Simulium (Gomphostilbia) chaudinhense 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 : 23-26

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

Female. Nearly as in female of S. (G.) asakoae except following characters. Body length 2.0– 2.2 mm. Head. Frontal ratio 1.6–1.8:1.0:2.2–2.4; frons:head ratio 1.0:4.0–4.8. Labrum 0.5 times length of clypeus. Maxillary palp: proportional lengths of third, fourth, and fifth segments 1.0:1.2:2.7–2.9; sensory vesicle ( Fig. 8 A) small, ellipsoidal (0.2–0.3 times length of third segment), with small opening. Maxillary lacinia with 9–11 inner and 11–15 outer teeth. Mandible with 23 or 24 inner teeth and three or four outer teeth at some distance from tip. Legs. Foreleg: coxa and trochanter yellowish white; femur light brown with apical cap medium brown (though extreme tip yellowish); tibia white except little more than apical one-fourth dark brown, covered with white fine hairs on basal four-fifths; basitarsus moderately dilated, 6.2–6.6 times as long as its greatest width. Midleg: femur light brown with base yellowish white (though inner surface of basal half yellowish white) and apical cap medium brown (though extreme tip yellowish); tibia light brown except basal one-third yellowish white (though inner surface of basal two-thirds yellowish white) and apical cap brownish black, covered with yellowish fine hairs on posterior and inner surfaces of basal two-thirds; tarsus medium to dark brown though basal half or little more of basitarsus yellow. Hind leg: basitarsus 5.7–5.8 times as long as wide, and 0.7 and 0.6–0.7 times as wide as greatest widths of tibia and femur, respectively; calcipala 0.5 times as wide as greatest width of basitarsus; claw with large basal tooth 0.53 times length of claw. Wing. Length 2.0– 2.2 mm. Abdomen. Basal scale light brown, with fringe of whitishyellow hairs. Terminalia . Sternite 8 bare medially, with 14–22 medium-long to long hairs together with one or two slender short hairs on each side. Ovipositor valves moderately covered with microsetae interspersed with two short hairs; inner margins nearly straight or slightly sinuous, somewhat sclerotized. Paraproct in ventral view with three to six sensilla on anteromedial surface; paraproct in lateral view 0.7 times as long as wide, with 19–32 mediumlong to long hairs on ventral and lateral surfaces. Cercus in lateral view 0.33 times as long as wide. Spermatheca ellipsoidal, 1.5–1.6 times as long as its greatest width.

Male. Nearly as in male of S. (G.) asakoae except following characters. Body length 2.0– 2.5 mm. Head. Upper-eye facets in 10 (rarely 9) vertical columns and 12 horizontal rows. Antenna: first flagellomere 1.8 times length of second one. Maxillary palp: proportional lengths of third, fourth, and fifth segments 1.0:1.1:2.5; sensory vesicle small, ellipsoidal (0.2 times length of third segment), and with small opening. Legs. Foreleg: basitarsus moderately dilated, 7.6–7.9 times as long as its greatest width. Hind leg: basitarsus enlarged, wedge-shaped, 3.4 times as long as wide, and 1.0 and 1.2–1.3 times as wide as greatest width of tibia and femur, respectively; calcipala slightly shorter than basal width, and 0.3 times as wide as greatest width of basitarsus. Wing. Length 2.0– 2.1 mm. Subcosta bare or with one to five hairs. Genitalia. Coxite in ventral view 1.9 times as long as its greatest width. Style in ventrolateral view slightly tapered toward apex, with truncated apex, 0.8 times length of coxite. Ventral plate in ventral view with body transverse, 0.5 times as long as wide, and posterior margin somewhat concave medially (though posterior margin slightly convex medially when ventral plate is slightly tilted). Cercus small, rounded, with 17 or 18 hairs.

Pupa. Body length 2.4–2.5 mm. As in pupa of S. (G.) asakoae except following characters. Thorax. Gill ( Fig. 8 B) composed of eight slender thread-like filaments, arranged as [(2+1)+(1+2)]+2 from dorsal to ventral; common basal stalk 0.6–0.7 times length of interspiracular trunk; dorsal and middle triplets sharing short stalk 0.4–0.6 times length of common basal stalk; dorsal triplet composed of one individual filament and two paired filaments with short primary and secondary stalks (primary stalk usually much longer than secondary stalk) or three filaments rarely arising at same level from primary stalk); middle triplet composed of one individual filament and two paired filaments with short primary and secondary stalks (primary stalk usually much longer than secondary stalk, though primary stalk slightly shorter than secondary stalk in one pupa); ventral paired filaments with medium-long stalk 1.1–1.5 times length of common basal stalk; primary stalk of dorsal triplet lying against that of lower pair at angle of 75–90 degrees when viewed laterally; three filaments of dorsal triplet subequal in length (2.0– 2.5 mm long including their own stalks and common basal stalk) and thickness to one another; three filaments of middle triplet subequal in length (2.7–2.9 mm) and thickness; two filaments of ventral pair subequal in length (3.0– 3.1 mm) and thickness to each other. Abdomen. Dorsally, segments 1 and 2 sparsely covered with minute tubercles ( Fig. 8 C); segment 5 bare (though one spine-comb on each side in two pupae); segment 9 with pair of flat triangular terminal hooks ( Fig. 8 D), of which outer margin 2.4–2.9 times length of inner margin and crenulated. Last segment with three grapnel-shaped hooklets on each side. Cocoon. 3.3–4.0 mm long by 2.2–3.0 mm wide.

