Simulium (Gomphostilbia) unii Takaoka & Pham

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 : 42-49

Simulium (Gomphostilbia) unii Takaoka & Pham sp. nov.

Female. Body length 2.0– 2.5 mm. Head. Slightly narrower than width of thorax. Frons brownish black, densely covered with yellowish-white scale-like recumbent short hairs interspersed with few dark longer hairs near vertex; frontal ratio 1.8:1.0:2.3–2.5; frons:head ratio 1.0:4.6. Fronto-ocular area well developed, narrow, directed dorsolaterally. Clypeus brownish black, densely covered with yellowish-white scale-like hairs interspersed with 10–12 dark longer hairs on each side. Labrum 0.6 times length of clypeus. Antenna composed of scape, pedicel and nine flagellomeres, light to medium brown except scape, pedicel, and basal half of first flagellomere yellow. Maxillary palp composed of five segments, light to medium brown, proportional lengths of third, fourth, and fifth segments 1.0:1.1:2.4–2.5; third segment ( Fig. 17 A) widened apically; sensory vesicle ( Fig. 17 A) small, ellipsoidal (0.2 times length of third segment), with small opening. Maxillary lacinia with 10–12 inner and 15–17 outer teeth. Mandible ( Fig. 17 B) with 28 or 29 inner teeth and one or two outer teeth at some distance from tip. Cibarium ( Fig. 17 C) medially forming sclerotized plate folded forward from posterior margin, with moderately sclerotized mediolongitudinal ridge with bifid apex. Thorax. Scutum dark brown except anterolateral calli ochreous, and three blackish longitudinal vittae (one median, two submedian), thinly pruinose and shiny when illuminated at certain angles, densely covered with whitish-yellow to yellow scale-like recumbent short hairs except three longitudinal vittae covered with dark short hairs. Scutellum ochreous, covered with yellow short hairs and dark-brown longer upright hairs along posterior margin. Postnotum dark brown, slightly shiny when illuminated at certain angles, and bare. Pleural membrane bare. Katepisternum longer than deep, medium to dark brown, shiny when illuminated at certain angles, moderately covered with fine short hairs. Legs. Foreleg: coxa whitish yellow; trochanter light brown except base whitish yellow; femur light brown with apical cap medium brown (though extreme tip yellowish); tibia white except apical one-fourth dark brown, covered with white fine hairs on basal four-fifths; tarsus brownish black, with moderate dorsal hair crest; basitarsus moderately dilated, 6.4–6.8 times as long as its greatest width. Midleg: coxa yellow with light brown basal portion except posterolateral surface dark brown; trochanter whitish yellow; femur light brown with base yellow (though inner surface of basal half yellow) and apical cap medium brown (though extreme tip yellowish); tibia medium to dark brown except basal one-third whitish yellow (though inner surface of basal two-thirds yellow), covered with whitish and yellowish fine hairs on posterior and inner surfaces of basal two-thirds; tarsus dark brown though basal half or little less of basitarsus yellow. Hind leg: coxa light brown except anterior two-fifths yellow; trochanter whitish yellow; femur light to medium brown with base whitish yellow and apical cap dark brown (though extreme tip yellowish); tibia ( Fig. 17 D) yellowish white on basal two-thirds and brownish black on rest, covered with whitish fine hairs on outer and posterior surfaces of little more than basal three-fourths; tarsus brownish black except basal two-thirds or little more of basitarsus (though base light brown) and basal half of second tarsomere yellowish white; basitarsus ( Fig. 17 E) narrow, nearly parallel-sided though slightly narrowed apically, 6.0–6.1 times as long as wide, and 0.7 and 0.6 times as wide as greatest widths of tibia and femur, respectively; calcipala ( Fig. 17 E) nearly as long as width at base, and 0.5 times as wide as greatest width of basitarsus; pedisulcus ( Fig. 17 E) well developed; claw ( Fig. 17 F) with large basal tooth 0.5 times length of claw. Wing. Length 2.0– 2.2 mm. Costa with dark spinules and hairs except basal patch of hairs yellow. Subcosta with dark hairs except near apex bare. Hair tuft on base of radius yellow. Basal portion of radius fully haired; R1 with dark spinules and hairs; R2 with hairs only. Basal cell absent. Halter . White except basal portion darkened. Abdomen. Basal scale yellow, with fringe of whitish-yellow hairs. Dorsal surface of abdomen light to dark brown except anterior two-thirds of segment 2 whitish, 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 yellowish white, that of segment 3 dark yellow and those of other segments medium brown; sternal plate on segment 7 undeveloped. Terminalia . Sternite 8 ( Fig. 17 G) bare medially, with 17–28 medium-long to long hairs together with two to four slender short hairs on each side. Ovipositor valve ( Fig. 17 G) triangular (though posteromedial corner rounded), thin, membranous, moderately covered with microsetae interspersed with two short hairs; inner margins nearly straight or slightly sinuous, somewhat sclerotized, and moderately separated from each other. Genital fork ( Fig. 17 H) of usual inverted-Y form, with slender stem; arms of moderate width, moderately folded medially, without lobe directed posteromedially. Paraproct in ventral view ( Fig. 17 I) somewhat concave anterolaterally, with three to six sensilla on anteromedial