Simulium (Simulium) laterale 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 : 8-14

Simulium (Simulium) laterale Edwards, 1933

Simulium laterale Edwards, 1933: 256 (Female) .

Simulium kinabaluense Smart and Clifford, 1969: 29 –30 (Female, male, pupa and larva). New synonym.

This species was originally described on the basis of females collected at Lumu Lumu in the Kinabalu National Park ( Edwards 1933). Smart and Clifford (1969) redescribed the female of this species from reared specimens and described the male, pupa and larva of this species. The paralectotype female of this species was examined and its genitalia were illustrated by Takaoka (1983).

In the present study, the lectotype and paralectotype pinned females (type designation made in 1988 by R.W. Crosskey) were examined. The female, male and pupa of S. (S.) laterale (formerly S. (S.) kinabaluense ) are redescribed based on newly collected specimens.

Female. Body length 3.0– 3.2 mm. Head. Narrower than width of thorax. Frons black, strongly shiny when illuminated at certain angles, with several dark stout hairs along each lateral margin and several shorter hairs near lower margin on each side; frontal ratio 1.16:1.00:1.00; frons-head ratio 1.00:4.38. Fronto-ocular area shallow, rounded or triangular laterally. Clypeus black, whitish-gray pruinose, shiny when illuminated at certain angles, moderately covered with dark stout hairs except small area near upper margin bare. Labrum 0.69 times as long as clypeus. Antenna composed of scape, pedicel and nine flagellomeres, brownish black except scape, pedicel and first flagellomere dark yellow when viewed ventrally, or scape, basal half of pedicel and base of first flagellomere dark yellow and apical half of pedicel medium brown when viewed dorsally. Maxillary palp light brown except third segment dark brown, composed of five segments, proportional lengths of third, fourth, and fifth segments 1.00:1.24:2.60; third segment ( Fig. 4 A, B) somewhat enlarged apically; sensory vesicle ( Fig. 4 A, B) ellipsoidal, 0.25–0.38 times as long as third segment, with medium-sized or large round opening. Maxillary lacinia with 13 or 14 inner and 17 outer teeth. Mandible with 29 inner and 14 outer teeth. Cibarium ( Fig. 4 C) with 85 minute processes medially; cornuae moderately developed. Thorax. Nearly as in female of S. (S.) crassimanum except scutum brilliantly shiny, in particular, bluish iridescent on shoulder and lateral portion along each lateral margin when illuminated at certain angles. Legs. Color nearly as in female of S. (S.) crassimanum except mid basitarsus brownish black except basal half or little less dark yellow, hind tibia black with base medium to dark brown, hind basitarsus ( Fig. 4 D) brownish black except basal half whitish yellow (though base dark brown), and second hind tarsomere ( Fig. 4 D) brownish black except basal one-third yellowish white. Fore basitarsus greatly dilated, 4.92 times as long as its greatest width. Hind basitarsus nearly parallel-sided, 6.60 times as long as its greatest width, 0.63 and 0.53 times as wide as greatest widths of hind tibia and femur, respectively; calcipala ( Fig. 4 D) nearly as long as width at base, 0.5 times as wide as basitarsus; pedisulcus well developed; claw ( Fig. 4 E) with small subbasal tooth 0.3 times length of claw. Wing. Length 2.6 mm. Other features as in female of S. (S.) crassimanum except subcosta with hairs but near apex bare. Halter and Abdomen. Nearly as in female of S. (S.) crassimanum except dorsal surface of abdomen dark brown to brownish black except dorsomedial portion of segment 2 light to medium brown, segments 3–5 each with light-brown narrow dorsolateral portions along anterior and posterior margins on each side, and segment 6 with light-brown narrow dorsolateral portion along anterior margin, which connected to light-brown portion along lateral margin of tergite on each side, and ventral surface of segments 2 and 3 light brown, those of others medium brown. Terminalia . Sternite 8 ( Fig. 4 F) moderately sclerotized, slightly depressed medially, moderately covered with 23–28 long stout and medium-long fine hairs on each side. Ovipositor valves ( Fig. 4 F, G) bent ventrally, making right angle to sternite 8, tapered apically with transparent bare round apex, membranous except narrow area along each inner margin well sclerotized, covered with about 30 short to long hairs on each side; inner margins well sclerotized, moderately concave medially, moderately separated from each other. Genital fork ( Fig. 4 H) of inverted-Y form; stem slender and well sclerotized; arms slender, each with strongly-sclerotized ridge directed dorsally. Paraproct in lateral view ( Fig. 4 I) much produced ventrally or anteroventrally, covered with several medium-long to long stout hairs and numerous short fine hairs on lateral surface; paraproct anteromedially with thin elongate moderately-sclerotized plate having round apical tip and 18 short setae