Simulium (Simulium) nigripilosum Edwards, 1933

Takaoka, Hiroyuki, Sofian-Azirun, Mohd, Ya’Cob, Zubaidah, Chen, Chee Dhang, Lau, Koon Weng, Fernandez, Kevin & Lardizabal, Maria Lourdes, 2015, Revision of the Simulium (Simulium) melanopus species-group (Diptera: Simuliidae) in Sabah, Malaysia, Zootaxa 3985 (1), pp. 1-30 : 14-20

Simulium (Simulium) nigripilosum Edwards, 1933

Simulium nigripilosum Edwards, 1933: 256 (Female) .

This species was originally described on the basis of females and males collected at Kamborangah in the Kinabalu National Park ( Edwards 1933). Smart and Clifford (1969) associated their adult females reared from pupae with this species, but this association was shown to be wrong ( Takaoka 1996). The species thought of as S. (S.) nigripilosum by Smart and Clifford (1969) was described as a new species, S. (S.) beludense ( Takaoka 1996) , and was placed in the S. argentipes species-group ( Takaoka and Saito 2007). The genitalia of the holotype female were illustrated by Takaoka (1983).

In the present study, the holotype pinned female was examined. The female is redescribed based on females reared from pupae, and the male and pupa are described for the first time.

Female. Body length 2.6–2.7 mm. Head. Narrower than width of thorax. Frons black, shiny, with several dark stout hairs along each lateral margin and few hairs near lower margin; frontal ratio 1.32–1.35:1.00:1.11–1.14; frons-head ratio 1.00:3.77–4.07. Fronto-ocular area shallow, rounded or triangular dorsolaterally. Clypeus black, whitish-gray pruinose, shiny when illuminated at certain angles, moderately covered with dark stout hairs (though mediolongitudinal area narrowly bare in one female). Labrum 0.61–0.68 times as long as clypeus. Antenna composed of scape, pedicel and nine flagellomeres, brownish black except scape and pedicel medium brown, and base of first flagellomere dark yellow. Maxillary palp light brown except third segment dark brown, composed of five segments, proportional lengths of third, fourth, and fifth segments 1.00:1.02–1.08:1.67–2.00; third segment ( Fig. 7 A) slightly enlarged; sensory vesicle ( Fig. 7 A) ellipsoidal, 0.30–0.35 times as long as third segment, with large round opening. Maxillary lacinia with 10 inner and 14 or 15 outer teeth. Mandible with 24–27 inner and 13 or 14 outer teeth. Cibarium (7B) with cornuae well developed, and with 68–70 minute processes dorsomedially. Thorax. Scutum black, thinly whitish-gray pruinose and shiny when illuminated at certain angles, moderately covered with light-brown short hairs interspersed with dark-brown long upright hairs on prescutellar area. Scutellum black, with dark-brown upright long and short hairs. Postnotum black, whitish-gray pruinose and shiny when illuminated at certain angles, and bare. Pleural membrane bare. Katepisternum longer than depth, black, thinly whitish-gray pruinose and shiny when illuminated at certain angles and bare. Legs. Nearly as in female of S. (S.) crassimanum except following characters: Foreleg: basitarsus greatly dilated, 4.6 times as long as its greatest width. Midleg: tibia ( Fig. 7 C) brownish black with base yellow though extreme tip darkened; tarsus ( Fig. 7 D) brownish black except basal two-thirds of basitarsus, basal tips of second and third tarsomeres whitish yellow. Hind leg: femur brownish black except apical cap black; tibia ( Fig. 7 E) brownish black with apical cap black, and base yellowish white; tarsus ( Fig. 7 F) brownish black except basal three-fifths of basitarsus (though base dark brown) and basal half of second tarsomere yellowish white; basitarsus nearly parallel-sided, 5.90 times as long as its greatest width, 0.71 and 0.63 times as wide as greatest widths of hind tibia and femur, respectively; calcipala nearly as long as width at base, 0.45 times as wide as basitarsus; pedisulcus well developed; claw ( Fig. 7 G) with small basal tooth 0.29 times length of claw. Wing. Length 2.5–2.6 mm. Other features as in female of S. (S.) crassimanum . Halter and Abdomen. Nearly as in female of S. (S.) crassimanum except each ventrolateral surface of segments 3–8 with grayish spot, ventral surface of segment 2 grayish and those of other segments medium to dark brown except that of segment 8 blackish. Terminalia . Sternite 8 ( Fig. 7 H) well sclerotized, moderately depressed medially, moderately covered with 17–26 long stout and medium-long fine hairs on each side; ovipositor valve ( Fig. 7 H, I) tapered apically with round apex, bent ventrally, and covered with 36 short to long hairs; inner margins well sclerotized, moderately concave medially, moderately separated from each other. Genital fork ( Fig. 7 J) of inverted-Y form; stem slender and well sclerotized; arms slender, each with strongly-sclerotized lateral ridge directed dorsally. Paraproct in lateral view ( Fig. 7 K) much produced anteroventrally, covered with eight mediumlong to long stout hairs and numerous short fine hairs on lateral surface; paraproct anteroventrally with thin elongate moderately-sclerotized plate having round apical tip and 12 or 13 short setae scattered on its surface. Cercus in lateral view ( Fig. 7 K) short, with posterior margin nearly straight, 5.7 times as wide as its greatest length, and covered with numerous hairs. Spermatheca ( Fig. 7 L) nearly globular, 1.13 times as long as greatest width, well sclerotized except duct and wide area of junction with duct unsclerotized, without reticulate surface patterns; minute internal setae present; both accessory ducts subequal in diameter to each other, and also to that of main duct.

