The black flies (Diptera: Simuliidae) of Vietnam Author Takaoka, Hiroyuki Author Sofian-Azirun, Mohd Author Ya’Cob, Zubaidah Author Chen, Chee Dhang Author Lau, Koon Weng Author Low, Van Lun Author Pham, Xuan Da Author Adler, Peter H. text Zootaxa 2017 4261 1 1 165 journal article 33106 10.5281/zenodo.571608 06d40acc-4fc2-4de6-9aab-96f3776ef44c 1175-5326 571608 C097C43E-D522-46C4-9D64-76D3CD4BAD86 Simulium ( Gomphostilbia ) quychauense Takaoka & Chen sp. nov. Male . Body length 2.3 mm . Head . Wider than thorax. Upper eye medium brown, consisting of large facets in 14 vertical columns and 14 horizontal rows. 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 longer hairs. Antenna composed of scape, pedicel and nine flagellomeres, dark brown except scape and pedicel yellow and base of first flagellomere whitish yellow; 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 1.0:1.2:2.5; third segment ( Fig. 13 A) slender; sensory vesicle ( Fig. 13 A) ellipsoidal, small (0.2 times length of third segment), and with small opening. Thorax . Scutum brownish black, shiny and thinly gray pruinose on prescutellar area when illuminated at certain angles, densely covered with golden-yellow scale-like recumbent short hairs. Scutellum dark brown, covered with yellow short hairs and dark-brown longer upright hairs. Postnotum brownish black, and white pruinose when illuminated at certain angles, and bare. Pleural membrane bare. Katepisternum dark brown, longer than deep, moderately covered with fine short hairs. Legs . Foreleg: coxa whitish yellow; trochanter light brown except base yellow; femur medium brown with apical cap dark brown (though apical tip yellowish); tibia light brown except little less than apical one-third brownish black, and outer surface paler medially, and covered with yellow hairs on basal two-thirds of outer surface; tarsus brownish black; basitarsus moderately dilated, 6.9 times as long as its greatest width. Midleg: coxa dark brown; trochanter light brown except base whitish yellow; femur light to medium brown with apical cap dark brown (though apical tip yellow); tibia brownish black except basal one-third whitish yellow; tarsus brownish black except base of basitarsus dark yellow (border not well defined). Hind leg: coxa medium brown; trochanter whitish yellow; femur medium brown with base narrowly whitish yellow and apical cap dark brown (though apical tip whitish yellow); tibia ( Fig. 13 B) medium to dark brown except basal two-fifths yellow, and apical cap brownish black; tarsus ( Fig. 13 C) medium brown except basal half of basitarsus grayish white (widely covered with dark hairs, thus border not well defined) and basal two-fifths of second tarsomere whitish; basitarsus ( Fig. 13 C) enlarged, 4.4 times as long as wide, and 0.9 and 0.8 times as wide as greatest width of tibia and femur, respectively; calcipala ( Fig. 13 C) as long as basal width, and 0.4 times as wide as greatest width of basitarsus. Pedisulcus ( Fig. 13 C) well developed. Wing . Length 1.9 mm . Costa with dark spinules and hairs except hairs on basal portion yellow. Subcosta without hairs. 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 outer surface and basal stem darkened. Abdomen . Basal scale dark brown, with fringe of dark hairs. Dorsal surface of abdomen medium to brownish black, covered with dark-brown short to long hairs; segments 2 and 5–7 each with pair of shiny dorsolateral or lateral patches; ventral surface of abdomen light to dark brown though segments 2–4 paler. Genitalia . Coxites, styles, ventral plate and median sclerite in ventral view as in Fig. 13 D. Coxite in ventral view ( Fig. 13 D) nearly rectangular, 1.8 times as long as its greatest width. Style in ventral view ( Fig. 13 D) bent inward, nearly parallel-sided, bluntly pointed apically and with apical spine; style in ventrolateral view ( Fig. 13 E) shorter than coxite (0.8 times length of coxite), 2.3 times as long as its greatest width at base, tapered to middle, then nearly parallel-sided and with round apex. Ventral plate in ventral view ( Fig. 13 D) with body transverse, 0.5 times as long as wide, with anterior margin produced anteromedially, and posterior margin appearing as flattened letter W, lateral margins somewhat emarginated basally, then slightly divergent posteriorly, and densely covered with microsetae on ventral surface; basal