Simulium (Gomphostilbia) thungchangense Takaoka, Srisuka & Saeung, 2020

Takaoka, Hiroyuki, Srisuka, Wichai, Fukuda, Masako & Saeung, Atiporn, 2020, Twenty-one new species of the Simulium (Gomphostilbia) asakoae species group (Diptera, Simuliidae) in Thailand, with their genetic relationships, ZooKeys 950, pp. 51-152 : 51

Simulium (Gomphostilbia) thungchangense Takaoka, Srisuka & Saeung sp. nov. Figs 1 , 2 , 3 , 25Q

Material examined.

Holotype: Male (with its associated pupal exuviae and cocoon) (in 80% ethanol) labeled as "Holotype: Simulium thungchangense male, QSBG col. no. 8, Thailand, 24-I-2019, by W. Srisuka", collected from a stream (width 60 cm, depth 10 cm, bed sandy, moderate flow, pH 6.9, 17.9 °C, exposed to the sun, elevation 1,376 m, 18°32'44.4"N, 98°30'53.0"E), at Siribhum waterfall, Chom thong District, Chiang Mai Province, Thailand, 24-I-2019, by W. Srisuka (Coll. No. 8).

Paratypes: 10 females, 10 males (one male for DNA analysis) (with their associated pupal exuviae and cocoons), and 20 mature larvae (two mature larvae for DNA analysis) (in 80% ethanol), same data as for holotype; one male (with its associated pupal exuviae and cocoon) and one pharate male (with its associated pupal exuviae and cocoon) (in 80% ethanol), collected from a stream (18 °C, elevation 1,470 m) from Phu Kha, Samorrophum, Thung Chang District, Nan Province, 2-XII-2004, by W. Choochote.

Diagnosis.

Female: mandible with several teeth on the outer margin and hind tibia yellowish on little more than the basal half (Fig. 1E ). Male: small number of upper-eye facets in nine vertical columns and 12 horizontal rows, presence of many hairs on the subcosta and much widened hind basitarsus 1.5-1.7 times as wide as the hind femur. Pupa: dorsal surface of abdominal segments 1 and 2 sparsely covered with minute tubercles. Larva: postgenal cleft as long as or little longer than the postgenal bridge (Fig. 3F ) and abdominal segments 1-4 light greenish or greenish grey (Fig. 25Q ).

Description.

Female (N = 10). Body length 2.5-2.6 mm.

Head. Slightly narrower than width of thorax. Frons dark brown, densely covered with yellowish white scale-like recumbent short hairs interspersed with few dark longer hairs near vertex; frontal ratio 1.8-1.9:1.0:2.5-2.6; frons:head ratio 1.0:4.2-4.7. Fronto-ocular area well developed, narrow, directed dorsolaterally. Clypeus dark brown, densely covered with yellowish white scale-like hairs interspersed with several dark longer hairs on each side. Labrum 0.62-0.68 times length of clypeus. Antenna composed of scape, pedicel and nine flagellomeres, dark brown except scape, pedicel and base of first flagellomere yellow. Maxillary palpus composed of five palpomeres, light to medium brown, proportional lengths of third, fourth, and fifth palpal segments 1.0:1.1:2.6; sensory vesicle (Fig. 1A ) ellipsoidal, medium-long (0.33-0.38 times length of third palpal segment), with medium-sized opening. Lacinia with 10-12 inner and 12-16 outer teeth. Mandible with 23-26 inner teeth and five to eight outer teeth at some distance from tip. Cibarium (Fig. 1B ) medially forming sclerotized plate folded forward from posterior margin, with weakly sclerotized mediolongitudinal ridge with dark bifid apex.

Thorax. Scutum dark brown except anterolateral calli ochreous, and three blackish longitudinal vittae (one median, two submedian) faintly visible, thinly pruinose and shiny when illuminated at certain angles, densely covered with 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 when illuminated at certain angles, and bare. Pleural membrane ochreous and bare. Katepisternum longer than deep, medium to dark brown, shiny when illuminated at certain angles, moderately covered with fine yellow and brown short hairs.

