Simulium (Gomphostilbia) krishnani Anbalagan & Vijayan & Balachandran & Thiyonila & Surya 2020, sp. nov.

Simulium (Gomphostilbia) krishnani sp. nov.

(Figs 4–6)

(Zoobank Ref. No: urn:lsid:zoobank.org:pub: 88E6EA69-35D2-4DC8-85BA-E1C9EEBB0E55)

Diagnosis. Female: scutum with 3 brownish-black longitudinal vittae, hind basitarsus 7.64 times as long as wide, the subbasal tooth 0.68 times as long as tarsal claw and spermatheca 1.28 times as long as its greatest width. Male: small sensory vesicle (0.21 times as long as 3 rd segment) and hind basitarsus 4.4 times as long as wide. Pupa: respiratory gill with 8 filaments and stalk of ventral pair 0.94–0.95 times as thick as primary stalk of middle triplet. Larva: labral fan with 28 main rays, postgenal cleft 3.0 times as long as postgenal bridge and posterior circlet with 64 rows of hooklets.

Description. Female. Body length 1.8 mm. Head. Narrower than width of thorax. Frons black, shiny when illuminated at certain angles, thinly yellowish pruinose, with several stout dark hairs along lateral and lower margins; frontal ratio 1.3:1.0:1.5; frons-head ratio 1.0:2.61. Fronto-ocular area well developed, narrow, directed dorsolaterally. Antenna composed of scape, pedicel and 9 flagellomeres, brown except scape, pedicel and basal 0.5 of 1 st flagellomere yellow. Clypeus grayish-black, slightly shiny when illuminated at certain angles, densely covered with yellow hairs interspersed with several dark longer hairs on each side. Labrum 0.7 times as long as clypeus. Maxillary palp composed of 5 segments; proportional lengths of 3 rd, 4 th and 5 th segments 1.0:0.8:1.2; 3 rd segment (Fig. 4A) moderately enlarged; sensory vesicle (Fig. 4A) medium-sized (0.35 times as long as 3 rd segment), with medium-sized round opening. Maxillary lacinia with 6 inner and 12 outer teeth. Mandible with 24 inner teeth and lacking outer teeth though outer margin with several very low round ridges at some distance from apex. Cibarium (Fig. 4B) medially forming sclerotized plate folded forward from posterior margin, with moderately sclerotized mediolongitudinal ridge. Thorax. Scutum dark brown except anterolateral calli dark ochreous, with 3 brownish-black longitudinal vittae (1 narrow median and 2 lateral), median vitta united anteriorly to anterior calli, lateral vittae united posteriorly to prescutellar area; scutum shiny when illuminated at certain angles, densely covered with yellow scale-like recumbent shorthairs interspersed with dark brown long upright hairs on prescutellar area. Scutellum shiny, with dark brown short hairs. Postnotum shiny and bare. Pleural membrane bare. Katepisternum medium to dark brown, longer than deep, shiny when illuminated at certain angles, densely covered with fine short hairs. Legs. Foreleg: coxa yellow; trochanter yellow except apical portion somewhat darkened; femur light brown; tibia brown; tarsus brownish black, with moderate dorsal hair crest; basitarsus slightly dilated, 5.3 times as long as its greatest width. Midleg: coxa yellowish brown except posterior surface dark brown; trochanter yellow to light brown; femur and tibia brown; tarsus brownish-black except basal 1/2 of basitarsus dark yellow. Hind leg: coxa yellowish brown; trochanter yellow; femur medium brown with base yellow and apical cap dark brown; tibia light to dark brown with basal 1/6 white, covered with brownish fine hairs on outer and posterior surfaces; tarsus brownish-black except basal 2/3 of basitarsus (though base light brown); basitarsus (Fig. 4C) narrow, nearly parallel-sided, 7.64 times as long as wide, and 0.54 and 0.46 times as wide as greatest width of tibia and femur, respectively; calcipala (Fig. 4C) slightly shorter than width at base, and 0.55 times as wide as greatest width of basitarsus. Pedisulcus (Fig. 4C) well defined. Claw (Fig. 4D) with large basal tooth 0.68 times as long as claw. Wing. Length 2.2 mm. Costa with dark spinules and hairs except hairs on basal portion yellow. Subcosta with dark hairs except near apex bare. Hair tuft on stem vein dark brown. Basal section of vein R fully haired; R 1 with dark spinules and hairs; R 2 with hairs only. Basal cell absent. Haltere. White except basal stem darkened. Abdomen. Basal scale ochreous, with fringe of whitish-yellow hairs. Dorsal surface of abdomen medium brown to dark brownish except basal 1/2 of segment 2 yellow, moderately covered with yellow fine short hairs and dark short to long hairs; tergites of segments 2 and 6–9 shiny when illuminated at certain angles. Ventral surface of segments 2 and 3 entirely whitish-yellow, and those of other segments light to dark brown; sternal plate on segment 7 undeveloped. Genitalia. Sternite 8 (Fig. 4E) well sclerotized and bare medially, covered with 8–10 long hairs on each side. Ovipositor valves triangular, thin, membranous, moderately covered with microsetae; inner margins convex, somewhat sclerotized, and slightly separated from each other. Genital fork (Fig. 4F) of usual inverted-Y forms; stem slender and well sclerotized; arms of moderate width, lateral plate of each arm with thin lobe directed posteromedially. Paraproct in ventral view (Fig. 4G) concave anterolaterally, with 3 sensilla on anteromedial surface; paraproct in lateral view (Fig. 4H) somewhat produced ventrally, 0.62 times as long as wide, with 8–10 medium-long to long hairs on lateral and ventral surfaces. Cercus in lateral view (Fig. 4H) short, rounded posteriorly, 0.8 times as long as its greatest width. Spermatheca (Fig. 4I) ellipsoidal, 1.28 times as long as its greatest width, well sclerotized except duct and small area near juncture with duct unsclerotized, and with hexagonal pattern on surface; internal setae absent; both accessory ducts slender, subequal in diameter to major one.

