Simulium (Simulium) laui 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 : 67-73

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

( Fig. 28 A–31D)

Female. Body length 2.7–3.1 mm. Head. Narrower than thorax. Frons black, shiny, with several dark long stout hairs along each lateral margin and few to several similar hairs just above lower margin; frontal ratio 1.35– 1.40:1.00:1.54–1.56; frons:head ratio 1.00:4.40–4.54. Fronto-ocular area well developed, short, directed laterally and slightly upward. Clypeus black, white pruinose, slightly shiny when illuminated at certain angles, moderately covered with dark-brown long stout hairs along lateral and ventral margins and middle portion widely bare. Labrum 0.65–0.68 times as long as clypeus. Antenna composed of scape, pedicel and nine flagellomeres, medium to dark brown except scape and pedicel whitish-yellow, and base and ventral surface of first flagellomere yellow. Maxillary palp with five segments, medium brown except segments 1 and 2 light brown, proportional lengths of third, fourth, and fifth segments 1.0:1.71:2.30–2.39; third segment ( Fig. 28 A) of normal size; sensory vesicle ( Fig. 28 A) of moderate size (0.39–0.42 times length of third segment) having large opening near apex. Maxillary lacinia with 11 or 12 inner and 12–14 outer teeth. Mandible with 24 or 23 inner and 11 or 12 outer teeth. Cibarium ( Fig. 28 B) with blunt medial projection on posterior margin and without minute processes near base of medial projection. Thorax. As in female of S. (S.) lacduongense sp. nov. Legs. Foreleg: coxa whitish-yellow; trochanter whitish-yellow to yellow; femur yellow except apical half light brown, though anteroventral surface more widely light brown except base yellow; tibia white except apical cap black, with shiny sheen widely on outer surface when illuminated at certain angles; tarsus black, with moderate dorsal hair crest; basitarsus greatly dilated, 5.05–5.37 times as long as its greatest width. Midleg: coxa brownish-black; trochanter medium brown except basal half whitish yellow; femur dark brown except base yellow; tibia white except apical cap dark brown, and with shiny sheen on posterior surface when illuminated at certain angles; tarsus dark brown to brownish-black except basal half of basitarsus whitish. Hind leg: coxa brownish-black; trochanter yellow; femur dark brown except basal onethird yellow and apical cap brownish-black; tibia white to whitish-yellow except apical cap dark brown, and with shiny sheen on posterior surface when illuminated at certain angles; tarsus brownish-black to black except basal three-fifths to two-thirds of basitarsus white and small portion of pedisulcus of second tarsomere somewhat lighter in some females; basitarsus ( Fig. 28 C) nearly parallel-sided, 5.91–6.10 times as long as wide, and 0.70–0.73 and 0.62–0.69 times as wide as greatest widths of hind tibia and femur, respectively; calcipala ( Fig. 28 C) moderately developed, slightly shorter than basal width, and 0.41 times as wide as basitrsus; pedisulcus ( Fig. 28 C) well developed at basal one-third of second tarsomere; all tarsal claws simple. Wing. Length 2.5–2.7 mm. Costa with dark spinules and hairs; subcosta haired except near apex bare; basal section of radial vein bare; R1 with dark spinules and hairs; R2 with hairs; hair tuft on stem vein dark brown; basal cell absent. Halter . White with basal portion darkened. Abdomen. Basal scale medium brown except median portion widely pale, with fringe of pale hairs. Dorsal surface of abdomen brownish-black except basal one-third or one-fourth of segment 2 white, with short dark hairs; tergite 2 shiny, white iridescent when illuminated at certain angles, and tergites 6–8 shiny. Genitalia. Sternite 8 ( Fig. 28 D) bare medially, with 19–28 dark medium-long to long stout hairs on each lateral surface. Ovipositor valves ( Fig. 28 D) triangular though rounded posteomedially, membranous, each moderately covered with microsetae and one dark medium-long hair and one unpigmented short hair, or only one unpigmented short hair, except portion along inner margin widely bare, so thin and transparent that it is difficult to discern inner margins. Genital fork ( Fig. 28 E) of inverted-Y form, with narrow well sclerotized stem; arms of moderate width, each with distinct short and wide projection having pointed apex directed anterodorsally. Paraproct in ventral view ( Fig. 28 F) nearly quadrate, densely covered with minute setae and with 21–37 short to medium-long hairs on lateral and ventral surfaces except anterolateral corner widely unpigmented and bare; medial surface with two to four short sensilla; paraproct in lateral view ( Fig. 28 G) moderately protruded ventrally beyond ventral margin of cercus, and 0.84 times as long as its width. Cercus in lateral view ( Fig. 28 G) short, rounded posteriorly, 0.46 times as long as wide, and with numerous short to medium-long hairs. Spermatheca ( Fig. 28 H) large, globular or ovoid, 1.14–1.17 times as long as wide, well sclerotized except portion of juncture with duct unsclerotized, with no defined surface patterns, and with internal setae; accessory ducts subequal in thickness to each other, and to major duct.