arms of moderate length, directed forward, then convergent apically; ventral plate in lateral view ( Fig. 13 F) moderately produced ventrally; ventral plate in caudal view ( Fig. 13 G) trapezoidal, with ventral margin nearly straight though slightly produced medially, densely covered with microsetae on posterior surface except portion near each lateral tip narrowly bare. Median sclerite ( Fig. 13 D, F, H) plate-like and wide. Parameres ( Fig. 13 I) of moderate size, each with four or five distinct long to short stout hooks. Aedeagal membrane ( Fig. 13 I) moderately setose; dorsal plate not defined. Ventral surface of abdominal segment 10 ( Fig. 13 J, K) weakly sclerotized anterolaterally and without distinct hairs near posterior margin. Cercus ( Fig. 13 J, K) small, rounded, with 13 or 14 hairs. FIGURE 13. Male of Simulium ( Gomphostilbia ) quychauense sp. nov. A, Third segment of maxillary palp with sensory vesicle; B, Hind tibia (left side; outer view); C, Hind basitarsus and second tarsomere (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 (caudal view); I, Paramere and aedeagal membrane (left side; caudal view); J & K, Abdominal segment 10 and cerci (left side; J, lateral view; K, caudal view). Scale bars. 0.1 mm for B and C; 0.02 mm for A and D–K. Pupa . Body length 2.4 mm . Head . Integument yellow, moderately and neatly covered with small round tubercles except antennal sheaths and ventral surface almost bare; antennal sheath without any protuberances; frons with three pairs of unbranched long trichomes with coiled or straight apices ( Fig. 14 A); face with pair of unbranched long trichomes with straight apices ( Fig. 14 B); 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 round tubercles except dorsolateral portion of posterior half sparsely covered, and with three long dorsomedial trichomes of different lengths (anterior trichome longest, posterior one shortest) with coiled apices ( Fig. 14 C), two long anterolateral trichomes with straight apices (anterior trichome more slender and slightly shorter than posterior one) ( Fig. 14 D), one medium-long mediolateral trichome with straight apex ( Fig. 14 E), and three ventrolateral trichomes with straight apices (one long, two short) ( Fig. 14 F) on each side; all trichomes unbranched. Gill ( Fig. 14 G) composed of eight slender thread-like filaments, arranged as [(2+1)+(1+2)]+2 from dorsal to ventral, with medium-long common basal stalk having somewhat swollen transparent basal fenestra at base; common basal stalk 0.8–0.9 times length of interspiracular trunk; dorsal and middle triplets sharing short stalk, and dorsal and middle triplets each composed of one individual and two paired filaments and bearing short to medium-long primary and short secondary stalks; stalk of ventral pair of filaments medium-long, 0.9–1.0 times length of common basal stalk, and 0.7–0.8 times length of interspiracular trunk, and 0.9 times as thick as common stalk of middle and dorsal triplets, 1.3 and 1.1 times as thick as stalks of dorsal and middle triplets, respectively; common stalk of dorsal and middle triplets as long as or shorter than primary stalks of dorsal and middle triplets; primary stalks of dorsal and middle triplets each much longer than secondary stalk; primary stalk of dorsal triplet lying against that of lower pair at angle of about 70 degrees when viewed laterally; all filaments damaged losing apical portion, thus no exact lengths known except one of middle triplet, which was intact and 1.9 mm long from base of common basal stalk to apical tip); six filaments of dorsal and middle triplets probably subequal in length and thickness to one another; two filaments of ventral pair probably subequal in length and thickness to each other (outer filament 2.5 mm from base of common basal stalk to broken tip), and 1.7 times as thick as six other filaments when compared basally; all filaments light brown, gradually tapered toward apex; cuticle of all filaments with moderately-defined annular ridges and furrows though becoming less marked apically, densely covered with minute tubercles. Abdomen . Dorsally, all segments light yellow and without tubercles; segment 1 with one unbranched slender medium-long hair-like seta ( Fig. 14 H) on each side; segment 2 with one unbranched slender medium-long hair-like seta and five minute setae ( Fig. 14 I) submedially on