Male. Body length 2.6–2.9 mm. Head. Nearly as wide as or slightly wider than thorax. Upper eye consisting of large facets in 17–19 vertical columns and in 19–21 horizontal rows on each side. Clypeus brownish-black, whitish-pruinose, shiny and iridescent when illuminated at certain angles, sparsely covered with dark-brown long hairs. Antenna composed of scape, pedicel and nine flagellomeres, brownish-black; first flagellomere elongate, 2.0 times length of second one. Maxillary palp light brown except third segment dark brown, composed of five segments, proportional lengths of third, fourth, and fifth segments 1.00:1.14–1.22:2.23–2.24; third segment ( Fig. 8 A) of normal size; sensory vesicle ( Fig. 8 A) small, globular or ellipsoidal, 0.25 times length of third segment, and with small opening. Thorax. Nearly as in male of S. (S.) crassimanum except scutellum and postnotum black, and scutum with white spots on shoulders somewhat smaller ( Fig. 8 B). Legs. Color pattern almost similar to that of female including all tibiae with iridescent sheen widely on outer or posterior surface except hind basitarsus ( Fig. 8 C) brownish black except little less than basal half yellowish white (though base dark brown). Fore basitarsus moderately dilated, 6.35–6.47 times as long as its greatest width. Hind basitarsus ( Fig. 8 C) greatly enlarged, gradually widened toward apical one-fourth, then roundly narrowed, 3.45–3.49 times as long as its greatest width, 1.03–1.05 and 1.05–1.15 times as wide as greatest widths of hind tibia and femur, respectively; calcipala ( Fig. 8 C) slightly longer than its basal width, and 0.23 times as wide as greatest width of basitarsus; pedisulcus well developed. Wing. Length 2.3–2.6 mm. Other features as in female except subcosta entirely bare or with few hairs. Halter and Abdomen. Nearly as in male of S. (S.) crassimanum except dorsal surface of all segments black, and ventral surface dark brown to brownish black except segment 2 grayish. Genitalia. Coxites, styles and ventral plate in ventral view as in Fig. 8 D. Coxite in ventrolateral view ( Fig. 8 E) nearly quadrate, 0.86 times as long as wide. Style in ventrolateral view ( Fig. 8 F) elongate, 1.67 times length of coxite, 2.58 times as long as its greatest width, sinuous, widened from base to basal one-fourth, narrowed to middle, slightly widened to apical one-fourth, then slightly narrowed toward round apex, and with stout apical spine; style in medial view ( Fig. 8 G) flattened dorsoventrally, gradually narrowed toward apex, and without basal or subbasal protuberance. Ventral plate in ventral view ( Fig. 8 D) with body nearly rectangular having ventrally produced median process that is bare except parts of lateral and anterior surfaces covered with minute setae, and is furnished with several teeth in vertical row on each posterolateral margin; basal arms of moderate length, stout and divergent; ventral plate in lateral view ( Fig. 8 H) with body and its ventrally produced process with rounded ventral apex, with dentate posterior margin, and covered with minute setae anterolaterally; ventral plate in caudal view ( Fig. 8 I) with body and ventrally produced median process gradually tapered from base to apex, bare, with several teeth in vertical row on each lateral margin. Median sclerite in lateral view ( Fig. 8 H) moderately sclerotized, folded backward and then curved dorsally, and in caudal view ( Fig. 8 J) plate-like, slightly widened toward apical one-third, then slightly narrowed. Paramere ( Fig. 8 K) wide basally and with several parameral hooks apically. Aedeagal membrane ( Fig. 8 L) moderately covered with minute setae, without sclerotized dorsal plate. Ventral surface of tenth abdominal segment ( Fig. 8 M, N) without distinct hairs. Cercus ( Fig. 8 M, N) rounded laterally, with 14 or 15 distinct hairs.