Legs. Foreleg: coxa and trochanter whitish yellow; femur dark yellow to light brown with apical cap medium brown (though extreme tip yellowish); tibia yellowish white except apical one-fourth brownish black and covered with white fine hairs on basal four-fifths; tarsus brownish black, with moderate dorsal hair crest; basitarsus moderately dilated, 6.6-6.9 times as long as its greatest width. Midleg: coxa medium brown except posterolateral surface dark brown; trochanter whitish yellow; femur light to medium brown with basal one-fourth whitish yellow and apical cap medium brown (though extreme tip yellowish); tibia whitish yellow on basal two-fifths and light to dark brown on rest (though whitish yellow on basal half or little more on posterior surface in some females), and covered with yellowish fine hairs on posterior and inner surfaces of basal two-thirds; tarsus dark brown to brownish black though basal one-third of basitarsus dark yellow (its border not well defined). Hind leg: coxa medium brown with apical one-third yellow; trochanter whitish yellow; femur medium brown with base whitish yellow and apical cap dark brown (though extreme tip yellowish white); tibia (Fig. 1C ) yellowish white on basal half and light brown to 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 (though base light brown) and basal half of second tarsomere yellowish white; basitarsus (Fig. 1D ) narrow, nearly parallel-sided, though slightly narrowed apically, 5.9-6.4 times as long as wide, and 0.7-0.8 and 0.6 times as wide as greatest widths of tibia and femur, respectively; calcipala (Fig. 1D ) nearly as long as width at base, and 0.5 times as wide as greatest width of basitarsus; pedisulcus (Fig. 1D ) well developed; claw (Fig. 1E ) with large basal tooth 0.5 times length of claw.

Wing. Length 2.2-2.4 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 ochreous, with fringe of whitish yellow hairs. Dorsal surface of abdomen medium to dark brown except anterior half of segment 2 ochreous, moderately covered with dark short to long hairs; tergites of segments 2 and 6-9 shiny when illuminated at certain angles. Ventral surface of segments 2-4 yellow and those of other segments medium to dark brown; sternal plate on segment 7 undeveloped.

Terminalia. Sternite 8 (Fig. 1F ) bare medially, with 19 or 20 medium-long to long hairs together with three or four slender short hairs on each side. Ovipositor valves (Fig. 1F ) tongue-like, thin, membranous, each moderately covered with microsetae interspersed with one or two short hairs; inner margins slightly concave medially, somewhat sclerotized, and moderately separated from each other. Genital fork (Fig. 1G ) of usual inverted-Y form, with slender stem; arms of moderate width, moderately folded medially. Paraproct in ventral view (Fig. 1H ) somewhat concave anterolaterally, with five or six sensilla on anteromedial surface; paraproct in lateral view (Fig. 1I ) somewhat produced ventrally beyond ventral tip of cercus, 0.6-0.7 times as long as wide, with 22-25 medium-long to long hairs on ventral and lateral surfaces. Cercus in lateral view (Fig. 1I ) short, slightly rounded posteriorly, 0.4 times as long as wide. Spermatheca (Fig. 1J ) ellipsoidal, 1.4 times as long as its greatest width, well sclerotized and darkened except duct and small area near juncture with duct unpigmented, and with many fissures on outer surface; internal setae absent; both accessory ducts slender, subequal in diameter to major one.

Male (N = 14). Body length 2.6-3.1 mm.

Head. Nearly as wide as thorax. Upper eye vermilion, consisting of large facets in 9 (rarely 10) vertical columns and 12 horizontal rows on each side. Clypeus brownish black, whitish pruinose, densely covered with golden-yellow scale-like medium-long hairs (mostly directed upward) interspersed with several dark-brown simple longer hairs near lower margin. Antenna composed of scape, pedicel and nine flagellomeres, medium to dark brown except scape, pedicel, and base of first flagellomere yellow; first flagellomere elongate, 1.8 times length of second. Maxillary palpus light brown, with five palpal segments, proportional lengths of third, fourth, and fifth palpomeres 1.0:1.1-1.2:2.7-3.0; third palpomere (Fig. 2A ) slender; sensory vesicle (Fig. 2A ) small, ellipsoidal (0.18-0.24 times length of third palpal segment), and with small opening.