each side; segments 3 and 4 each with four hooked spines and one minute seta on each side; segment 5 with one spine ( Fig. 14 J) on right side and lacking spine-combs on left side; segments 6–8 each with spine-combs in transverse row and comb-like groups of minute spines on each side; segments 5–8 each with few minute setae near posterior margin on each side; segment 9 with comb-like groups of minute spines and pair of small terminal hooks ( Fig. 14 K, L). Ventrally, segment 4 with one unbranched hook (much smaller in size than those on segments 5–7) and few minute setae ( Fig. 14 M) on each side; segment 5 with pair of bifid hooks submedially and few 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 short slender setae on each side; segments 4–8 with comb-like groups of minute spines. Each side of segment 9 with three grapnel-shaped hooklets. Cocoon ( Fig. 14 N). Wall-pocket-shaped, thinly and moderately woven except anterolateral and peripheral portions roughly woven, widely extended ventrolaterally; dorsomedial portion of anterior margin slightly produced anteriorly; 3.0 mm long by 2.1 mm wide. Female and larva . Unknown. Type material . HOLOTYPE : Male (with its associated pupal exuviae) in 80% ethanol, labeled in a vial as [ UMSRP : Vietnam 0 26, Holotype , Simulium ( G .) quychauense , Male , coll. Vietnam , 11-XII-2015 , Takaoka et al .], reared from pupa collected from a small stream (width 1.5–3.0 m, bottom of pebbles and sands, water temperature 18 ˚C, exposed to the sun, elevation 73 m , 19˚30’45.487’’N/105˚09’09.261’’E), moderately flowing in a forest, Chau Dinh , Quy Chau , Nghe An Province , northern Vietnam , 11-XII-2015 , by H. Takaoka, M. Sofian-Azirun, C. D. Chen & K.W. Lau. Biological notes . The pupa of this new species was collected from a dead tree leaf. Associated species were S . ( G .) chaudinhense sp. nov. , S . ( S .) nodosum and S. ( S. ) tani (complex). Distribution. Vietnam ( Nghe An ). Etymology . The species name quychauense refers to the district name, Quy Chau , where this new species was collected. Remarks . This new species is assigned to the S. asakoae species-group of the subgenus Gomphostilbia by having the yellow hair tuft on the base of the radius, enlarged male hind basitarsi ( Fig. 13 C) and ventral plate with lateral margins emarginated basally ( Fig. 13 D). This new species is similar to S . ( G .) tamdaoense described from a male reared from a pupa in northern Vietnam ( Takaoka et al . 2014a ) in having the same number of male upper-eye (large) facets in 14 vertical columns and 14 horizontal rows, and relative size of the fore and hind basitarsi. It also is similar to S . ( G .) thituyenae described from a female reared from a pupa in southern Vietnam ( Takaoka et al. 2015a ) in having the small narrow pupal terminal hooks ( Fig. 14 L). However, this new species is distinguished from both species by the absence of the spine-combs on abdominal segment 9, and also from S . ( G .) tamdaoense by the absence of setae on the basal portion of the paramere ( Fig. 13 I) and small narrow pupal terminal hooks ( Fig. 14 L). FIGURE 14. Pupa of Simulium ( Gomphostilbia ) quychauense sp. nov. A, Frontal trichome; B, Facial trichome; C–F, Thoracic trichomes (C, anterodorsal; D, anterolateral; E, mediolateral; F, ventrolateral); G, Anterior part of thorax and gill filaments (left side; outer view); H, Hair-like seta on dorsal surface of abdominal segment 1; I, Hair-like seta and minute seta on dorsal surface of abdominal segment 2; J, Spine-comb on dorsal surface of abdominal segment 5; K & L, Terminal hooks (K, lateral view; L, caudal view); M, Hooklet and minute seta on ventral surface of abdominal segment 4; N, Cocoon (dorsal view). Scale bars. 1.0 mm for N; 0.1 mm for G; 0.02 mm for A–F, H, I, K and L; 0.01 mm for J and M. Simulium ( Gomphostilbia ) sanchayense Takaoka & Lau sp. nov. Simulium ( Gomphostilbia ) brinchangense : not Takaoka, Sofian-Azirun & Hashim (in Takaoka et al ., 2014a ): 364–365. This species was previously reported from Vietnam as S . ( G .) brinchangense Takaoka, Sofian-Azirun & Hashim , originally described from Peninsular Malaysia ( Takaoka et al . 