Mature larva. Body length 4.6–5.1 mm. Body whitish with following grayish and ochreous markings. Grayish markings as in Fig. 8 E: thoracic segment 1 encircled with grayish band (though disconnected ventromedially) narrowly along anterior margin and grayish area on anterior surface of proleg, thoracic segment 2 grayish ventrally and faintly grayish dorsally; all these grayish markings on thorax faded out in some larvae; abdominal segments 1 and 2 each always encircled with dark gray band; abdominal segment 3 rarely grayish ventrally; abdominal segment 4 encircled with light grayish band, though often faded dorsally; abdominal segment 5 encircled with light grayish band, though often faded ventrally or dorsally or entirely; abdominal segment 6 rarely with gray areas laterally and ventrolaterally; abdominal segment 7 rarely with gray areas laterally and ventrally. Ochreous markings as in Fig. 8 F: thoracic segment 1 encircled with ochreous band; thoracic segments 2 and 3 faintly light ochreous dorsally and ventrally; abdominal segment 3 rarely light ochreous dorsally, abdominal segments 4–9 each with distinct ochreous transverse band dorsally, of which those on segments 4–6 often extended laterally and even ventrolaterally, and those of segments 6–8 usually fused to each other laterally, and abdominal segment 7 often with ochreous transverse band ventrally. Head. Head capsule whitish yellow to yellow except dorsomedial area along posterior margin sometimes darkened, eyes-pot region whitish, and lateral area along posterior margin often darkened widely so that two large dark spots and two small dark spots in front of posterior margin appearing to be obscure ( Fig. 8 G), sparsely covered with minute setae (though moderately on dorsal surface); head spots distinctively positive though anterior spots of posterolateral spots usually faint or indistinct; eyebrow not darkened, with small round dark spot above it ( Fig. 8 G). Antenna composed of three articles and apical sensillum, longer than stem of labral fan; proportional lengths of first, second, and third articles 1.0:0.7:0.8– 0.9. Labral fan with 38–42 primary rays. Mandible ( Fig. 8 H) 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 angle of little less than 90 degree against mandible on apical side; supernumerary serrations absent. Hypostoma ( Fig. 8 I) with row of nine apical teeth, of which median tooth is longer than each corner tooth; lateral margin smooth; four or five hypostomal bristles per side lying nearly parallel to lateral margin. Postgenal cleft ( Fig. 8 J) arrow-headshaped (though not pointed apically), medium-long, 2.1–2.6 times length of postgenal bridge. Cervical sclerites composed of pair of small yellow rod-like pieces. Thorax and Abdomen. Thoracic proleg without hairs; thoracic cuticle and abdominal cuticle of segments 1 and 2 almost bare; abdominal cuticle of segments 3 and 4 sparsely covered with minute seate dorsally, that of segments 5–9 moderately covered with slightly darkened unbranched minute setae mixed with unpigmented shorter minute setae ( Fig. 8 K) on dorsal and dorsolateral surfaces; last abdominal segment densely covered with unbranched colorless minute 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 8–11 finger-like secondary lobules. Anal sclerite of usual X-form, with anterior arms 1.1 times as long as 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 74 or 75 rows of hooklets with up to 13 or 14 hooklets per row.

Type material. HOLOTYPE: Male (with its associated pupal exuviae and cocoon) in 80% ethanol) labeled in a vial as [ UMSRP: Vietnam 0 24, Holotype, Simulium (G.) chaudinhense , Male, coll. Vietnam, 11-XII-2015, Takaoka et al.], reared from a pupa collected from a slow-flowing stream (width 1.0 m, depth 5–10 cm, bottom sandy, water temperature 18.0˚C, shaded, elevation 80 m, 19˚30’46.589”N/105˚09’10.470”E), Chau Dinh , Quy Chau , Nghe An Province, northern Vietnam , 11-XII-2015, by H. Takaoka, M. Sofian-Azirun, C.D. Chen & K.W. Lau. PARATYPES: Six females, two males and three mature larvae, labeled in vials as [ UMSRP: Vietnam 0 24, Paratype, Simulium (G.) chaudinhense , coll. Vietnam, 11-XII-2015, Takaoka et al.], same data as those of holotype .

Ecological notes. The pupae and larvae of this new species were attached to grass leaves trailing in the current. Associated species were S. (G.) parahiyangum and S. (G.) unii sp. nov.

Distribution. Vietnam (Nghe An).

Etymology. The species name chaudinhense refers to the locality name, Chau Dinh, where this new species was collected.

Remarks. This new species is similar to S. (G.) asakoae but is distinguished in the female by the shorter sensory vesicle ( Fig. 8 A) and longer claw tooth, in the male by the smaller number of upper-eye facets, in the pupa by the presence of minute tubercles on abdominal segments 1 and 2 ( Fig. 8 C), and in the larva by abdominal segments 1 and 2 each encircled with a grayish band ( Fig. 8 E).

Figures

FIGURE 8. Female, pupa and larva of Simulium (Gomphostilbia) chaudinhense sp. nov. A, Third segment of female maxillary palp with sensory vesicle (right side, front view); B, Anterior half of pupal thorax and basal portion of gill filaments (right side; outer view); C, Tubercles on pupal abdominal segment 1; D, Terminal hooks of pupal abdominal segment 9 (caudal view); E & F, Entire body of mature larvae (both lateral view; E, grayish marking pattern; F, ochreous marking pattern); G, Larval head capsule (lateral view); H, Larval mandible; I, Larval hypostoma; J, Larval head capsule (ventral view); K, Setae on dorsal surface of larval abdominal segment 8. Scale bars. 0.5 mm for E and F; 0.1 mm for B, G and J; 0.02 mm for A, C, D, H, I and K.