Male. Body length 2.3 mm. Head, somewhat wider than thorax. Upper eye yellowish brown, consisting of 13 vertical columns and 14 horizontal rows of large facets. Face brownish black, grayish-white pruinose. Clypeus black, whitish pruinose, densely covered with golden-yellow scale-like medium-long hairs (directed upward and lateral) interspersed with several dark brown simple longer hairs. Antenna composed of scape, pedicel and 9 flagellomeres, yellow to brown; 1 st flagellomere elongate, 1.67 times as long as 2nd one. Maxillary palp light to medium brown, with 5 segments, proportional lengths of 3 rd, 4 th, and 5 th segments 1.00:0.6:1.1; 3 rd segment (Fig. 5A) widened apically; sensory vesicle (Fig. 5A) ellipsoidal, small (0.21 times as long as 3 rd segment), and with small opening. Thorax. Scutum slightly darker than female and short hairs on scutum golden yellow. Legs. Foreleg: coxa yellow; trochanter yellow with some portions light brown; femur light brown except apical cap brown; tibia brown with median 2/3 light brown and covered with dark brown hairs; tarsus brown to dark brown; basitarsus moderately dilated 6.0 times as long as its greatest width. Midleg: coxa yellowish brown; trochanter yellow to brown; femur yellow except apical 1/4 brown; tibia medium brown to dark brown; tarsus dark brown to brownish-black except anterior surface of little less than basal 1/2 of basitarsus dark yellow to light brown. Hindleg: coxa dark yellow to brown; trochanter yellow; femur light brown except apical 1/2 dark brown; tibia brown except subbasal and apical portion dark brown; tarsus medium to dark brown except basal 1/2 (or little less) of basitarsus whitish-yellow and little less than basal 1/3 of 2nd tarsomere white; basitarsus (Fig. 5B) slender, spindle-shaped, 4.4 times as long as wide, and 0.4 and 0.6 times as wide as greatest width of tibia and femur, respectively; calcipala (Fig. 5B) nearly as long as wide, and 0.3 times as wide as greatest width of basitarsus. Pedisulcus (Fig. 5B) well defined. Wing. Length 1.84 mm. Costa with dark brown spinules as well as dark brown hairs except basal portion with patch of yellowish hairs. Subcosta bare. Hair tuft on stem vein dark brown. Basal portion of radius fully haired; R1with dark spinules and hairs and R2with hairs only. Basal cell absent. Halter. Yellowish brown except outer surface ochreous, basal stem darkened and apex white. Abdomen. Basal scale dark brown, with fringe of light to medium brown hairs. Dorsal surface of abdomen dark brown except segment 2 light brown (though posterior 1/4 of dorsal surface brown), covered with dark brown short to long hairs; segments 2, 5–7 with shiny dorsolateral or lateral patches; ventral surface of segment 2 yellow, those of segments 3 and 4 yellow except sternites medium brown, and those of other segments medium to dark brown. Genitalia. Coxite in ventral view (Fig. 5C) quadrate, 1.1 times as long as its greatest width. Style in ventral view (Fig. 5C) greatly bent inward, slightly tapered from base to apex, pointed apically and with apical spine; style in medial view longer than coxite (0.8 times as long as coxite), gently bent inward, nearly parallel-sided, with apical spine; style in ventro-lateral view (Fig. 5D) greatly tapered toward middle, then parallel-sided, with rounded apex. Ventral plate in ventral view (Fig. 5E) with body broad, 0.6 times as long as wide, narrowed posteriorly, with anterior margin concave, and posterior margin rounded, densely covered with microsetae on ventral surface; basal arms of long, directed forward, then divergent apically; ventral plate in lateral view moderately produced ventrally; ventral plate in end view (Fig. 5F) body and ventrally-produced median process nearly equilateral triangular. Median sclerite (Fig. 5E) thin, plate-like, wide. Paramere (Fig. 5G) of moderate size, with 3 distinct long and stout hooks and several smaller ones. Aedeagal membrane moderately setose, slightly sclerotized at base but dorsal plate not well defined. Ventral surface of abdominal segment 10 without distinct hairs near posterior margin. Cercus in lateral view (Fig. 5H) small, rounded, with 5–7 hairs.