Male. Body length 2.8–3.0 mm. Head. Slightly wider than thorax. Upper eye medium brown, consisting of large facets in 20 or 21 vertical columns and in 21 horizontal rows. Clypeus black, thickly white pruinose, silvery or bluish, shiny when illuminated at certain angles, sparsely covered with dark-brown hairs along and near lateral margins (most of central portion of upper half bare). Antenna composed of scape, pedicel and nine flagellomeres, light to dark brown except scape, pedicel, and base of first flagellomere whitish-yellow; first flagellomere elongate, 1.85–1.91 times as long as second one. Maxillary palp grayish to medium brown, composed of five segments with proportional lengths of third, fourth, and fifth segments 1.0:1.32–1.35:2.60–3.00; third segment ( Fig. 29 A) of normal size; sensory vesicle ( Fig. 29 A) small (0.20–0.23 times as long as third segment), ellipsoidal, and with opening of moderate size. Thorax. As in male of S. (S.) lacduongense sp. nov. Legs. Foreleg: coxa whitish-yellow; trochanter dark brown except base yellowish; femur light brown with apical cap medium brown and basal one-fifth to one-third of upper surface yellow; tibia light to dark brown except outer surface widely white, and with white sheen when illuminated at certain angles; tarsus black, with moderate dorsal hair crest; basitarsus moderately dilated, 5.5–5.9 times as long as its greatest width. Midleg: coxa brownish-black to black; trochanter dark brown though base yellow; femur dark brown; tibia white on basal two-fifths, light brown on rest, though apical cap dark brown; tarsus dark brown except basal one-third or basal half of basitarsus yellow to dark yellow (its border not well defined). Hind leg: coxa brownish-black; trochanter yellow; femur dark brown except base yellow and apical cap brownish-black; tibia brownish-black except basal tip whitish; tarsus ( Fig. 26 B) dark brown to brownish-black except basal two-fifths of basitarsus yellow and portion of pedisulcus of second tarsomere yellowish; basitarsus ( Fig. 29 B) much enlarged, spindle-shaped, slightly widened from base to apical one-fourth, then slightly tapered to apex, 4.07–4.31 times as long as its greatest width, and 0.82–0.87 times as wide as greatest width of hind tibia, which is subequal in width to hind femur; calcipala ( Fig. 29 B) small, shorter than width at base, 0.27 times as wide as greatest width of basitarsus; pedisulcus ( Fig. 29 B) well developed. Wing. Length 2.2 mm. Other features as in female except subcosta bare or with up to five hairs. Halter . White with basal portion darkened. Abdomen. Basal scale brownish-black, with fringe of dark long hairs. Dorsal surface of abdomen brownish-black to black and covered 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. 29 C) nearly quadrate, covered with many stout hairs on posterior half; coxite in ventrolateral view ( Fig. 29 D) rectangular, 0.71 times as long as width. Style in ventral view ( Fig. 29 C) elongate, nearly parallel-sided from base to basal one-third, tapered to little beyond middle, then gradually widened toward apex, with apical spine; style in ventrolateral view ( Fig. 29 E, F) elongate, 3.26 times as long as its greatest width at base, nearly parallel-sided from basal one-third, abruptly narrowed toward middle, then gradually widened toward apex or apical one-fourth; style in medial view ( Fig. 29 G) spatulate dorsoventrally, 1.74 times as long as coxite, with long horn-like basal protuberance, with several minute cone-like spines each having microseta at its apex, on anterior surface, and with pointed apical spine. Ventral plate in ventral view ( Fig. 29 C) with body nearly rectangular (though somewhat narrowed basally, and rounded on each posterolateral corner), with ventromedial process covered with many minute setae on anterior and anterolateral surfaces, and several ridges in two vertical rows on posterior surface; arms directed forward and divergent from each other; ventral plate in lateral view ( Fig. 29 H) having ventromedial process at about right or slightlygreater angle against dorsal margin of body, with serrated posterior margin, and bare except anteroventral surface moderately covered with microsetae; ventral plate in caudal view ( Fig. 29 I) having ventromedial process parallel-sided (though basal portion somewhat narrowed in some males) except apical one-third narrowed toward tip, with rounded bare apex and having several ridges in two vertical rows on posterior surface except apical twofifths without ridges, and few microsetae basally on posterior surface. Median sclerite ( Fig. 29 H, J) plate-like, widened from base toward apex, with round apex, brown basally, but not so well sclerotized apically. Paramere ( Fig. 29 K) with several distinct hooks. Aedeagal membrane ( Fig. 29 L) densely covered with minute spinous setae, and with weakly sclerotized dorsal plate in form of horizontal bar ( Fig. 29 M). Abdominal segment 10 ( Fig. 29 N, O) without distinct hair on ventral and lateral surfaces. Cercus ( Fig. 29 N, O) small, rounded, with 10–15 distinct hairs.

