally, then slightly tapered toward apices); lengths of filaments including their stalk(s) measured in one pupa, of which all gill filaments are intact ( Fig. 13 A), are as follows: filaments of dorsal triplet 0.9–1.1 mm long, those of middle triplet 1.1–1.4 mm long; inner filament (2.9 mm long) of ventral pair slightly longer than outer filament (2.7 mm long); filaments of dorsal and middle triplets subequal in thickness to one another and nearly half as thick as those of ventral paired filaments, when basal portions are compared; cuticle of all filaments with well-defined annular ridges and furrows though gradually becoming indistinct from middle to apices, densely covered with minute tubercles. Abdomen. Dorsally, all segments nearly unpigmented except segments 1 and 2 grayish; segment 1 weakly tuberculate near anterior margin; segment 1 with one unbranched slender medium-long hair-like seta on each side; segment 2 with one unbranched slender medium-long hair-like seta and four or five short somewhat spinous setae submedially near posterior margin on each side; segments 3 and 4 each with four hooked spines and one short somewhat spinous seta near posterior margin on each side; segments 5–8 each with two unbranched short setae near posterior margin on each side; segments 6–9 each with spine-combs in transverse row and comb-like groups of minute spines near anterior margin on each side; segment 9 with pair of cone-like terminal hooks ( Fig. 13 B). Ventrally, segment 4 with one bifid hook and few unbranched short setae on each side; segment 5 with pair of bifid or trifid hooks submedially and few unbranched short slender setae on each side; segments 6 and 7 each with pair of bifid inner and unbranched outer hooks somewhat spaced from each other and few unbranched short slender setae on each side; segments 4–8 with comb-like groups of minute spines. Each side of segment 9 with one to three grapnel-shaped hooklets. Cocoon ( Fig. 13 C). Wall-pocket-shaped, moderately woven, somewhat extended ventrolaterally; anterior margin somewhat thickly woven, without anterodorsal bulge or projection; posterior half with floor roughly or moderately woven; individual threads visible; 2.5–3.0 mm long by 1.4–2.0 mm wide.

Mature larva. Body length 3.7–4.2 mm. Body light grayish-green though intersegmental areas pale, with reddish-brown markings as follows: thoracic segment 1 encircled with broad transverse band (though disconnected ventromedially) and thoracic segment 3 and abdominal segments 1–8 each with pair of dorsolateral spots increasing width from thoracic segment 3 to abdominal segment 5, though those on posterior segments 6 and 7 less distinct. Cephalic apotome dull yellowish though whitish on little less than anterior half, and moderately covered with unpigmented minute setae; head spots indistinct or faintly negative. Lateral surface of head capsule whitish yellow except eye-spot region whitish; eyebrow somewhat darkened on posteror half, two relatively large spots and one small spot near posterior margin faintly positive or indistinct; one or two small spots below eye-spot region indistinct. Ventral surface of head capsule whitish yellow except darkened area near posterior margin on each side of postgenal cleft; one elongate spot and one round spot on each side of postgenal cleft indistinct. Antenna composed of three segments and apical sensillum, somewhat longer than stem of labral fan; length ratio of three segments (from base to tip) 1.00:0.92–0.95:1.00–1.11. Labral fan with 30–35 main rays. Mandible ( Fig. 13 D) with three comb-teeth decreasing in length from first to third; serrations composed of two teeth (one medium-sized, one small); major tooth at acute angle against mandible on apical side; supernumerary serrations absent. Hypostoma ( Fig. 13 E) with row of nine apical teeth, of which median tooth and each corner tooth are prominent; lateral margin smooth; four or five hypostomal bristles per side lying parallel to lateral margin. Postgenal cleft ( Fig. 13 F) deep, 6.3–6.6 times length of postgenal bridge. Cervical sclerites composed of two pale small pieces, not fused to occiput, widely separated medially from each other. Cuticle of abdominal segments 5–9 densely covered with dark unbranched and bifid (and rarely trifid) spinous setae of various sizes (apex of each dark seta appearing to have few to several transparent tips) ( Fig. 13 G) dorsally and dorsolaterally; cuticle of thorax and abdominal segments 1–4 sparsely with relatively smaller similar dark setae; last abdominal segment moderately covered also with unbranched colorless setae on each side of anal sclerite. Rectal scales present. Rectal organ retracted, number of secondary lobules per lobe uncountable. Anal sclerite of usual X-form, with anterior arms 0.7 times as long as posterior ones, broadly sclerotized at base; accessory sclerite absent. Last abdominal segment expanded ventrolaterally forming double bulges on each side, visible as large conical ventral papilla when viewed from side. Posterior circlet with 69–72 rows of hooklets with up to 13 or 14 hooklets per row.

Type material. HOLOTYPE: Female, reared from a pupa collected from a small shallow stream (width 3–6 m, depth 10–20 cm, bottom sandy, water temperature 20.0˚C, exposed to the sun, altitude 1,440 m) (12˚08’32.409” N/108˚38’58.318” E) slowly flowing in open land, Da Chais, Lac Duong, Lam Dong Province, southern Vietnam, 24-IV-2014, by H. Takaoka, M. Sofian-Azirun, Z. Ya’cob, C.D. Chen & K.W. Lau. PARATYPES: One female, one male, one pharate female, one pharate male, three pupal exuviae and cocoons, and four mature larvae, same data as those of the holotype.

