Simulium (Nevermannia) letense Takaoka & Shrestha, 2010

Takaoka, Hiroyuki & Shrestha, Suchitra, 2010, New species of black flies (Diptera: Simuliidae) from Nepal 2731, Zootaxa 2731, pp. 1-62 : 32-37

Simulium (Nevermannia) letense Takaoka & Shrestha sp. nov.

Description. Female. Body length 3.4 mm. Head. Slightly narrower than width of thorax. Frons dark brown, thinly whitish-gray pruinose, moderately covered with whitish-yellow recumbent short hairs (except mediolongitudinal area bare) interspersed with few dark brown long hairs along lateral margins; frontal ratio 1.40:1.00:1.42. Frons-head ratio 1.00:4.10. Fronto-ocular area ( Fig. 17A) directed laterally and slightly upward, rounded apically. Clypeus ( Fig. 17B) dark brown, thinly whitish-gray pruinose, slightly shiny at certain angle of light, sparsely covered with yellow short hairs interspersed with several dark brown long hairs though mediolongitudinal area of upper 3/5 widely bare. Labrum 0.93 times as long as clypeus. Antenna composed of scape, pedicel and 9 flagellomeres, entirely dark brown; 1st flagellomere 2.09 times as long as 2nd one. Maxillary palp composed of 5 segments, medium brown, proportional lengths of 3rd, 4th, and 5th segments 1.00:0.87:1.39; 3rd segment ( Fig. 17C) somewhat enlarged; sensory vesicle ( Fig.17 C) enlarged, ellipsoidal, 0.41 times as long as 3rd segment, and with large opening apically. Maxillary lacinia with 12 inner and 14–16 outer teeth. Mandible with 28 inner and 12 outer teeth. Cibarium ( Fig. 17D) with several very minute processes on transparent membrane covering anterior portion. Thorax. Scutum dark brown to brownish-black except anterolateral calli medium brown, slightly shiny at certain angle of light, densely covered with whitish-yellow to yellow recumbent short hairs interspersed with dark brown long upright hairs on prescutellar area. Scutellum dark brown, slightly shiny when illuminated at certain angle of light, covered with whitish-yellow short hairs and dark brown long hairs. Postnotum dark brown, slightly shiny when illuminated at certain angle of light, bare. Pleural membrane bare. Katepisternum dark brown, longer than deep, slightly shiny when illuminated at certain angle of light, and bare. Legs. Medium to dark brown. Fore basitarsus somewhat dilated, 7.48 times as long as its greatest width. Hind basitarsus ( Fig. 17E) slender, nearly parallel-sided, 7.35 times as long as wide, and 0.72 and 0.68 times as wide as tibia and femur, respectively; calcipala ( Fig. 17E) well developed, short, 0.79 times as long as basal width, and 0.49 times as wide as greatest width of basitarsus; pedisulcus ( Fig. 17E) well developed; claw ( Fig. 17F) with small subbasal tooth. Wing. Length 3.0 mm. Costa with dark brown spinules and hairs except basal patch of hairs yellowish-white. Subcosta with dark brown hairs except apical 1/3 bare. Hair tuft on stem vein dark brown. Basal portion of radial vein fully haired. R 1 with dark brown spinules and hairs. R 2 with dark brown hairs only. Basal cell and basal median cell absent. Abdomen. Basal scale medium to dark brown, with fringe of yellowish-white long hairs; dorsal surface of abdominal segments medium brown except base of segment 2 yellowish-white, rest of segment 2 and posterior 1/3 of segment 3 light brown, and all tergites medium brown, and moderately covered with whitish-yellow short hairs as well as dark brown short to medium-long hairs; tergites 7–9 shiny when illuminated at certain angle of light; ventral surface of segments 2–5 light ochreous, segments 6 and 7 light brown and segment 8 medium brown; segment 7 with weakly defined large sternal plate medially. Genitalia. Sternite 8 ( Fig. 17G) bare medially, and with 15–17 short to long hairs on each side. Ovipositor valves ( Fig. 17G) roughly triangular, rounded medioposteriorly, thin, membranous, densely covered with microsetae interspersed with 5–9 fine short setae (though 1 seta on right side medium-long); inner margin moderately sclerotized and narrowly darkened. Genital fork ( Fig. 17H) of usual inverted-Y form, stem slender and well sclerotized; arms widened, each with angulated strongly-sclerotized apical ridge directed anterodorsally or laterodorsally. Paraproct in ventral view ( Fig. 17I) subquadrate, with stronglysclerotized anterior surface, covered with 11–13 medium-long and long hairs on ventral and lateral surface, with 7 or 8 sensilla on anteromedial transparent surface; paraproct in lateral view ( Fig. 17J) slightly produced ventrally beyond ventral margin of cercus. Cercus in ventral view ( Fig. 17I) narrow, with widely concave inner surface; cercus in lateral view ( Fig. 17J) rounded, 0.68 times as long as wide, and with several dark medium-long to long hairs. Spermatheca ( Fig. 17K) small, ovoidal, 1.22 times as long as its greatest width, well sclerotized except area at juncture with duct, with reticulate surface pattern; internal setae absent; main duct and both accessory ducts subequal in diameter to one another.