scattered on its surface. Cercus in lateral view ( Fig. 4 I) short, with posterior margin nearly straight, 4.73 times as wide as its greatest length, and covered with numerous hairs. Spermatheca ( Fig. 4 J) nearly globular, 1.07 times as long as wide, well sclerotized except duct and 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 3.5 mm. Head. Slightly wider than thorax. Upper eye consisting of large facets in 17–19 vertical columns and in 18–20 horizontal rows on each side. Clypeus brownish-black, whitish-pruinose, shiny and silvery iridescent when illuminated at certain angles, moderately covered with dark-brown long hairs, though mediolongitudinal portion narrowly bare. Antenna composed of scape, pedicel and nine flagellomeres, dark-brown to brownish-black; first flagellomere elongate, 1.91 times length of second one. Maxillary palp light to medium brown except third segment dark brown, composed of five segments, proportional lengths of third, fourth, and fifth segments 1.00:1.17:2.54; third segment ( Fig. 5 A) somewhat widened apically; sensory vesicle ( Fig. 5 A) small, ellipsoidal, 0.19–0.23 times length of third segment, and with small opening. Thorax. Scutum ( Fig. 5 B) black, with brightly bluish iridescent pattern when illuminated at certain angles, composed of anterior pair of spots on shoulders, and large transverse band covering prescutellar area, which is connected to anterior pair of spots by broad band along lateral margins; anterior pair of spots rectangular, directed posteromedially, with pointed apices, moderately separated in middle from each other, and moderately separated from posterior transverse band; anterior pair of spots on shoulders rather stable, not disappearing depending on angles of light. Other features similar to those of female. Legs. Brownish black to black except narrow medial portion along outer margin of fore tibia whitish, and basal half of mid basitarsus and basal one-third of hind basitarsus medium brown. Fore and mid tibiae with iridescent sheen widely on outer and posterior surfaces, respectively, and hind tibia with sheen basally on posterior surface. Fore basitarsus greatly dilated, 5.08 times as long as its greatest width. Hind basitarsus ( Fig. 5 C) greatly enlarged, gradually widened toward middle, then somewhat narrowed toward apex, 4.01 times as long as its greatest width, 0.79 and 0.87 times as wide as greatest widths of hind tibia and femur, respectively; calcipala nearly as long as its basal width, and 0.30 times as wide as greatest width of basitarsus; pedisulcus well developed. Wing. Length 2.6 mm; other features as in female except subcosta entirely bare. Halter and Abdomen. Nearly as in male of S. (S.) crassimanum except dorsal surface of abdomen dark brown with medial portion of segment 2 light brown, narrow transverse portions along posterior margins of segments 3–7 light to medium brown, and ventral surface of segments 2–7 whitish gray with sternites 3–7 dark brown. Genitalia. Coxites, styles and ventral plate in ventral view as in Fig. 5 D. Coxite in ventrolateral view ( Fig. 5 E) nearly quadrate, 0.92 times as long as wide. Style in ventrolateral view ( Fig. 5 F) elongate, 1.5 times length of coxite, 2.4 times as long as its greatest width, somewhat sinuous, widened from base to basal one-fourth, narrowed to basal two-fifths, nearly parallel-sided to apical onefourth, then slightly narrowed toward round apex, and with stout subapical spine; style in medial view ( Fig. 5 G) flattened dorsoventrally, gradually narrowed toward apex, and without basal or subbasal protuberance. Ventral plate in ventral view ( Fig. 5 D) with body nearly rectangular, having ventrally produced median process that is bare except parts of lateral and anterior surfaces densely covered with minute setae, and is furnished with several teeth in vertical row on each posterolateral margin; basal arms short, stout and divergent; ventral plate in lateral view ( Fig. 5 H) with body and its ventrally produced process with rounded ventral apex, with dentate posterior margin, and densely covered with minute setae anteromedially and anterolaterally; ventral plate in caudal view ( Fig. 5 I) with body and ventrally produced median process slightly narrowed from base to basal one-third, nearly parallelsided to apical one-third, then tapered apically, bare, with several teeth in vertical row on each lateral margin. Median sclerite in lateral view ( Fig. 5 H) folded backward and then curved dorsally, and in caudal view ( Fig. 5 J) plate-like, somewhat pigmented except medioapical portion unpigmented, somewhat widened to middle, then somewhat narrowed toward apex. Paramere ( Fig. 5 K) wide basally and with several parameral hooks apically. Aedeagal membrane ( Fig. 5 L) densely covered with minute setae, without sclerotized dorsal plate. Ventral surface of tenth abdominal segment ( Fig. 5 M, N) without distinct hairs. Cercus ( Fig. 5 M, N) rounded posteriorly, with 13 or 14 distinct hairs.