Biological notes. The pupae and larvae of this new species were collected from grasses trailing in the water. Associated species were S. (S.) lacduongense sp. nov. and S. (S.) nodosum .

Etymology. The species name dachaisense refers to the area name, Da Chais, where this new species was collected.

Remarks. This new species is assigned to the Simulium batoense species-group of the subgenus Gomphostilbia , redefined by Takaoka (2012), based on the antenna with nine flagellomeres, pleural membrane bare, hind tibiae mostly darkened ( Fig. 11 C), spermatheca without sclerotized neck ( Fig. 11 J), male hind basitarsus slender and parallel-sided ( Fig. 12 C), ventral plate slightly produced ventrally ( Fig. 12 G) (its ratio of the height against the greatest width is 0.5), and pupal gill with eight filaments ( Fig. 13 A).

Among six subgroups of the S. batoense species-group (Takaoka 2012), S. (G.) dachaisense sp. nov. is placed in the S. duolongum subgroup (22 known species included) by having the pupal gill with eight filaments, of which two filaments of the ventral pair are subequal in length and thickness to each other, longer than the pupal body, and more than 1.5 times as long as other six filaments of the dorsal and middle triplets ( Fig. 13 A).

This new species is characterized in the female by the claw having a small subbasal tooth ( Fig. 11 E), a character reported only in two species of the S. batoense species-group, i.e., S. (G.) batoense Edwards described from Java, and S. (G.) pattoni Senior-White from Sri Lanka ( Takaoka and Davies 1996; Davies and Györkös 1987). However, S. (G.) dachaisense sp. nov. is distinguished from S. (G.) batoense by the following characters (those of S. (G.) batoense in parentheses): in the female by lacking three dark longitudinal vittae on the scutum (with three dark longitudinal vittae); in the male by the slenderer hind basitarsus, length ratio against the greatest width 5.5 (cf., 4.6), and ventral plate with its ventral margin nearly straight when viewed posteriorly ( Fig. 12 D) (the ventral plate rounded ventrally); in the pupa by the gill filaments arranged as (2+1)+(1+2)+2 filaments ( Fig. 13 A) (2+1+(1+2)+2 filaments) and cone-shaped terminal hooks ( Fig. 13 B) (terminal hooks flat triangular-shaped with its outer margin undulate or weakly serrated); and in the larva by the shape of dark spinous setae on dorsal and dorsolateral surfaces of posterior abdominal segments, which are unbranched or bifid ( Fig. 13 G) (basally branched into two to four).

Simulium (G.) dachaisense sp. nov. is distinguished from S. (G.) pattoni in the female by lacking three longitudinal vittae on the scutum, in the male by the narrower fore and hind basitarsi (the length ratios against the greatest widths 7.1 and 5.5, respectively, in this new species versus 5.7 and 3.8 in S. (G.) pattoni ), and ventral plate with its ventral margin nearly straight when viewed posteriorly ( Fig. 12 D) (cf., ventral plate somewhat pointed ventrally in S. (G.) pattoni ), and in the pupa by the different arrangement of the gill filaments (cf., 1+2+(1+2)+2 filaments in S. (G.) pattoni ).

Figures

FIGURE 11. Female of Simulium (Gomphostilbia) dachaisense sp. nov. A, third segment of maxillary palp (right side; front view); B, cibarium (front view); C, tibia of hind leg (left side; outer view); D, basitarsus and second tarsomere of hind leg (left side; outer view); E, claw; F, sternite 8 and ovipositor valve (right half; ventral view); G genital fork (ventral view); H & I, paraprocts and cerci (right side; H, ventral view; I, lateral view); J, spermatheca. Scale bars. 0.1 mm for C and D; 0.02 mm for A, B and F – J; 0.01 mm for E.

FIGURE 12. Male of Simulium (Gomphostilbia) dachaisense sp. nov. A, third segment of maxillary palp (right side; front view); B, tibia of hind leg (left side; outer view); C, basitarsus and second tarsomere of hind leg (left side; outer view); D, coxites, styles and ventral plate (ventral view); E, style (right side; ventrolateral view); F, ventral plate and median sclerite (lateral view); G, ventral plate (caudal view); H, median sclerite (ventral view); I, paramere (right side; posterolateral view); J & K, tenth abdominal segments and cerci (right side; J, lateral view; K, caudal view). Scale bars. 0.1 mm for B and C; 0.02 mm for A and D – K.

FIGURE 13. Pupa and mature larva of Simulium (Gomphostilbia) dachaisense sp. nov. A – C, pupa; D – G, larva. A, gill filaments (right side; outer view); B, terminal hooks (caudal view); C, cocoon (dorsal view); D, mandible; E, hypostoma (ventral view); F, head capsule with postgenal cleft (ventral view); G, dark spinous setae on dorsal surface of abdominal segment 6 (dorsal view). Scale bars. 1.0 mm for C; 0.1 mm for A and F; 0.02 mm for B, D, E and G.