Thorax. Scutum dark brown to brownish black except anterolateral calli ochreous, shiny and white pruinose when illuminated at certain angles, and densely covered with whitish yellow scale-like recumbent short hairs. Scutellum dark brown, covered with yellow short hairs and dark-brown long upright hairs along posterior margin. Postnotum brownish black, slightly shiny and white pruinose when illuminated at certain angles, and bare. Pleural membrane ochreous and bare. Katepisternum dark brown, longer than deep, shiny and white pruinose when illuminated at certain angles, moderately covered with yellow and brown fine short hairs.

Legs. Foreleg: coxa whitish yellow; trochanter light brown; femur light brown except apical tip yellowish; tibia whitish yellow except little more than apical one-third dark brown, and covered with white hairs on whitish yellow portion; tarsus brownish black; basitarsus slightly dilated, 8.4-8.7 times as long as its greatest width. Midleg: coxa dark brown except posterolateral surface brownish black; trochanter dark yellow to light brown except base yellow; femur light to medium brown with base yellowish and apical cap dark brown (though apical tip yellow); tibia dark brown except basal one-third (or little more on posterior surface) whitish yellow; tarsus dark brown except basal one-fourth or less of basitarsus dark yellow to light brown (border not well defined). Hind leg: coxa dark brown; trochanter yellowish; femur medium to dark brown with base yellow and apical cap brownish black (though apical tip yellow); tibia dark brown to brownish black except little more than basal two-fifths whitish yellow; tarsus (Fig. 2B ) brownish black except basal two-fifths of basitarsus and little less than basal half of second tarsomere whitish yellow; basitarsus (Fig. 2B ) enlarged, 3.3-3.7 times as long as wide, and 1.1-1.2 and 1.5-1.7 times as wide as greatest width of tibia and femur, respectively; calcipala (Fig. 2B ) slightly shorter than basal width, and 0.23 times as wide as greatest width of basitarsus; pedisulcus (Fig. 2B ) well developed.

Wing. Length 2.2-2.4 mm. Other characters as in female except subcosta with 9-13 hairs. Halter. Dull white except basal stem darkened.

Abdomen. Basal scale dark brown, with fringe of light-brown hairs. Dorsal surface of abdomen medium brown to brownish black, covered with dark brown short to long hairs except segment 2 with yellowish hairs; segments 2 and 5-8 each with pair of shiny dorsolateral or lateral patches; ventral surface of segment 2 yellow, those of segments 3 and 4 yellow though sternal plates light brown, and those of other segments medium to dark brown.

Genitalia. Coxite in ventral view (Fig. 2C ) nearly rectangular, 1.7 times as long as its greatest width. Style in ventral view (Fig. 2C ) bent inward, with triangular apex having single spine; style in ventrolateral view (Fig. 2D ) slightly tapered toward apex, with truncated apex. Ventral plate in ventral view (Fig. 2C ) with body transverse, 0.6 times as long as wide, with anterior margin produced anteromedially, posterior margin somewhat concave medially, and lateral margin emarginated medially, and densely covered with microsetae on ventral surface; basal arms of moderate length, slightly divergent, then convergent apically; ventral plate in lateral view (Fig. 2E ) moderately produced ventrally; ventral plate in caudal view (Fig. 2F ) rounded ventrally, densely covered with microsetae on posterior surface. Median sclerite (Fig. 2G ) plate-like, wide. Parameres (Fig. 2H ) 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. 2H ) moderately setose; dorsal plate not defined. Ventral surface of abdominal segment 10 (Fig. 2I, J ) slightly sclerotized along anterior margin and without distinct hairs near posterolateral corners. Cercus (Fig. 2I, J ) small, rounded, with 12-17 hairs.

