Simulium (Simulium) congi 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 : 80-84

Simulium (Simulium) congi Takaoka & Sofian-Azirun sp. nov.

( Figs. 35 A–37D)

Female. Unknown.

Male. Body length 2.6 mm. Head. Slightly wider than thorax. Upper eye medium brown, consisting of large facets in 20 vertical columns and in 21 horizontal rows. Clypeus black, thickly white pruinose, silvery or bluish, shiny when illuminated at certain angles, covered with dark-brown hairs along and near lateral margins (most of central portion bare). Antenna composed of scape, pedicel and nine flagellomeres, brownish-black except base of first flagellomere dark yellow or light brown; first flagellomere elongate, 1.53 times as long as second one. Maxillary palp grayish to dark brown, composed of five segments with proportional lengths of third, fourth, and fifth segments 1.0:1.1:2.3; third segment ( Fig. 35 A) of moderate size; sensory vesicle ( Fig. 35 A) small (0.16–0.18 times as long as third segment), ellipsoidal, and with opening of moderate size. Thorax. Scutum black, with white pruinose pattern, i.e., anterior pair of triangular spots (not sharply pointed posteriorly) on shoulders extending posteriorly along lateral margins and connected to large transverse spot entirely covering prescutellar area; these pruinose areas silvery or bluish iridescent when illuminated at certain angles; scutum uniformly and densely covered with brassy recumbent short hairs interspersed with dark-brown long upright hairs on prescutellar area. Scutellum black, with several dark-brown long upright hairs and dark short hairs. Postnotum black, white pruinose when illuminated at certain angles and bare. Pleural membrane bare. Katepisternum longer than deep, brownishblack, white pruinose when illuminated at certain angles, and bare. Legs. Foreleg: coxa medium brown; trochanter dark brown though base somewhat lighter; femur dark brown with apical cap brownish-black; tibia medium brown except both ends brownish-black and outer surface widely white medially, and with bright white sheen when illuminated at certain angles; tarsus brownish-black to black, with moderate dorsal hair crest; basitarsus greatly dilated, 5.6 times as long as its greatest width. Midleg: coxa brownish-black; trochanter dark brown; femur dark brown with apical cap brownish-black; tibia dark brown except apical cap brownish-black; tibia with white sheen on posterior surface when illuminated at certain angles; tarsus dark brown to brownish-black except basal half of basitarsus slightly lighter. Hind leg: coxa dark brown to brownish-black; trochanter medium brown; femur dark brown except apical cap brownish-black; tibia dark brown to brownish-black except basal tip yellow; tarsus ( Fig. 35 B) dark brown except little less than basal half of basitarsus (though base darkened) and little less than basal half of second tarsomere whitish-yellow; basitarsus ( Fig. 35 B) much enlarged, wedge-shaped, gradually widened from base to apical one-third, then nearly parallel-sided up to near apex, 3.9 times as long as its greatest width, and 0.9 and 1.0 times as wide as greatest widths of hind tibia and femur, respectively; calcipala ( Fig. 35 B) small, nearly as long as wide, 0.27 times as wide as greatest width of basitarsus; pedisulcus ( Fig. 35 B) well developed. Halter . White except basal portion darkened. Wing. Length 2.1 mm. Costa with dark spinules and hairs; subcosta bare; basal section of radial vein bare; R1 with dark spinules and hairs; R2 with hairs; hair tuft on base of radial vein dark brown; basal cell absent. Abdomen. Basal scale brownish-black, with fringe of dark long hairs. Dorsal surface of abdomen brownish-black to black, with dark short hairs; segments 2 and 5–7 each with pair of silvery or bluish iridescent spots dorsolaterally, those on segment 2 connected broadly to each other in middle. Genitalia. Coxite in ventral view ( Fig. 35 C) nearly quadrate, covered with stout hairs on posterior half. Style in ventral view ( Fig. 35 C) elongate, gradually tapered from basal one-third to apex, with apical spine (two spines on right style, Fig. 35 C); style in ventrolateral view ( Fig. 35 D) elongate, 3.0 times as long as its greatest width at basal one-third, nearly parallel-sided from base to middle, then slighty tapered toward apex; style in medial view ( Fig. 35 E) 1.6 times as long as coxite, somewhat produced dorsally near base and with several small cone-like spines on dorsal surface. Ventral plate in ventral view ( Fig. 35 C) well sclerotized, with body subquadrate (though somewhat narrowed basally, and rounded on each posterolateral corner), 0.6 times as long as wide, posterior margin somewhat concave, and with round projection directed ventrally which is covered with many minute setae; arms directed forward and somewhat divergent from each other; ventral plate in lateral view ( Fig. 35 F) with posterior margin serrated along basal half; ventral plate in end view ( Fig. 35 G) rounded ventrally, with lateral margin serrated along basal half, with numerous setae on posterior surface except both areas of dorsolateral corners bare. Median sclerite ( Fig. 35 F, H) plate-like, gradually widened from base toward apex, with round apex, brown basally, but not so well sclerotized apically. Paramere ( Fig. 35 I) with several distinct hooks and several smaller ones. Aedeagal membrane sparsely covered with minute setae, and with moderately sclerotized dorsal plate in form of horizontal bar ( Fig. 35 J). Abdominal segment 10 ( Fig. 35 K, L) with two or three hairs on ventral surface and five hairs on lateral surface on each side. Cercus ( Fig. 35 K, L) small, rounded, with eight to ten distinct hairs.