2014a , d ). A DNA sequence-based analysis using the COI gene shows that this species is distinct from S . ( G .) brinchangense (Low et al . unpublished data). This species is here described as a new species although our morphological reexamination of the males and their associated pupal exuviae collected from Tam Dao, Vinh Phuc Province , reveals that they are almost identical to those of S . ( G .) brinchangense except for a few morphological features as noted later. Male . Body length 2.9 mm . Head . Nearly as wide as thorax. Upper eye medium brown, consisting of large facets in 12 vertical columns and 14 horizontal rows. Face brownish black, white pruinose. Clypeus brownish black, whitish pruinose, moderately covered with golden-yellow scale-like medium-long hairs (mostly directed upward) interspersed with several dark-brown longer hairs. Antenna composed of scape, pedicel and nine flagellomeres, medium brown except scape and pedicel yellow and base of first flagellomere whitish yellow; first flagellomere elongate, 1.75 times length of second one. Maxillary palp light to medium brown, with five segments, proportional lengths of third, fourth, and fifth segments 1.0:1.2:2.9; third segment ( Fig. 15 A) slender, somewhat produced posteromedially; sensory vesicle ( Fig. 15 A) ellipsoidal, small (0.2 times length of third segment), and with opening of medium-size. Thorax . Scutum brownish black except anterolateral calli medium brown, shiny and thinly gray pruinose on shoulders, on wide area along each lateral margin and on prescutellar area when illuminated at certain angles, densely covered with golden-yellow scale-like recumbent short hairs. Scutellum light brown, covered with yellow short hairs and dark-brown longer upright hairs along posterior margin. Postnotum brownish black, shiny and white pruinose when illuminated at certain angles, and bare. Pleural membrane bare. Katepisternum dark brown, longer than deep, shiny when illuminated at certain angles, moderately covered with fine short hairs. Legs . Foreleg: coxa whitish yellow; trochanter light brown except base yellow; femur light brown with apical cap medium brown (though apical tip yellowish); tibia white to grayish except little less than apical one-third brownish black, and covered with white and yellow hairs on basal two-thirds of outer surface and white sheen on basal two-thirds of outer surface when illuminated at certain angles; tarsus brownish black; basitarsus moderately dilated, 8.0 times as long as its greatest width. Midleg: coxa medium brown except posterior surface dark brown; trochanter light brown except base whitish yellow; femur light brown with apical cap medium brown (though apical tip yellow); tibia medium brown except basal one-third whitish yellow; tarsus dark brown except basal half of basitarsus dark yellow to light brown (border in middle not well defined). Hind leg: coxa light brown though apical portion whitish yellow; trochanter whitish yellow; femur light brown with base narrowly whitish yellow and apical cap dark brown (though apical tip whitish yellow); tibia ( Fig. 15 B) dark brown to brownish black except little less than basal half whitish yellow; tarsus ( Fig. 15 C) medium to dark brown except little less than basal half of basitarsus and basal half of second tarsomere yellowish; basitarsus ( Fig. 15 C) enlarged, 3.5 times as long as wide, and 1.0 and 1.2 times as wide as greatest width of tibia and femur, respectively; calcipala ( Fig. 15 C) slightly shorter than basal width, and 0.3 times as wide as greatest width of basitarsus. Pedisulcus ( Fig. 15 C) well developed. Wing . Length 2.1 mm . Costa with dark spinules and hairs except hairs on basal portion yellow. Subcosta with two to four hairs. 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 stem darkened. Abdomen . Basal scale dark brown, with fringe of dark hairs. Dorsal surface of abdomen medium to dark brown, covered with dark-brown short to long hairs; segments 2 and 5–7 each with pair of shiny dorsolateral or lateral patches; ventral surface of abdomen light to dark brown except segments 2 and 3 pale. Genitalia . Coxites, styles and ventral plate in ventral view as in Fig. 15 D. Coxite in ventral view ( Fig. 15 D) nearly rectangular, 1.91 times as long as its greatest width. Style in ventral view ( Fig. 15 D) bent inward, nearly parallel-sided, bluntly pointed apically and with apical spine; style in ventrolateral view ( Fig. 15 E) shorter than coxite (0.8 times length of coxite), 2.1 times as long as its greatest width at base, slightly tapered to