Pupa (N = 24). Body length 2.5-3.3 mm.

Head. Integument deep 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 or without coiled apices; face with pair of unbranched (rarely bifid) long trichomes with straight apices; three frontal trichomes on each side arising close together, subequal in length to one another and slightly longer than facial one.

Thorax. Integument deep yellow, moderately covered with round tubercles, and with three long dorsomedial trichomes with coiled apices, two long anterolateral trichomes (anterior trichome more slender and shorter with straight or coiled apex, posterior one with coiled apex), one medium-long mediolateral trichome with straight apex, and three ventrolateral trichomes (one medium-long, two short) with straight apices, on each side; all trichomes unbranched. Gill (Fig. 3A ) composed of eight slender thread-like filaments, arranged as [3+(1+2)]+2 (or rarely [(2+1)+(1+2)]+2 or [(2+1)+3]+2) from dorsal to ventral, with medium-long common basal stalk having somewhat swollen transparent basal fenestra at base; common basal stalk 0.7-0.8 times length of interspiracular trunk; dorsal and middle triplets sharing short stalk, and dorsal triplet mostly composed of three individual filaments arising at same level, middle triplet typically composed of one individual and two paired filaments with extremely short secondary stalk; stalk of ventral pair of filaments variable in length, 0.7-1.6 times length of common basal stalk, and 0.6-1.1 times length of interspiracular trunk, and 0.9 times as thick as common stalk of middle and dorsal triplets; primary stalk of dorsal triplet lying against that of lower pair at angle of 60-90° when viewed laterally; filaments of dorsal and middle triplets subequal in length (2.2-2.7 mm) and thickness to one another; two filaments of ventral pair subequal in length (3.0-3.4 mm) and thickness to each other and 1.3 times as thick as six other filaments of dorsal and middle triplets when compared basally; all filaments yellow to 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 or light yellowish except segment 9 and bases of spine-combs of segments 6-8 yellow; segments 1 and 2 sparsely covered with minute tubercles; segment 1 with one unbranched slender short hair-like seta on each side; segment 2 with one unbranched slender short hair-like seta and five somewhat spinous minute setae 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 micro-spines on each side; segment 5 with four minute setae on each side; segments 6-8 each with two minute setae on each side; segment 9 with pair of wide flat terminal hooks (Fig. 3B ), of which outer margin 2.7 times length of inner margin and crenulated when viewed caudally. Ventrally, segment 4 with one unbranched hook (subequal in size to those on segments 5-7) and few slender short setae, of which one is much longer and stouter, on each side; segment 5 with pair of bifid or trifid 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 micro-spines. Each side of segment 9 with three grapnel-shaped hooklets.

Cocoon (Fig. 3C ). Slipper-shaped, roughly to moderately woven, widely extended ventrolaterally; anterior margin thickly woven medially, often with bulge or short projection; posterior three-fifths with floor roughly woven; individual threads visible; 3.4-4.2 mm long by 2.2-3.5 mm wide.

Mature larva (N = 20). Body length 5.5-6.5 mm. Body creamy white to light ochreous with following color markings: thoracic segment 1 encircled with distinct ochreous band (though disconnected ventromedially), thoracic segments 2 and 3 ochreous on ventral surface; abdominal segments 1-4 entirely light green or greenish grey, abdominal segment 4 with reddish brown transverse band (though often partially faded, leaving narrow band or small spot(s) dorsally), abdominal segment 5 with distinct reddish brown, W-shaped, transverse band dorsally, abdominal segment 6 often with three distinct, reddish brown spots (one round dorsomedial spot and two lateral spots of various size and shape), dorsal and dorsolateral surface of abdominal segments 5-8 faintly to distinctly covered with pinkish pigment (Fig. 25Q ).