Male. Unknown.

Pupa. Body length (excluding gill filaments) 3.0– 3.2 mm. Head. Integument ( Fig. 18A) dark yellow, moderately covered with relatively large tubercles bearing minute secondary projections ( Fig. 18B) on frons, sparsely covered with small tubercles on each lateral surface of face and almost bare on down surface of face; antennal sheath in lateral view ( Fig. 18C) with undulate outer margin, sparsely or moderately covered with small tubercles, some of which bear minute secondary projections; frons with 2 simple slender trichomes of variable lengths with uncoiled apices on each side (e.g., 2 long on left side ( Fig. 18A), 1 long and 1 short on right side in 1 pupa; 2 short on left side, 2 medium-long on right side in another pupa); face with 1 simple long trichome with uncoiled apex ( Fig. 18A) on each side. Thorax. Integument ( Fig. 18D,E) light yellowishbrown, with 5 distinct elongate carinae on dorsal surface of anterior 1/2 (i.e., 1 medial carina running from anterior margin backward to middle and turning outward for very short distance, 2 submedial carinae running inward along anterior margin from base of gill, and turning backward to middle, 2 lateral carinae running backward from base of gill along dorsolateral margin to middle and turning inward for short distance, posterior tips of these cariane approaching close together but not contiguous to one another at same height, and pair of round submedial ridges on dorsal surface of posterior 1/3, which are located close together but not contiguous to each other at same height; thoracic integument covered with relatively large tubercles bearing minute secondary projections (similar to those on frons) densely on carinae and ridges, moderately on intercarinae areas ( Fig. 18F), and covered with relatively smaller tubercles on dorsal surface of posterior 1/4 (or 1/3) and on each lateral surface; thorax on each side with 4 simple short slender trichomes with uncoiled apices (1 on submedian carina, 3 on area between submedian and lateral carinae) dorsally ( Fig. 18D), 1 simple medium-long trichome with uncoiled apex mediolaterally ( Fig. 18D,E), and 3 simple trichomes with uncoiled apices (1 long, 1 medium-long, 1 short) ventrolaterally ( Fig. 18E), and 2 simple trichomes with uncoiled apices (1 medium-long, 1 short) anterolaterally below base of gill ( Fig. 18E). Gill ( Fig. 18G) with 4 slender thread-like short filaments, much shorter than pupal body, arising at same level from short common basal stalk, which is directed outward and black; common basal stalk little thicker than interspiracular trunk, and with transparent swollen portion ventrally at base; all filaments subequal in length (1.4–1.6 mm long) and thickness to one another, medium brown, very slightly tapered toward apex, furnished with annular ridges and furrows at very short regular intervals, and densely covered with minute tubercles on outer surface. Abdomen. Dorsally, segment 1, anterior 1/2 of segments 2–4 very weakly sclerotized and light brown; segments 1 and 2 sparsely tuberculate; segment 1 with 1 simple slender short seta on each side; segment 2 with 1 simple slender short seta and 5 dark spinous very short setae on each side; segments 3 and 4 each with 4 dark stout hooks (though 3 hooks on each side on segment 3 in 1 pupa) and 1 dark very short spinous seta on each side; segments 5–9 without spine-combs in 1 pupa, or segments 7 and 8 each with spine-combs lying transversely along anterior margin on each side (though 1 and 2 spines on segment 7, and 4 and 6 spines on segment 8) in 1 pupa; segments 5–9 each with comb-like groups of minute spines in transverse rows on each side; segment 9 with pair of cone-shaped terminal hooks ( Fig. 18H). Ventrally, segment 4 with 1 dark simple hooklet (slightly shorter and smaller than those on segments 5–7) and 3 simple short setae (1 dark, 2 yellow) on each side; segment 5 with 2 dark bifid hooks and few simple short setae on each side; segments 6 and 7 each with 1 dark bifid inner hook and 1 dark simple or bifid outer hook, and few simple short setae on each side; segments 4–8 each with comb-like groups of minute spines. Cocoon ( Fig. 18I). Flat, round, with thickly woven round anterior opening in dorsal view; cocoon moderately woven, individual threads visible or not; floor woven on posterior 1/2; 4.0– 4.6 mm long by 3.2–3.4 mm wide. Cocoon covering only abdomen and posterior tip of thorax of pupa.