apex, and with truncated apex. Ventral plate in ventral view ( Fig. 15 D) 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), lateral margins slightly emarginated near base, and densely covered with microsetae on ventral surface; basal arms of moderate length, slightly divergent, then convergent apically; ventral plate in lateral view ( Fig. 15 F) moderately produced ventrally; ventral plate in caudal view ( Fig. 15 G) trapezoidal, with ventral margin nearly straight though slightly produced medially, densely covered with microsetae on posterior surface except portion near each lateral tip narrowly bare. FIGURE 15. Male of Simulium ( Gomphostilbia ) sanchayense sp. nov. A, Third segment of maxillary palp with sensory vesicle (left side; front view); B, Hind tibia (left side; outer view); C, Hind basitarsus and second tarsomere (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 (caudal view); I, Paramere and aedeagal membrane (left side; caudal view); J & K, Abdominal segment 10 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. Median sclerite ( Fig. 15 H) plate-like and wide. Parameres ( Fig. 15 I) of moderate size, each with four distinct long and medium-long stout hooks and several smaller ones including smallest ones on middle part of basal arm. Aedeagal membrane ( Fig. 15 I) moderately setose; dorsal plate not defined. Ventral surface of abdominal segment 10 ( Fig. 15 J, K) weakly sclerotized anteriorly and without distinct hairs near posterior margin. Cercus ( Fig. 15 J, K) small, rounded, with 11 or 12 hairs. Pupa . Body length 2.4 mm . Head . Integument yellow, moderately covered with small round tubercles except antennal sheaths and ventral surface almost bare; antennal sheath without any protuberances; frons with three pairs of unbranched long trichomes with coiled apices ( Fig. 16 A); face with pair of unbranched long trichomes with coiled apices ( Fig. 16 B); three frontal trichomes on each side arising close together, subequal in length to one another and slightly longer than facial one. Thorax . Integument yellow, moderately covered with round tubercles, and with three long dorsomedial trichomes of different lengths (anterior trichome longest, posterior one shortest) with coiled apices ( Fig. 16 C), two long anterolateral trichomes (anterior trichome shorter and more slender than posterior one and with straight apex, and posterior one with coiled apex) ( Fig. 16 D), one medium-long mediolateral trichome with straight apex ( Fig. 16 E), and three ventrolateral trichomes (one medium-long and two short) with straight apices ( Fig. 16 F) on each side; all trichomes unbranched. Gill ( Fig. 16 G) composed of eight slender threadlike filaments, arranged as [3+(1+2)]+2 from dorsal to ventral, with medium-long common basal stalk having somewhat swollen transparent basal fenestra at base; common basal stalk 0.65–0.76 times length of interspiracular trunk; dorsal and middle triplets sharing short stalk, and dorsal triplet composed of three individual filaments arising at same level, with short stalk, middle triplet composed of one individual and two paired filaments and bearing short primary and secondary stalks; stalk of ventral pair of filaments medium-long, 1.2–1.6 times length of common basal stalk, and 0.9 times length of interspiracular trunk, and 0.9–1.0 times as thick as common stalk of middle and dorsal triplets; common stalk of dorsal and middle triplets 0.7–1.3 and 0.5–1.0 times lengths of primary stalks of dorsal and middle triplets, respectively; middle triplet primary stalk 1.3–9.3 times length of secondary stalk; primary stalk of dorsal triplet lying against that of lower pair at angle of 60–80 degrees when viewed laterally; six filaments of dorsal and middle triplets subequal in length ( 1.9–2.2 mm ) and thickness to one another; two filaments of ventral pair subequal in length (3.0 mm) and thickness to each other, and 1.4 times as thick as six other filaments when compared basally; all filaments light brown, gradually tapered toward apex; cuticle of all filaments with well-defined annular ridges and furrows though becoming less marked apically, densely covered with minute tubercles. Abdomen . Dorsally, all segments unpigmented and without tubercles; segment 1 with one unbranched slender short hair-like seta (similar to Fig. 16 H) on each side; segment 2 with one unbranched