Pupa (n =6). Body length 3.0– 3.1 mm. Head. Integument dark yellow, moderately covered with small round tubercles; antennal sheath with protuberance; face with pair of simple very long trichomes with uncoiled apices, and frons with 3 pairs of simple very long trichomes with coiled or uncoiled apices; 3 frontal trichomes on each side arising close together, subequal in length to one another and slightly longer than facial one. Thorax. Integument yellow, covered with round tubercles, with 3 simple very long dorsomedial trichomes with coiled apices, 1 simple very long anterolateral trichome with coiled apices, 1 simple very long mediolateral trichome with uncoiled apex, and 3 simple ventrolateral trichome with ucoiled apices (1 medium-long and 2 short) on each side. Gill (Fig. 6A) composed of 8 slender thread-like filaments, arranged as [(1 + 2) + (1 + 2)] + 2 filaments from dorsal to ventral, with short common basal stalk having somewhat swollen transparent organ ventrally at base; common basal stalk 0.3 times length of interspiracular trunk; both primary and secondary stalks of dorsal triplet short, primary and secondary stalks of middle triplet medium-long; length of secondary stalk of middle triplet slightly longer than stalk of ventral pair; stalk of ventral pair medium-long, 2.4 times length of common basal stalk and 0.8 times length of interspiracular trunk; stalk of ventral pair 0.94–0.95 times as thick as primary stalk of middle triplet, and 0.86–0.89 times as thick as primary stalk of dorsal triplet; primary stalk of dorsal triplet lying against stalk of ventral pair at angle of 80–90 degrees or little more when viewed laterally; all filaments yellowish brown, gradually tapered toward apex; entire length of filaments (measured from base of gill to tips of filaments) based on one pupa as follows: 1.4–1.5 mm for dorsal triplet, 1.3–1.5 mm for middle triplet and 1.6–1.7 mm for ventral paired filaments; cuticle of all filaments with well-defined annular ridges and furrows though gradually becoming indistinct from middle to apex, densely covered with minute tubercles. Abdomen. Dorsally, segments 1 and 2 brownish yellow and with tubercles; segment 1 with 1 simple slender medium-long hair-like seta on each side; segment 2 with 1 simple medium-long and 3 short hair like setae on each side; segments 3 and 4 each with 4 hooked spines and 1 short hair like seta on each side; segment 5 lacking spine–combs and 1 short hair like seta on each side; segments 6–9 each with spine-combs in transverse row (though those on segment 9 slightly smaller than those on segment 8 and comb-like groups of minute spines on each side; segment 9 with pair of triangular flat terminal hooks, of which outer margin slightly longer than inner margin and not crenulated (Fig. 6B). Cocoon. Wall-pocket-shaped, thinly and moderately woven, anterior margin somewhat thickly woven, with dorsal portion slightly produced anteriorly when viewed dorsally; posterior 1/2 with floor roughly or moderately woven; individual threads visible; 3.5 mm long by 2.1 mm wide.