Pupa. Body length (excluding gill filaments) 3.4–3.6 mm. Head. Integument yellowish, densely covered with round tubercles; frons with two unbranched short trichomes ( Fig. 6 A) on each side; face with one unbranched or bifid long trichome ( Fig. 6 B) on each side; frontal trichomes much shorter than facial ones. Thorax. Integument yellowish, densely covered with round tubercles on dorsal and lateral surfaces on anterior half, and moderately covered with cone-shaped smaller tubercles on dorsal surface of posterior half, except lateral surface of posterior one-fourth and most of anterior half of wing sheath on each side almost bare; thorax with two medium-long stout anterodorsal trichomes ( Fig. 6 C), two medium-long anterolateral trichomes (one slender, one stout) ( Fig. 6 D), one medium-long stout mediolateral trichome ( Fig. 6 E), and three ventrolateral trichomes (two long and stout, one short and slender) ( Fig. 6 F), on each side; all unbranched. Gill ( Fig. 6 G) with six slender thread-like filaments in pairs; all pairs sessile; all filaments subequal in length (1.2–1.3 mm) to one another; relative thickness of filaments from dorsal to ventral when compared basally 1.00:0.94:1.00:0.82:0.94:0.82; upper filament of each pair always slightly thicker than counter lower filament; each filament light to medium brown, gradually tapered toward apex; upper filament of dorsal pair and lower filament of ventral pairs at angle of 90 degrees when their basal portions were viewed laterally; cuticular surface with marked annular ridges and furrows in regular intervals throughout their length, covered with minute tubercles. Abdomen. Dorsally, segment 1 yellow, other segments unpigmented; segment 1 with 3–20 minute tubercles near lateral margin and with one unbranched short slender seta ( Fig. 6 H) on each side; segment 2 with one unbranched short slender seta and five minute setae, of which four are stout and pigmented, one is slender and unpigmented ( Fig. 6 I), on each side; segments 3 and 4 each with four unbranched hooked spines and one minute slender seta on each side; segments 5, 6, 7 and 9 without spine-combs; segment 8 with spine-combs and comb-like groups of minute spines in transverse row on each side; segment 9 without terminal hooks. Ventral surface as in S. (S.) crassimanum . Cocoon ( Fig. 6 J, K). Shoe-shaped, with relatively high anterior collar having small depressed portion medially, thickly woven, ochreous, not extended ventrolaterally; individual threads invisible; 4.3–4.5 mm long by 1.5 mm wide.