Head. Head capsule yellow to dark yellow except eye-spot region whitish, sparsely covered with minute setae (though moderately on dorsal surface); head spots faintly positive or indistinct. Antenna composed of three articles and apical sensillum, longer than stem of labral fan; proportional lengths of first, second, and third articles 1.0:0.8:0.7. Labral fan with 29-31 primary rays. Mandible (Fig. 3D ) 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° against mandible on apical side; supernumerary serrations absent. Hypostoma (Fig. 3E ) with row of nine apical teeth, of which median tooth little longer than each corner tooth; lateral margin smooth; four or five hypostomal bristles per side lying nearly parallel to lateral margin. Postgenal cleft (Fig. 3F ) small, rounded, 1.0-1.2 times length of postgenal bridge. Cervical sclerites composed of pair of small yellow rod-like pieces.

Thorax and abdomen. Cuticle sparsely covered with unpigmented minute setae (though few posterior abdominal segments sparsely covered also with dark minute unbranched setae) dorsally; 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. Rectal scales minute, unpigmented. Rectal organ compound, each of three lobes with seven or eight finger-like secondary lobules. Anal sclerite of usual X-form, with anterior arms 1.2 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 80-86 rows of hooklets with up to 14 or 15 hooklets per row.

Etymology.

The species name, thungchangense , refers to the district, Thung Chang, one of the two localities where this species was collected.

Distribution.

Thailand (Chiang Mai and Nan).

Discussion.

This new species is similar to S. chaudinhense Takaoka & Sofian-Azirun described from Vietnam ( Takaoka et al. 2017a) in many characters including the presence of teeth on the outer margin of the female mandible, small number of male upper-eye facets, and pupal abdominal segments 1 and 2 each with small tubercles on the dorsal surface. However, it is distinguished from the latter species by the male hind basitarsus 1.5-1.7 times as wide as the hind femur, and larval abdominal segments 1-4 light green or greenish grey (Fig. 25Q ) (in S. chaudinhense , the male hind basitarsus is 1.2-1.3 times as wide as the hind femur and larval abdominal segments 1 and 2 are greyish).

Figures

Figure 1. Female of S. thungchangense sp. nov. A third palpal segment with sensory vesicle (right side; anterior view) B cibarium (anterior view) C hind tibia (left side; lateral view) D hind basitarsus and second tarsomere (left side; lateral view) E claw F sternite 8 and ovipositor valves (ventral view) G genital fork (ventral view) H, I paraprocts and cerci (right side H ventral view I lateral view) J spermatheca. Scale bars: 0.1 mm (C, D); 0.02 mm (A, B, F-J); 0.01 mm (E).

Figure 2. Male of S. thungchangense sp. nov. A sensory vesicle (right side; anterior view) B hind basitarsus and second tarsomere (left side; lateral view) C coxites, styles and ventral plate (ventral view) D style (right side; ventrolateral view) E ventral plate and median sclerite (lateral view) F ventral plate (caudal view) G median sclerite (caudal view) H paramere and aedeagal membrane (right half; caudal view) I, J tenth abdominal segments and cerci (right side I lateral view J caudal view). Scale bars: 0.1 mm (B); 0.02 mm (A, C-J).

Figure 3. Pupa and larva of S. thungchangense sp. nov. A-C pupa D-F larva. A gill filaments (left side; lateral view) B terminal hooks (caudal view) C cocoon (dorsal view) D mandible E hypostoma F head capsule (ventral view). Scale bars: 1.0 mm (C); 0.1 mm (A, F); 0.02 mm (E); 0.01 mm for (B, D).

Figure 25. Schematic illustrations of larval body color patterns (dorsal view). A S. teerachanense sp. nov. B S. pitasawatae sp. nov. C S. sutheppuiense sp. nov. D S. asakoae E S. klonglanense sp. nov. F S. namdanense sp. nov. G S. chaowaense sp. nov. H S. loeiense sp. nov. I S. huaimorense sp. nov. J S. nanoiense sp. nov. K S. junkumae sp. nov. L S. myanmarense M S. maewongense sp. nov. N S. phapeungense sp. nov. O S. muangpanense sp. nov. P S. maehongsonense sp. nov. Q S. thungchangense sp. nov. R S. chiangdaoense S S. inthanonense (morph 1) T S. inthanonense (morph 2).