surface; paraproct in lateral view ( Fig. 17 J) slightly produced ventrally beyond ventral tip of cercus, 0.7 times as long as wide, with 25–30 medium-long to long hairs on ventral and lateral surfaces. Cercus in lateral view ( Fig. 17 J) short, rounded posteriorly, 0.5 times as long as wide. Spermatheca ( Fig. 17 K) ellipsoidal, 1.2–1.5 times as long as its 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 2.1–2.4 mm. Head. Somewhat wider than thorax. Upper eye medium brown, consisting of 13 or 14 vertical columns and 14 horizontal rows of large facets. Face brownish black, white pruinose. Clypeus brownish black, whitish pruinose, densely covered with golden-yellow scale-like medium-long hairs (mostly directed upward) interspersed with several dark-brown unbranched longer hairs. Antenna composed of scape, pedicel and nine flagellomeres, yellowish except flagellomeres 5–9 or 6–9 light to medium brown; first flagellomere elongate, 1.8 times length of second one. Maxillary palp light to medium brown, with five segments, proportional lengths of third, fourth, and fifth segments 1.0:1.1:2.2; third segment ( Fig. 18 A, B) slender; sensory vesicle ( Fig. 18 A, B) small, globular or ellipsoidal (0.1 times length of third segment), and with small opening. Thorax. Scutum dark brown, without longitudinal vittae, shiny and thinly gray pruinose on shoulders, on wide area along each lateral margin and on prescutellar area when illuminated at certain angles, and densely covered with golden-yellow scale-like recumbent short hairs. Scutellum medium brown, covered with yellow short hairs and dark-brown long upright hairs along posterior margin. Postnotum dark brown, slightly shiny and white pruinose when illuminated at certain angles, and bare. Pleural membrane bare. Katepisternum medium brown, longer than deep, shiny when illuminated at certain angles, moderately covered with fine short hairs. Legs. Foreleg: coxa whitish yellow; trochanter light brown with base whitish yellow; femur light brown with apical cap medium brown (though apical tip yellowish); tibia yellow except basal one-third light brown and apical one-third medium brown, and covered with yellow hairs on basal two-thirds of outer surface; tarsus brownish black; basitarsus moderately dilated, 7.6–7.8 times as long as its greatest width. Midleg: coxa light brown except posterior surface dark brown; trochanter yellowish; femur light brown with base yellowish and apical cap medium brown (though apical tip yellow); tibia medium brown except basal one-third yellowish; tarsus dark brown except basal half of basitarsus yellow (border not well defined). Hind leg: coxa light brown though apical portion yellow; trochanter yellow; femur light to medium brown with base narrowly yellow and apical cap dark brown (though apical tip whitish yellow); tibia ( Fig. 18 C) medium to dark brown except little less than basal half whitish yellow and apex brownish black, covered with yellow hairs on basal three-fourths of outer and posterior surface; tarsus ( Fig. 18 D) medium to dark brown except basal half or little more of basitarsus and basal half of second tarsomere whitish yellow; basitarsus ( Fig. 18 D) enlarged, spindle-shaped, 4.3–4.6 times as long as wide, and 0.8–0.9 and 0.8 times as wide as greatest width of tibia and femur, respectively; calcipala ( Fig. 18 D) nearly as long as basal width, and 0.4 times as wide as greatest width of basitarsus. Pedisulcus ( Fig. 18 D) well developed. Wing. Length 1.9–2.0 mm. Other characters as in female except subcosta bare. Halter . Grayish white except basal stem darkened and apical half grayish ochreous. Abdomen. Basal scale medium brown, with fringe of light-brown hairs. Dorsal surface of abdomen dark brown to brownish black except anterior one-third of segment 2 yellowish, covered with dark-brown short to long hairs; segments 2 and 5–8 each with pair of shiny dorsolateral or lateral patches; ventral surface of segments 2 and 3 whitish though sternal plate of segment 3 darkened, and those of other segments medium to dark brown. Genitalia. Coxite in ventral view ( Fig. 18 E) nearly rectangular, 1.9 times as long as its greatest width. Style in ventral view ( Fig. 18 E) bent inward, with blunt apex having single spine; style in ventrolateral view ( Fig. 18 F) slightly tapered toward apex, with truncated apex. Ventral plate in ventral view ( Fig. 18 E) with body transverse, 0.6 times as long as wide, with anterior margin produced anteromedially, and posterior margin somewhat concave medially (though posterior margin slightly convex medially when ventral plate is slightly tilted), slightly narrowed medially, then nearly parallel-sided, and densely covered with microsetae on ventral surface; basal arms of moderate length, directed forward; ventral plate in lateral view ( Fig. 18 G) moderately produced ventrally; ventral plate in caudal view ( Fig. 18 H) gently rounded ventrally, densely covered with microsetae on posterior surface. Median sclerite ( Fig. 18 I) plate-like and wide. Parameres ( Fig. 18 J) of moderate size, each with four distinct long and medium-long stout hooks, and without minute setae on outer surface of basal arm. Aedeagal membrane ( Fig. 18 J) moderately setose; dorsal plate not defined. Ventral surface of abdominal segment 10 ( Fig. 18 K, L) without distinct hairs near posterior margin. Cercus ( Fig. 18 K, L) small, rounded, with 14–16 hairs.