Mature larva (n =13). Body length 3.9–4.1 mm. Body creamy to color markings as follows: thoracic segment 1 encircled with ochreous broad transverse band (though disconnected ventrally), proleg grayish, thoracic segments 2 and 3 grayish dorsally and each with distinct ochreous wide areas ventrally, abdominal segments 1–4 each encircled with yellowish brown broad band, abdominal segments 5–8 almost entirely covered by yellowish brown transverse broad band on dorsal and dorsolateral surfaces; abdominal segments 5 and 6 each with W-shaped broad transverse grayish-brown band on dorsolateral surfaces of posterior 1/2 of each segment; abdominal segment 7 and 8 with transverse yellowish brown band on ventral surface; Cephalic apotome yellowish brown, and sparsely covered with simple minute setae; head spots indistinct. Lateral surface of head capsule yellowish brown except eye-spot region yellow, and very sparsely covered with simple minute setae; spots indistinct. Ventral surface of head capsule yellowish brown except somewhat darkened area near posterior margin on each side of postgenal cleft, and very sparsely covered with simple minute setae. Antenna composed of 3 segments and apical sensillum, 1.1 times longer than stem of labral fan; proportional lengths of 1st, 2nd, and 3rd segments 1.00:1.40:1.03. Labral fan with 28 main rays. Mandible (Fig. 6C) with 3 comb-teeth same length from 1 st to 3 rd; mandibular serrations composed of 2 teeth (1 medium-sized and 1 small); major tooth at acute angle against mandible on apical side; supernumerary serrations absent. Hypostoma (Fig. 6D) with row of 9 apical teeth; median and each corner tooth not prominent (though median tooth slightly longer than corner teeth) and longer than 3 intermediate teeth on each side; lateral margin smooth; 4 hypostomal bristles per side lying parallel to lateral margin. Postgenal cleft (Fig. 6E) arrow-headshaped, 3.04 times as long as postgenal bridge. Cervical sclerite composed of 2 very pale small pieces, not fused to occiput, moderately separated medially from each other. Thoracic cuticle finely covered with minute dark spinules. Abdominal cuticle almost bare except few posterior segments sparsely to moderately covered with simple minute setae dorsally and dorsolaterally and last segment densely covered with colorless simple setae on each side of anal sclerite. Rectal scales absent. Rectal papilla compound, each of 3 lobes with 5 finger-like secondary lobules. Anal sclerite of usual X-form, with anterior arms little shorter (0.86 times as long as posterior arms) than posterior ones, broadly sclerotized at base; accessory sclerite absent. Last abdominal segment expanded ventrolaterally forming double bulges on each side, visible as large conical ventral papilla when viewed from side. Posterior circlet with 64 rows of hooklets with up to 15–18 hooklets per row.

Etymology. The species is name krishnani is in honor of Professor M. Krishnan, Vice Chancellor of Madurai Kamaraj University, who contributed many works in the field of Entomology of India

Type series. Holotype, Female (preserved in ethanol), reared from a pupa, collected from a fast-flowing stream (width 3–5 m, depth 5–30 cm, diversified substrates stream, water temperature 23.0°C, exposed to the sun, altitude 527 m, 14º58′36″N, 74º46′40″E), Balur stream of Central Western Ghats, Kumta taluk, Uttara Kannada district, Karnataka state, India, 20-XI-2016, by S. Anbalagan & S. Vijayan; Paratype, 2 females, 2 males, 8 pupae, 24 mature larvae, same data as the holotype, holotype and paratypes deposited in CRAE (No: SGB004).

Habitat. The larvae and pupae of Simulium (Gomphostilbia) krishnani sp. nov. are abundantly found in snacks cover, polythene sheet and leaf litter submerged in water.