Mature larva. Body length 6.0– 6.2 mm. Body color creamy though posterior abdominal segments very faintly grayish dorsally in 1 larva, or body color almost entirely grayish in 1 larva. Cephalic apotome yellow to light brown; head spots positive though posteromedial and posterolateral spots blurred. Lateral surface of head capsule yellow to light brown except eye-spot region whitish and area in front of posterior margin somewhat darkened; eyebrow darkened and well-defined, with 1 dark spot; 2 large and 1 or 2 small dark spots near posterior margin, and 1 small dark spot below eye-spot region present. Ventral surface of head capsule ( Fig. 19A) light brown though near posterior margin of hypostoma yellow, with dark brown area on each side of postgenal cleft; elongate spot on each side of postgenal cleft positive. Cervical sclerites composed of 2 brown rod-like small pieces, not fused to occiput, widely separated from each other. Antenna composed of 3 segments and apical sensillum, much longer than stem of labral fan; proportional lengths of 1st, 2nd, and 3rd segments 1.00:1.23–1.49:0.53–0.63. Labral fan with 38 rays. Mandible ( Fig. 19B,C) with 1st comb-tooth longest, followed by 2nd one which is as long as or slightly longer or shorter than 3rd one; mandibular serrations composed of 2 teeth (1 large and 1 small); large tooth at obtuse angle to mandible on apical side; 1– 3 supernumerary serrations present. Hypostoma ( Fig. 19D) with row of 9 apical teeth, median tooth most prominent, followed by corner teeth, and intermediate teeth smallest; lateral margins smooth except near apex serrated; hypostomal bristles 6 or 7 in row, lying parallel to or slightly divergent from lateral margin on each side. Postgenal cleft ( Fig. 19A,E) of medium-size, 1.1 times as long as postgenal bridge, somewhat pointed or rounded anteriorly. Histoblast of pharate pupal gill ( Fig. 19F) with 4 slender filaments; basal common stalk blackish inside. Thoracic and abdominal cuticle almost bare except last abdominal segment moderately covered with colorless minute setae on both sides of anal sclerite. Rectal scales darkened, easily discernible. Rectal organ compound, each lobe with 18–24 finger-like secondary lobules. Anal sclerite X-shaped, with basal juncture area broadly sclerotized; anterior arms short, broad, 0.65 times as long as posterior ones; accessory sclerites absent; sensillum absent. Ventral papillae small and conical. Posterior circlet with 85 rows of up to 12 hooks per row.

Type specimens. Holotype female (with its associated pupal exuviae and cocoon) (preserved in 80% ethanol), collected from a very rapidly-flowing stream (width 2m, water temperature 10.0˚C, exposed to the sun, altitude 2,532 m, 28˚64’32.9” N, 83˚66’32.0” E), Lete , Mustang, Nepal, 23.IX.2009 . Paratypes: 2 mature larvae, same date and data as those of the holotype; 3 pupae collected from a small water canal (water temperature 21.0˚C, exposed to the sun, altitude 1,606 m, 28˚24’06.8” N, 83˚50’32.4” E) moderately flowing through hilly area, Jhakrithan , Lekhani, Baglung, Nepal, 23.IX.2009 .

Biological notes. The pupae and larvae of this new species were collected from grass leaves trailing in water. Associated species are S. (N.) lekhaniense sp. nov., S. (M.) dattai and S. (S.) sp.

Etymology. The species name letense refers to the locality name, Lete, where this new species was collected.

Remarks. Simulium (N.) letense sp. nov. is assigned to the vernum species-group within the subgenus Nevermannia redefined by Takaoka (2003) in that it has the genital fork with no distinct projection ( Fig. 17H), and the paraproct which is longer than the cercus ( Fig. 17J) in the female, the gill with four filaments ( Fig. 18G) in the pupa and the mandible with supernumerary serrations ( Fig. 19B,C) in the larva.

This new species appears to be closely related to S. (N.) planipuparium Rubtsov originally described from Tadzhikistan ( Rubtsov 1989) in sharing the pupal thorax with distinct carinae on the dorsal surface ( Fig. 18D,E) coupled with the pupal gill with four short slender filaments ( Fig. 18G) and the round flat cocoon with an anteroventral collar ( Fig. 18I). However, this new species is distinguished from the latter known species in the female by the claw with a small subbasal tooth ( Fig. 17F) (in place of a large tooth) and in the pupa by the presence of a medial carina and a pair of round ridges in addition to the submedian and lateral carinae ( Fig. 18D,E), and the pupal gill with the black common basal stalk ( Fig. 18G) (not all portions of the gill filaments black).