Pupa. Body length 2.9–3.2 mm. Head. Integument ochreous, densely and elaborately covered with small round tubercles; antennal sheath bare except basal portion densely covered with small tubercles; frons with pair of unbranched slender short trichomes with uncoiled apices ( Fig. 30 A) on each side; face with unbranched or bifid medium-long trichome with uncoiled apex ( Fig. 30 B) on each side. Thorax. Integument dark yellow to ochreous, densely and elaborately covered with small round tubercles; thorax on each side with three anterodorsal trichomes with uncoiled apices (anterior and middle trichomes bifid or trifid or quadrifid, long, posterior trichome bifid or trifid, medium-long) ( Fig. 30 C), two anterolateral trichomes (anterior trichome unbranched, medium-long or long, with uncoiled apex, posterior trichome unbranched or bifid, long, with coiled or uncoiled apex) ( Fig. 30 D), one unbranched (rarely bifid) medium-long mediolateral trichome with uncoiled apex ( Fig. 30 E), and three ventrolateral trichomes (anterior trichome unbranched or bifid, slender, medium-long, middle one unbranched or bifid, medium-long or long, ventral one unbranched, long) ( Fig. 30 F). Gill ( Fig. 30 G) with eight slender thread-like short filaments in four pairs (one dorsal, two middle and one ventral), arranged as 2+2+2+2 filaments or 2+(2+2)+2 filaments from dorsal to ventral; common basal stalk very short, with basal fenestra ventrally; dorsal and ventral pairs short-stalked, middle inner pair with short to long stalk (up to 1.7 times length of interspiracular trunk in some pupae), and middle outer pair short to medium-long stalk; two middle pairs sharing short common stalk or not; gill filaments widely divergent basally, upper filament of dorsal pair forming an obtuse angle of about 120 degrees against lower filament of ventral pair when viewed laterally; filaments slightly shortened from dorsal to ventral, with upper filament of dorsal pair longest (1.8–1.9 mm long), and lower filament of ventral pair shortest (1.3–1.5 mm long); relative thickness of eight filaments from dorsal to ventral when basal portions were compared 1.00:0.92–0.95:0.68–0.74:0.58–0.74:0.58–0.74:0.58–0.74:0.55–0.63:0.50–0.63; all filaments medium to dark brown, tapered toward apex, with distinct annular ridges and furrows forming definite reticulate surface patterns, and densely covered with minute tubercles. Abdomen. Similar to that of S. (S.) lacduongense sp. nov. except segment 1 dorsally with one unbranched or bifid slender medium-long seta ( Fig. 30 H) on each side; segment 2 dorsally with one unbranched slender medium-long seta ( Fig. 30 I) and one not so stout and four stout short setae on each side, of which some stout setae are sometime bifid or trifid ( Fig. 30 J). Cocoon. Similar to that of S. (S.) lacduongense sp. nov. except anterolateral window on each side, which is divided into two smaller open spaces in some cocoons; 3.6–4.2 mm long by 1.5–1.6 mm wide.