Pupa. Body length 2.4–2.5 mm. As in S. (G.) sanchayense sp. nov. except following characters. Thorax. Gill ( Fig. 19 A, B, C) composed of eight slender thread-like filaments, arranged as [(2+1)+(2+1)]+2, or [3+(2+1)]+2, or [(2+1)+3]+2, or (3+3)+2 from dorsal to ventral, with short common basal stalk having somewhat swollen basal fenestra ventrally at base; common basal stalk 0.6–0.8 times length of interspiracular trunk; dorsal and middle triplets sharing short stalk 0.6–0.9 times length of common basal stalk; dorsal and middle triplets each composed of one individual filament and two paired filaments with short primary and secondary stalks (secondary stalk usually much shorter than primary stalk but in left gill of one pupa secondary stalk is exceptionally long, twice length of primary stalk as shown in Fig. 19 C), or three filaments arising at same level from primary stalk; ventral paired filaments with medium-long stalk 0.9–1.5 times length of common basal stalk; primary stalk of dorsal triplet lying against that of ventral pair at angle of 90 degrees or little greater when viewed laterally; all filaments medium brown, gradually tapered toward apex; three filaments of dorsal triplet subequal in length (2.3–2.5 mm long including their own stalks and common basal stalk) and thickness to one another; three filaments of middle triplet subequal in length (2.6–3.0 mm) and thickness; inner filament of ventral pair longest (2.8–3.2 mm), slightly longer than outer filament (2.7–3.1 mm); two filaments of ventral pair subequal in thickness to each other, and 1.2–1.5 times as thick as six other filaments when compared basally; cuticle of all filaments with well-defined annular ridges and furrows, and densely covered with minute tubercles. Abdomen. Dorsally, segments 1, 2 and 9 yellow, and other segments whitish yellow at least medially; segment 9 with pair of flat triangular terminal hooks, of which outer margin 1.8 times length of inner margin and crenulated ( Fig. 19 D). Cocoon ( Fig. 19 E, F). Wall-pocketshaped, moderately woven, widely extended ventrolaterally; anterior margin thickly woven medially, with dorsomedial projection, resembling letter W when viewed dorsally; posterior three-fifths with floor roughly woven; individual threads visible; 3.0– 3.9 mm long by 2.0– 2.9 mm wide.