slender short hair-like seta and five somewhat spinous minute setae ( Fig. 16 H) submedially on each side; segments 3 and 4 each with four hooked spines and one somewhat spinous minute seta on each side; segment 5 lacking spine-combs and comb-like groups of minute spines on each side; segments 6–9 each with spine-combs in transverse row and comb-like groups of minute spines on each side; segments 5–8 each with few minute setae near posterior margin on each side; segment 9 with pair of wide flat terminal hooks, of which outer margin is 2.6–3.2 times length of inner margin and crenulated ( Fig. 16 I) when viewed caudally. Ventrally, segment 4 with one unbranched hook (subequal in size to those on segments 5–7) and few slender short setae on each side; segment 5 with pair of bifid hooks submedially and few 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 short slender setae on each side; segments 4–8 each with comb-like groups of minute spines. Each side of segment 9 with three grapnel-shaped hooklets. Cocoon ( Fig. 16 J, K). Wall-pocket-shaped, thinly and moderately woven, widely extended ventrolaterally; dorsomedial portion of anterior margin slightly to somewhat produced anteriorly; 3.0– 3.1 mm long by 2.0– 2.2 mm wide. Female and larva . Unknown. Type material . HOLOTYPE : Male (with its associated pupal exuviae and cocoon) in 80% ethanol, labeled in a vial as [ UMSRP : Vietnam 0 27, Holotype , Simulium ( G .) sanchayense , Male , coll. Vietnam , 8-XI-2013 , Takaoka et al. ], reared from a pupa collected from a small stream (width 0.5 m , bottom rocky, water temperature 17˚C, shaded, elevation 975 m , 21˚27’501’’N/105˚38’941’’E), slow-flowing in bushes along the road near the Tam Dao National Park , Vinh Phuc Province , northern Vietnam , 8-XI-2013 , by H. Takaoka, M. Sofian-Azirun & Z. Ya’cob. PARATYPES : Two males (with their associated pupal exuviae and cocoons) in 80% ethanol, same data as those of the holotype , labeled in each vial as [ UMSRP : Vietnam 0 27, Paratype , Simulium ( G .) sanchayense , Male , coll. Vietnam , 8-XI-2013 , Takaoka et al. ]. FIGURE 16. Pupa of Simulium ( Gomphostilbia ) sanchayense sp. nov. A, Frontal trichome; B, Facial trichome; C–F, Thoracic trichomes (C, anterodorsal; D, anterolateral; E, mediolateral; F, ventrolateral); G, Anterior part of thorax and gill filaments (left side; outer view); H, Hair-like seta and minute seta on dorsal surface of abdominal segment 2; I, Terminal hooks (caudal view); J & K, Cocoons with slightly different anterodorsal margins (dorsal view). Scale bars. 1.0 mm for J and K; 0.1 mm for G; 0.02 mm for A–F, H and I. Biological notes . The pupae of this new species were collected from dead tree leaves. The associated species were S . ( G .) hongthaii , S . ( G .) vinhphucense sp. nov. , S . ( N. ) sp. ( Simulium feuerborni species-group) and S . ( S .) lowi sp. nov. Distribution. Vietnam ( Vinh Phuc ). Etymology . The species name sanchayense refers to the land in which the San Chay tribe lives. Remarks . This new species is assigned to the S. asakoae species-group of the subgenus Gomphostilbia by having the yellow hair tuft on the base of the radius, enlarged male hind basitarsi ( Fig. 15 C) and ventral plate with lateral margins emarginated ( Fig. 15 D). The male of this new species is almost identical to that of S . ( G .) brinchangense , including the moderate number of upper-eye (large) facets in 12 vertical columns and 14 horizontal rows and color of the legs ( Takaoka et al . 2014d ). There are slight differences in some male features between this new species and S . ( G .) brinchangense (characters of S . ( G .) brinchangense in parentheses): length ratio of the first flagellomere of the antenna against the second one is 1.8 (1.9), length ratio of the hind basitarsus against its greatest width is 3.5 (3.7–3.8), ventral margin of the ventral plate is nearly straight when viewed posteriorly (concave). The pupa of this new species is almost identical to that of S . ( G .) brinchangense except that the middle triplet of the gill is composed of one individual and two paired filaments ( Fig. 16 G) (three filaments arising at the same level in S . ( G .) brinchangense ) and the dorsal triplet of the gill is composed of three filaments arising at the same level ( Fig. 16 G) (one individual and two paired filaments in S . ( G .) brinchangense ).