Mature larva. Body length 5.5–6.0 mm. Body grayish brown, with thorax grayish black. Cephalic apotome ( Fig. 31 A) somewhat variable in color, pale yellow to dark yellow on anterior half, dark yellow to light-brown on posterior half (though medium-brown widely along both lateral margins of posterior two-thirds in some larvae) and narrow area along posterior margin dark brown, with median dark portion slightly extended forward; head spots light to dark brown (with mediolateral spots darkest) except posterior one of posterolateral spots usually indistinct; all spots except mediolateral ones faintly positive in one larva, mediolateral spots and anterior spot of posterolateral ones connected to each other by dark band in some larvae. Lateral surface of head capsule mostly dark yellow on ventral half and light to medium brown on dorsal half except eye-spot region whitish, with two spots near posterior margin merged into dark background or faintly negative, and one small round spot below eye-spot region light to medium brown, or entirely light to medium brown except eye-spot region whitish, with all spots merged into dark background or slightly negative, in several larvae, or entirely dark yellow except eye-spot whitish, with two light brown spots near posterior margin and one small round light-brown spot below eye-spot region, in one larva. Ventral surface of head capsule ( Fig. 31 B) dark yellow to medium brown though area near posterior margin of hypostoma narrowly yellowish, and each side of basal portion of postgenal cleft dark brown; spots on each side of postgenal cleft indistinct or faintly positive or negative. Head capsule sparsely covered with minute setae on its dorsal, lateral and ventral surfaces. Antenna composed of three segments and apical sensillum, slightly longer than stem of labral fan; length ratio of three segments (from base to tip) 1.00:1.39–1.40:0.80–0.83. Labral fan with 35– 40 main rays. Mandible ( Fig. 31 C) 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. 31 D) with nine anterior teeth, of which corner teeth most prominent, slightly longer than median tooth; outer tooth of three intermediate teeth on each side longer than two others; lateral margins weakly serrate apically; five or six hypostomal bristles per side divergent posteriorly from lateral margin. Postgenal cleft ( Fig. 31 B) large, rounded, 2.5–3.0 times as long as postgenal bridge; sheath of subesophageal ganglion pigmented, forming indefinite patterns. Cervical sclerites on each side composed of one medium brown elongate piece and one light brown elliptical piece, not fused to occiput. Histoblast of pharate pupal gill with eight short filaments. 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 14–20 finger-like secondary lobules. Anal sclerite X-shaped, with short broad anterior arms with forked apices, 0.6 times as long as posterior ones and junction with deep unsclerotized incision posteriorly; four to eight sensilla on junction; 7–12 sensilla posterior to posterior arms. Last abdominal segment lacking ventral papillae. Posterior circlet with 93–99 rows of hooklets with up to 16 or 17 hooklets per row.

Type material. HOLOTYPE: Female, reared from a pupa collected from a small shallow stream (width 2–4 m, water temperature 17.0˚C, exposed to the sun, altitude 1,415 m) (12˚01’49.981” N/108˚21’51.175” E) slowly flowing in open land, Suoi Vang, 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. & X.D. Pham. PARATYPES: Eight females, 10 males and 20 mature larvae, same data as those of the holotype.