Mature larva. Body length 4.4–5.5 mm. Body whitish to light ochreous, with following color markings: thoracic segment 1 encircled with reddish-brown band (though often disconnected ventromedially), proleg light ochreous, thoracic segments 2 and 3 reddish brown on ventral surface, though lighter on segment 3; abdominal segments 1 and 2 each encircled by grayish broad band; abdominal segments 3 and 4 each with or without pair of narrow light reddish-brown dorsolateral spots; abdominal segment 5 encircled by distinct reddish-brown transverse band though disconnected ventromedially, abdominal segment 6 with similar colored transverse band (though much narrower) on dorsal and dorsolateral surfaces, though often faded to varying extent leaving reddish-brown round spot dorsomedially, and pair of light reddish-brown spots ventrally; abdominal segments 7 and 8 widely reddish brown on dorsal and dorsolateral surfaces, though faded to varying extent anteromedially; abdominal segment 7 with reddish-brown narrow transverse band ventrally. Head. Head capsule whitish yellow, sparsely covered with minute setae (though moderately on dorsal surface); head spots faintly positive though two relatively large spots near posterior margin on lateral surface usually moderately positive, and two small spots below eyespot region often indistinct; eyebrow indistinct. Antenna composed of three articles and apical sensillum, longer than stem of labral fan; proportional lengths of first, second, and third articles 1.0:0.6–0.8:0.9. Labral fan with 36– 41 primary rays. Mandible ( Fig. 20 A) 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 acute angle against mandible on apical side; supernumerary serrations absent. Hypostoma ( Fig. 20 B) 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 slightly divergent posteriorly from lateral margin. Postgenal cleft ( Fig. 20 C) rounded, medium-long, 1.4 times length of postgenal bridge. Cervical sclerites composed of pair of small unpigmented rod-like pieces. Thorax and Abdomen. Thoracic proleg without hairs; thoracic cuticle almost bare; abdominal cuticle of segments 1–6 almost bare, and that of segments 5–9 sparsely covered with slightly darkened unbranched or bifid or trifid minute setae ( Fig. 20 D) on dorsal and dorsolateral surfaces; last abdominal segment densely covered with unbranched colorless longer 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 six to nine finger-like secondary lobules. Anal sclerite of usual Xform, with anterior arms nearly 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 68 rows of hooklets with up to 12 hooklets per row.

Type material. HOLOTYPE: Female (with its associated pupal exuviae and cocoon) in 80% ethanol, labeled in a vial as [ UMSRP: Vietnam 0 28, Holotype, Simulium (G.) unii , Female, 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, three males and two mature larvae, same data as those of holotype, labeled in each vial as [ UMSRP: Vietnam 0 28, Paratype, Simulium (G.) unii , coll. Vietnam, 11-XII-2015, Takaoka et al.].

Biological notes. The pupae and larvae of this new species were collected from fallen leaves and grasses tailing in the current. Associated species were S. (G.) chaudinhense sp. nov., S. (G.) parahiyangum , S. (S.) nodosum and S. (S.) tani (complex).

Etymology. The species name unii is in honor of Prof. Sigehiko Uni, Institute of Biological Sciences, Faculty of Science, University of Malaya, for his great contribution to taxonomic studies of filariae of wild animals in relation to zoonotic onchocerciasis in Japan.

Distribution. Vietnam (Nghe An).

Remarks. Simulium (G.) unii sp. nov. is placed in the S. asakoae species-group by having the yellow hair tuft on the base of the radius and enlarged male hind basitarsus ( Fig. 18 D), although the ventral plate of this new species is not clearly emarginated on each lateral margin ( Fig. 18 E), a character disagreeing with one of the key characters of this species-group defined by Takaoka (2012).