Pupa. Body length 2.3–2.6 mm. Head. Integument including antennal sheaths yellow, without tubercles; frons with two pairs of unbranched slender long trichomes ( Fig. 36 A); face with pair of unbranched long trichomes ( Fig. 36 B). Thorax. Integument yellow, almost bare except narrow portions along anterior margin, along mediolongitudinal line and posterodorsal area sparsely covered with small round tubercles; thorax on each side with two long anterodorsal trichomes ( Fig. 36 C), two anterolateral trichomes (one long, one medium-long) ( Fig. 36 D), one medium-long mediolateral trichome ( Fig. 36 E), and three ventrolateral trichomes (two medium-long, one short) ( Fig. 36 F); all trichomes unbranched. Gill ( Fig. 36 G) with six slender thread-like filaments in three pairs (one dorsal, one middle and one ventral) arising from short common basal stalk; basal fenestra enlarged, balloonlike ( Fig. 36 H); all pairs short-stalked, and stalks of dorsal and ventral pairs lying at angle of 90 degrees when viewed laterally; upper filament of dorsal pair longest (2.1 mm long), gradually shortened from dorsal to ventral, and lower filament of ventral pair shortest (1.2–1.4 mm long); all filaments grayish light-brown except basal portion including stalk of dorsal pair blackish on posterior half of its surface ( Fig. 36 G, H), tapered toward apex, with distinct annular ridges and furrows forming definite reticulate surface patterns, and densely covered with minute tubercles, of which relatively larger ones on ridges. Abdomen. Dorsally, all segments unpigmented except basal half of segment 1 light yellowish; segment 1 with one unbranched medium-long seta on each side; segment 2 with one unbranched seta and five spinous short setae on each side; segments 3 and 4 each with four distinct hooked spines and one unbranched spinous short seta on each side; segments 5 and 6 lacking spine-combs; segments 7–9 with distinct spine-combs in transverse row (though those on segment 7 few in number, 0–3 per side) and comb-like groups of minute spines on each side; segment 9 somewhat yellowish, without terminal hooks. Ventrally, segments 4–8 unpigmented, each with comb-like groups of minute spines; segment 4 with few slender minute setae on each side; segment 5 with pair of bifid stout hooks submedially and few unbranched short setae on each side; segments 6 and 7 each with pair of bifid inner and unbranched outer stout hooks somewhat separated from each other, and few unbranched short setae on each side. Grapnel-shaped hooklets absent on each side of segment 9. Cocoon. Wall-pocket-shaped, moderately woven, thin, ochreous, and not extended ventrolaterally; individual threads visible or not; 3.0– 3.5 mm long by 1.2–1.5 mm wide.