Pupa. Body length (excluding gill filaments) 3.0 mm. Head. Integument whitish yellow, except frons and antennal sheaths yellowish brown, densely covered with round tubercles except posterior two-thirds of antennal sheaths bare: frons with two unbranched short trichomes ( Fig. 9 A) on each side; face with one unbranched short stout trichome ( Fig. 9 B) on each side; frontal trichomes slightly shorter than facial ones. Thorax. Integument yellowish brown on anterior half, yellowish on posterior half, densely or moderately covered with round tubercles or cone-shaped smaller tubercles except lateral surface of posterior half bare; thorax with two stout anterodorsal trichomes (one medium-long, one short) ( Fig. 9 C), two anterolateral trichomes (one short and slender, one long and somewhat stout) ( Fig. 9 D), one short stout mediolateral trichome ( Fig. 9 E), and three ventrolateral trichomes (two long and stout, one short and slender) ( Fig. 9 F), on each side; all unbranched. Gill ( Fig. 9 G) with six slender thread-like filaments in pairs; dorsal pair short stalked, middle and ventral pairs short stalked or almost sessile; upper filament of dorsal pair longest (1.2–1.3 mm), two filaments of ventral pair shortest (0.6–0.7 mm), and three other filaments subequal in length (0.8–0.9 mm); relative thickness of filaments from dorsal to ventral when compared basally 1.00:0.64–0.67:0.46–0.67:0.51–0.57:0.41–0.46:0.40–0.41; upper filament of dorsal pair medium brown, lower filament of dorsal pair and four filaments of middle and ventral pairs light brown; all filaments gradually tapered toward apex; stalks of dorsal and ventral pairs at angle of 60–80 degrees when viewed laterally; cuticular surface with annular ridges and furrows in regular intervals (though irregular intervals in some portions), covered with minute tubercles. Abdomen. Dorsally, segment 1 yellowish to light brown, other segments unpigmented; segment 1 without minute tubercles and with one unbranched short slender seta on each side; segment 2 with one unbranched short slender seta and five unbranched minute setae on each side; segments 3 and 4 each with four unbranched hooked spines and one unbranched minute seta on each side; segments 5, 6 and 9 without spine-combs; segments 7 and 8 each with spine-combs in transverse row on each side; segments 6–9 each with comb-like groups of minute spines in transverse row on each side; segment 9 without terminal hooks. Ventrally, all segments unpigmented; segment 4 with one unbranched minute seta on each side; segment 5 with pair of bifid hooks submedially and one unbranched minute seta on each side; segments 6 and 7 each with pair of bifid inner and unbranched or bifid outer hooks widely spaced and one unbranched minute seta on each side. Grapnellike hooklets absent. Cocoon ( Fig. 9 H–K). Wall-pocket-shaped (anterolateral margins separated from each other as in Fig. 9 H though approaching anteroventrally and touching each other in a few cocoons as in Fig. 9 J), thickly woven, ochreous, not extended ventrolaterally; individual threads invisible; 3.1–3.4 mm long by 1.5–1.7 mm wide.

Specimens examined. Six females, five males, three pharate females, four pharate males, collected from a stream (width 0.5 m, depth 2–5 cm, shaded) slow flowing in a forest, on the right side of the trekking route to the peak of Mt. Kinabalu, 2 km up from Carson Waterfall, Mt. Kinabalu, Sabah, Malaysia, 10-IX-2007, by H. Takaoka; one female caught by a hand net, at the same place as above; one male, collected from a small stream (width 1.0 m, depth 7–10 cm, streambed rocky, water temperature 16.1˚C, shaded, altitude 1,890 m, 06˚01.870’ N/ 116˚32.834’ E), slow flowing in a natural forest, downstream of Carson Waterfall, Timpohon, Mt. Kinabalu, Sabah, 8-I-2015, by K. Fernandez; one pharate female, two pharate males, collected from a stream (width 1 m, depth 7–10 cm, streambed rocky, water temperature 16.1 ˚C, partially shaded, altitude 1,890m, 06˚01.870’ N/116˚32.834’ E) moderate to fast flowing in a natural forest, downstream of Carson Waterfall, Timpohon, Mt. Kinabalu, Sabah, 24- X-2014, by C.D. Chen, K.W. Lau, M.L. Lardizabal & K. Fernandez; one female, reared from a pupa, collected from a small stream (width 6.0 m, depth 0.5 m, streambed stony, water temperature 17.0˚C, partially shaded, altitude 1,714 m, 06˚01.337’ N/116˚36.420’ E), slow flowing in a natural forest, Mt. Kinabalu, Sabah, 16-VI-2014, by M. Sofian-Azirun, Z. Ya’cob, N.A. Jamil, C.D. Chen, K.W. Lau & M. Rasul; one male, reared from a pupa, collected from a stream (width 0.5 m, depth 2 cm, streambed concrete, water temperature 16.0 ˚C, partially shaded, altitude 1,934m, 06˚02.269’ N/116˚35.281’ E) moderately flowing in a cultivated field, Mesilau, Kundasang, Sabah, 24-X-2014, by C.D. Chen, K.W. Lau, M.L. Lardizabal & K. Fernandez.