This new species is characterized by the cocoon having an anterodorsal projection ( Fig. 19 E). Among the 25 species of the S. asakoae species-group (Takaoka 2012; Takaoka et al. 2014a, d, 2015a), S. (G.) gyorkosae Takaoka & Davies from Java, Indonesia ( Takaoka and Davies 1996); S. (G.) fanjingshanense Chen, Zhang & Wen from Guizhou, south China ( Chen et al. 2000); S. (G.) fuscidorsum Takaoka & Ya’cob from Vietnam ( Takaoka et al. 2015a); S. (G.) phulocense Takaoka & Chen from Vietnam ( Takaoka et al. 2015a); and S. (G.) yunnanense Chen & Zhang from Yunnan, China (Chen and Zhang 2004) have a similar cocoon. However, S. (G.) unii sp. nov. is distinguished from these five known species by the following characters (those of each related species in parentheses): from (G.) gyorkosae by the number of male upper-eye facets in 13 or 14 vertical columns (in 10 or 11 vertical columns); from S. (G.) fanjingshanense by the female hind tibia which is yellowish on the basal two-thirds ( Fig. 17 D) (yellowish on the basal two-fifths), and angle of the stalk of the dorsal triplet against that of the ventral pair of pupal gill filaments when viewed laterally being 90 degrees or slightly greater ( Fig. 19 A) (60 degrees); from S. (G.) fuscidorsum by the small female sensory vesicle ( Fig. 17 A) (enlarged sensory vesicle) and short common basal stalk ( Fig. 19 A) (long common basal stalk); from S. (G.) phulocense by the female hind tibia which is yellowish on the basal two-thirds ( Fig. 17 D) (yellowish on the basal half), and angle of the stalk of the dorsal triplet against that of the ventral pair of pupal gill filaments when viewed laterally being 90 degrees or slightly greater ( Fig. 19 A) (60 degrees); from S. (G.) yunnanense by the yellow hair tuft on the base of the radius (black hair tuft), and number of male upper-eye facets in 13 or 14 vertical columns (in 10 vertical columns).

The larva of this new species is characterized by the abdomen having grayish bands only on segments 1 and 2, faint head spots and medium-long postgenal cleft ( Fig. 20 C).

Figures

FIGURE 17. Female of Simulium (Gomphostilbia) unii sp. nov. A, Third segment of maxillary palp with sensory vesicle (right side; front view); B, Tip of mandible; C, Cibarium (front view); D, Hind tibia (left side; outer view); E, Hind basitarsus and second tarsomere (left side; outer view). F, Claw; G, Sternite 8 and ovipositor valve (right side only; ventral view); H, Genital fork (ventral view); I & J, Paraprocts and cerci (I, ventral view; J, lateral view). K, Spermatheca. Scale bars. 0.1 mm for D and E; 0.02 mm for A, C and G – K; 0.01 mm for B.

FIGURE 18. Male of Simulium (Gomphostilbia) unii sp. nov. A & B, Third segments of maxillary palps with sensory vesicles of different shape (A, right side; with ellipsoidal sensory vesicle; B, left side; with globular sensory vesicle; both front view); C, Hind tibia (left side; outer view); D, Hind basitarsus and second tarsomere (left side; outer view); E, Coxites, styles and ventral plate (ventral view); F, Style (right side; ventrolateral view); G, Ventral plate and median sclerite (lateral view); H, Ventral plate (caudal view); I, Median sclerite (caudal view); J, Paramere and aedeagal membrane (left side; caudal view); K & L, Abdominal segment 10 and cerci (right side; K, lateral view; L, caudal view). Scale bars. 0.1 mm for C and D; 0.02 mm for A, B and E – L.

FIGURE 19. Pupa of Simulium (Gomphostilbia) unii sp. nov. A, Anterior part of thorax and gill filaments (left side; outer view); B & C, Basal portions of gill filaments with different arrangements of dorsal and medial triplets (left side; outer view); D, Terminal hooks (caudal view); E & F, Cocoons (E, dorsal view; F, lateral view). Scale bars. 1.0 mm for E and F; 0.1 mm for A – C; 0.02 mm for D.

FIGURE 20. Larva of Simulium (Gomphostilbia) unii sp. nov. A, Mandible; B, Hypostoma; C, Head capsule (ventral view); D, Setae on dorsal surface of abdominal segment 8. Scale bars. 0.05 mm for C; 0.02 mm for B and D; 0.01 mm for A.