Specimens examined. Two females, one male, one pupal exuviae, collected from a small stream (width 0.2 m, depth 2–3 cm, streambed sandy, water temperature 16.4˚C, shaded, altitude 1,728 m, 06˚01.397’ N/116˚32.661’ E), slow flowing in a natural forest, Timpohon, Mt. Kinabalu, Sabah, 20-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 10–15 m, depth 0.5 m, exposed to the sun) just below the Park Office of Mesilau, 11-IX-2007, by H. Takaoka.

Ecological notes. The pupae of this species were collected from trailing grasses and dead leaves of trees in the water. No associated species was found.

Distribution. Sabah.

Remarks. The lectotype of S. (S.) laterale was in bad condition with all flagellomeres of the antennae, fore leg (both sides), midleg (one side), hind leg (one side) and wing (one side) missing and one wing dropped on the label, but it was useful for confirming the following characteristics: scape and pedicel dark brown, hind tibia entirely dark brown to black, hind basitarsus whitish on the basal half and slightly more, and basal portion of radial vein entirely bare. The paralectotype female was in good condition, with the scape, pedicel and the base of the first flagellomere orange-yellow, fore tibia dark brown with a large white portion on the outer surface, mid basitarsus mostly yellowish except the apical tip darkened, hind tibia dark brown to black with the base yellow, hind basitarsus yellowish on the basal two-thirds and slightly more, and basal portion of the radial vein entirely bare.

These results indicate that the lectotype and paralectotype specimens are different from each other, and both specimens are distinct from the female specimen that Smart and Clifford had thought to be S. (S.) laterale because the latter has the haired basal portion of the radial vein ( Smart and Clifford 1969). The entirely dark hind tibia combined with the bare basal portion of the radial vein of the lectotype female of S. (S.) laterale is in good agreement with that of the female of S. (S.) kinabaluense (legs shown in figure 17E on page 44 of Smart and Clifford 1969). In addition, the mid basitarsus of S. (S.) kinabaluense illustrated is yellowish on the basal half, as noted in the original description of S. (S.) laterale by Edwards (1933). The leg color of the paralectotype female of S. (S.) laterale is similar to that of the lectotype female of S. (S.) crassimanum , which was originally described from females collected at Kamborangah in the Kinabalu National Park ( Edwards 1933).

The male and pupa of S. (S.) laterale are morphologically indistinguishable from those of S. (S.) kinabaluense except the number of male upper-eye facets, which are in 17–19 vertical columns and 18–20 horizontal rows in S. (S.) laterale and in 15 or 16 vertical columns and 14–16 horizontal rows in S. (S.) kinabaluense ( Smart and Clifford 1969) . More males are required to judge whether this numerical difference represents interspecific or intraspecific variation. Here, S. (S.) kinabaluense is synonymized with S. (S.) laterale .

Figures

FIGURE 4. Female of Simulium (Simulium) laterale. (A) and (B) Third segments of maxillary palp with sensory vesicle (front view; A, right side; B, left side). (C) Cibarium. (D) Basitarsus and second tarsomere of hind leg (left side; outer view). (E) Claw. (F) Posterior tip of abdomen showing sternite 8 and ovipositor valves (ventral view). (G) Ovipositor valve (right side; anteroventral view). (H) Genital fork (ventral view). (I) Paraproct and cercus (right side; lateral view). (J) Spermatheca. Scale bars. 0.1 mm for D; 0.02 mm for A – C, E – J.

FIGURE 5. Male of Simulium (Simulium) laterale. (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 (right 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 6. Pupa of Simulium (Simulium) laterale. (A) Frontal trichomes. (B) Facial trichomes. (C) – (F) Thoracic trichomes (C, anterodorsal; D, anterolateral; E, mediolateral; F, ventrolateral). (G) Anterior half of thorax and gill filaments (left side; outer view). (H) Slender short seta on dorsal surface of abdominal segment 1. (I) Slender short seta, minute stout seta and minute fine seta on dorsal surface of abdominal segment 2. (J) and (K) Cocoons (J, dorsal view; K, lateral view). Scale bars. 1.0 mm for J and K; 0.1 mm for G; 0.02 mm for A – F, H and I.