Biological notes. The pupae and larvae of S. (S.) laui sp. nov. were collected from grass leaves and stalks trailing in the water. Associated species were S. (G.) asakoae and S. (N.) sp. ( S. feuerborni species-group). Three of 61 immature larvae of this new species were infected with microsporidan parasites.

Etymology. The species name laui is in honor of Mr. Koon Weng Lau, PhD student of University of Malaya for his contribution as one of our black-fly research team members.

Remarks. Simulium (S.) laui sp. nov. is assigned to the S. multistriatum species-group of the subgenus Simulium , and is similar to S. (S.) lacduongense sp. nov., from which this new species is distinguished in the female by the bare bsasal section of the radial vein and in the male by the number of upper-eye facets in 20 or 21 vertical columns and 21 horizontal rows, and basal protuberance of the style with pointed apex ( Fig. 29 G). The pupa of this new species is morphologically indistinguishable from that of S. (S.) lacduongense sp. nov.

The pupa of this new species is characterized by the eight gill filaments divergent at an angle of more than 90 degrees ( Fig. 30 G), like S. (S.) lacduongense sp. nov. and eight other related species from Bhutan, India, Nepal and Thailand, as noted in the discussion of S. (S.) lacduongense sp. nov. However, this new species is distinguished from S. (S.) novolineatum by the ventral plate with setae ( Fig. 29 C); from the three other Indian species by the difference in the shape of the ventral plate; from S. (S.) deothangense , S. (S.) kisapense and S. (S.) lampangense by the number of male upper-eye large facets in 20 or 21 vertical columns and 21 horizontal rows (cf., in 17 or 18 vertical columns and 17–19 horizontal rows in the three known species); from S. (S.) hillycum by the female mid tibia which is white except the apical cap dark brown (entirely black in S. (S.) hillycum according to the figure in the original description).

Figures

FIGURE 26. Male of Simulium (Simulium) lacduongense 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, coxite and style (ventrolateral view); E, style (right side; medial view); F, ventral plate and median sclerite (lateral view); G, ventral plate (caudal view); H, median sclerite (ventral 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 28. Female of Simulium (Simulium) laui sp. nov. A, third segment of maxillary palp (right side; front view); B, cibarium (front view); C, basitarsus and second tarsomere of hind leg (left side; outer view); D, sternite 8 and ovipositor valve (right half; ventral view); E, genital fork (ventral view); F & G, paraprocts and cerci (right side; F, ventral view; G, lateral view); H, spermatheca. Scale bars. 0.1 mm for C; 0.02 mm for A, B and D – H.

FIGURE 29. Male of Simulium (Simulium) laui 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, coxite (ventrolateral view); E – G, styles (right side; E & F, ventrolateral view; G, medial view); H, ventral plate and median sclerite (lateral view); I, ventral plate (caudal view); J, median sclerite (ventral view); K, paramere (right side; caudal view); L, aedeagal membrane (caudal view); M, dorsal plate (ventral view); N & O, tenth abdominal segments and cerci (right side; N, lateral view; O, caudal view). Scale bars. 0.1 mm for B; 0.02 mm for A and C – O.

FIGURE 30. Pupa of Simulium (Simulium) laui sp. nov. A, frontal trichomes; B, facial trichome; C – F, thoracic trichomes (C, anterodorsal; D, anterolateral; E, mediolateral; F, ventrolateral); G, gill filaments (right side; outer view); H, hair-like seta on dorsal surface of abdominal segment 1; I, hair-like seta on dorsal surface of abdominal segment 2; J, short stout spinous setae on dorsal surface of abdominal segment 2. Scale bars. 0.1 mm for G; 0.02 mm for A – F, H and I; 0.01 mm for J.

FIGURE 31. Mature larva of Simulium (Simulium) laui sp. nov. A & B, head capsules (A, dorsal view; B, ventral view); C, mandible; D, hypostoma (ventral view). Scale bars. 0.1 mm for A and B; 0.02 mm for C and D.