Ecological notes. The biting habits are unknown, although one female was caught by a hand net while flying around a human. The pupae of this species were collected from trailing grasses and dead leaves of trees in the water. Associated species were S. (N.) borneoense , S. (S.) aeneifacies , S. (S.) crassimanum and S. (S.) sp.

Distribution. Sabah.

Remarks. The following characteristics of the holotype pinned female of S. (S.) nigripilosum are confirmed: antenna dark brown, fore coxa dark brown, fore tibia dark brown with a wide white area on the outer surface, mid tibia entirely dark brown to black, mid basitarsus yellowish on the basal two-thirds, hind tibia dark brown to black with the base yellow, hind basitarsus whitish on the basal two-thirds, claw with a small basal tooth, basal portion of the radial vein entirely bare. Females reared from pupae collected from Timpohon agree with the holotype female in the leg color except the mid tibia having a yellow base ( Fig. 7 C). This character of the mid tibia recognized in alcohol specimens, might have been overlooked in the pinned type specimen. The claw was erroneously described to be simple in the original description ( Edwards 1933).

The pupa of this species is characterized by the frons and dorsal surface of the thorax densely covered with round tubercles, gill with six filaments, of which the upper filament of the dorsal pair is much thicker than the other filaments ( Fig. 9 G), and wall-pocket-shaped cocoon ( Fig. 9 H, J)

Figures

FIGURE 7. Female of Simulium (Simulium) nigripilosum. (A) Third segment of maxillary palp with sensory vesicle (right side; front view). (B) Cibarium (front view). (C) Mid tibia (left side; outer view). (D) Tarsus of midleg (left side; outer view). (E) Hind tibia (left side; outer view). (F) Basitarsus and second tarsomere of hind leg (left side; outer view). (G) Claw. (H) Posterior tip of abdomen showing sternite 8 and ovipositor valves (ventral view). (I) Ovipositor valve (left side; anteroventral view). (J) Genital fork (ventral view). (K) Paraproct and cercus (right side; lateral view). (L) Spermatheca. Scale bars. 0.1 mm for C – F; 0.02 mm for A, B and G – L.

FIGURE 8. Male of Simulium (Simulium) nigripilosum. (A) Third segment of maxillary palp with sensory vesicle (right side; front view). (B) Scutum showing pruinose pattern (dorsal view). (C) Basitarsus and second tarsomere of hind leg (left side; outer view). (D) Coxites, styles and ventral plate (ventral view). (E) Coxite (right side; ventrolateral view). (F) and (G) Styles (right side; F, ventrolateral view; G, medial view). (H) Ventral plate and median sclerite (lateral view). (I) Ventral plate (caudal view). (J) Median sclerite (caudal view). (K) Paramere (left side; caudal view). (L) Aedeagal membrane (left half; caudal view). (M) and (N) Tenth abdominal segments and cerci (right side; M, lateral view; N, caudal view). Scale bars. 0.1 mm for C; 0.02 mm for A and D – N.

FIGURE 9. Pupa of Simulium (Simulium) nigripilosum. (A) Frontal trichomes. (B) Facial trichome. (C) – (F) Thoracic trichomes (C, anterodorsal; D, anterolateral; E, mediolateral; F, ventrolateral). (G) Anterior half of thorax and gill filaments (right side; outer view). (H) – (K) Cocoons showing two different types (H & J, dorsal view; I & K, lateral view). Scale bars. 1.0 mm for H – K; 0.1 mm for G; 0.02 mm for A – F.