Mature larva. Body length 5.2 mm. Body blackish brown, except ventral surface of abdominal segments 5–9 white though dark line mediolongitudinally on ventral surface of segments 5 and 6. Cephalic apotome (Fig. 37A) dark yellow except posterior two-fifths medium brown though narrow area along both lateral margins paler; head spots almost indistinct or faintly negative. Lateral surface of head capsule medium brown except eye-spot region whitish and areas near anterior margin and ventral margin dark yellow; eyebrow distinct; few spots before posterior margin faintly negative. Ventral surface of head capsule (Fig. 37B) medium brown except hypostoma yellowish; long spot on each side of postgenal cleft faintly negative. Antenna composed of three segments and apical sensillum, slightly longer than stem of labral fan; length ratio of three segments (from base to tip) 1.0:1.3:0.7. Labral fan with 40 main rays. Mandible (Fig. 37C) with serrations composed of two teeth (one medium-sized, one small); main tooth at obtuse angle against mandible on apical side; supernumerary serrations absent; comb-teeth decreasing in length from first to third. Hypostoma (Fig. 37D) with nine anterior teeth, of which corner teeth most prominent, longer than median tooth, which is subequal to outer teeth of intermediate teeth on each side; lateral margins weakly serrate apically; five or six hypostomal bristles per side slightly divergent posteriorly from lateral margin. Postgenal cleft (Fig. 37B) narrow, pointed apically, 6.4 times length of postgenal bridge; sheath of subesophageal ganglion not pigmented. Histoblast of pharate pupal gill with six short filaments and enlarged basal fenestra. Thoracic and abdominal cuticle almost bare except last segment of abdomen moderately covered with short colorless setae on each side of anal sclerite. Rectal scales present. Rectal organ compound, each lobe with 7– 10 finger-like secondary lobules. Anal sclerite X-shaped, with short broad anterior arms about half as long as posterior ones; 12 sensilla posterior to posterior arms. Last abdominal segment somewhat swollen laterally but lacking ventral papillae. Posterior circlet with 80 rows of hooklets with up to 15 hooklets per row.

Type material. HOLOTYPE: Male, reared from a pupa collected from a small stream (width 0.4 m, depth 10 cm, bottom muddy, water temperature 15.0˚C, partially shaded, altitude 1,722 m) (12˚06’06.888” N/ 108˚22’02.797” E) slowly flowing in a swampy area, Dinh Kno, Lac Duong, Lam Dong Province, southern Vietnam, 23-IV-2014, by H. Takaoka, M. Sofian-Azirun, Z. Ya’cob, C.D. Chen, K.W. Lau & X.D. Pham. PARATYPES: One pharate male, one pupa and one mature larva, same data as those of the holotype.

Biological notes. The pupae and larvae of this new species were collected from leaves of trailing grasses and slender pine leaves in a small stream. Associated species were S. (N.) phami and S. (G.) fuscidorsum sp. nov.

Etymology. The species name congi is in honor of Dr. Nguyen Duc Cong, Director, Thong Nhat Hospital, Ho Chi Minh City, for his enthusiastic support of our survey.

Remarks. Simulium (S.) congi sp. nov. is assigned to the S. tuberosum species-group of the subgenus Simulium , redefined by Takaoka and Davies (1996), based on the male genitalia, of which the ventral plate is quadrate or subquadrate when viewed ventrally, having a round projection directed ventrally with serrated posterolateral margins ( Fig. 35 C), and the style has several cone-like spines subbasally on dorsal surface ( Fig. 35 E). This new species is distinguished from all known species of the S. tuberosum species-group by having the swollen basal fenestra at the base of the gills ( Fig. 36 H), a character not reported in species of the S. tuberosum species-group, though reported in several species of certain species-groups of the subgenus Simulium , e.g., S. (S.) bullatum Takaoka & Choochote (of the S. multistriatum species-group) from Thailand, and S. (S.) molliculum Takaoka and S. (S.) laxum Takaoka (both of the S. variegatum species-group) from Sulawesi ( Takaoka and Choochote 2005a; Takaoka 2003), and also in a few other subgenera, e.g., S. (Asiosimulium) suchitrae Takaoka from Nepal, S. (Gomphostilbia) baglungense Takaoka & Shrestha from Nepal, S. (Morops) irianense Takaoka from Irian Jaya, and S. (Nevermannia) chairuddini Takaoka from Sulawesi ( Takaoka and Shrestha 2010; Takaoka 2003).

Figures

FIGURE 35. Male of Simulium (Simulium) congi sp. nov. A, third segment of maxillary palp (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 & E, styles (D, right side, ventrolateral view; E, left side, medial view); F, ventral plate and median sclerite (lateral view); G, ventral plate (caudal view); H, median sclerite (caudal view); I, paramere (right side; caudal view); J, dorsal plate (ventral view); K & L, tenth abdominal segments and cerci (right side; K, lateral view; L, caudal view). Scale bars. 0.1 mm for B; 0.02 mm for A and C – L.

FIGURE 36. Pupa of Simulium (Simulium) congi sp. nov. A, frontal trichome; B, facial trichome; C – F, thoracic trichomes (C, anterodorsal; D, anterolateral; E, mediolateral; F, ventrolateral); G, anterior portion of thorax and gill filaments (right side; outer view); H, basal portion of pupal gill with inflated basal fenestra somewhat produced outward (left side; dorsal view); Scale bars. 0.1 mm for G and H; 0.02 mm for A – F.