Simulium malyschevi

Takaoka, Hiroyuki, Sofian-Azirun, Mohd, Ya’Cob, Zubaidah, Chen, Chee Dhang, Lau, Koon Weng, Low, Van Lun, Pham, Xuan Da & Adler, Peter H., 2017, The black flies (Diptera: Simuliidae) of Vietnam, Zootaxa 4261 (1), pp. 1-165 : 101-108

3) Simulium malyschevi species-group

Simulium (Simulium) obliquum Takaoka & Low sp. nov.

Female. Body length 2.0– 2.3 mm. Head. Narrower than thorax. Frons black, shiny, with several dark long stout hairs along each lateral margin and few similar hairs just above lower margin; frontal ratio 1.3:1.0:1.0; frons:head ratio 1.0:3.2. Fronto-ocular area well developed, short, directed laterally and slightly upward. Clypeus black, white pruinose, moderately covered with dark long stout hairs along lateral and ventral margins and middle portion of upper two-thirds widely bare. Labrum 0.7 times as long as clypeus. Antenna composed of scape, pedicel and nine flagellomeres, medium to dark brown except scape, pedicel, and flagellomeres 1 and 2 yellow when viewed anteriorly or ventrally, and medium to dark brown except scape and pedicel and base of flagellomere 1 yellow, and rest of flagellomere 1 dark yellow to light brown when viewed posteriorly or dorsally. Maxillary palp with five segments, light brown; proportional lengths of third, fourth, and fifth segments 1.0:1.1:2.0–2.2; third segment ( Fig. 44 A) of normal size; sensory vesicle ( Fig. 44 A) small, ellipsoidal (0.2 times length of third segment) having moderate opening. Maxillary lacinia with 9–12 inner and 12–14 outer teeth. Mandible with 21–26 inner and 11–13 outer teeth. Cibarium ( Fig. 44 B) with blunt median projection bearing several minute tubercles on posterior margin and with three or four minute pointed processes near posterior margin on each side. Thorax. Scutum black, unpatterned, shiny, thinly white pruinose when illuminated at certain angles, moderately covered with dark recumbent minute hairs intermixed with several dark-brown long upright hairs on prescutellar area. Scutellum black, white pruinose when illuminated at certain angles, covered with dark-brown upright long hairs. Postnotum black, white pruinose when illuminated at certain angles, and bare. Pleural membrane bare. Katepisternum black, longer than deep, bare. Legs. Foreleg: coxa whitish yellow; trochanter yellow; femur deep yellow except apical cap medium brown; tibia ( Fig. 44 C) white except inner surface of base light brown, and apical cap dark brown, and with large white sheen on outer surface when illuminated at certain angles; tarsus brownish black, with moderate dorsal hair crest; basitarsus greatly dilated, 4.4–4.5 times as long as its greatest width. Midleg: coxa dark brown; trochanter medium brown except base yellowish white; femur medium brown with extreme base somewhat lighter; tibia ( Fig. 44 D) medium to dark brown with extreme base and basal one-third of posterior surface yellowish white (its border obliquely defined in lateral view), and with white sheen on posterior surface when illuminated at certain angles; tarsus ( Fig. 44 E) yellowish white except apical tip of basitarsus, apical one-third of second tarsomere and most of third tarsomere grayish, fourth tarsomere light brown, and fifth tarsomere medium brown. Hind leg: coxa dark brown; trochanter yellowish white; femur dark brown except base yellowish white and apical cap brownish black; tibia ( Fig. 44 F) medium to dark brown except base and little less than basal half of posterior surface yellowish white (its border obliquely defined in lateral view) and apical cap brownish black; tarsus ( Fig. 44 G) yellowish white except apical one-fourth or little more of basitarsus medium brown, and apical one-third of second tarsomere and most of third tarsomere grayish, and whole of fourth tarsomere light brown, and fifth tarsomere medium brown; basitarsus ( Fig. 44 G) parallel-sided, 6.0–7.2 times as long as wide, and 0.7 and 0.6 times as wide as greatest widths of hind tibia and femur, respectively; calcipala ( Fig. 44 G) developed, small, little shorter than its basal width, and 0.4 times as wide as greatest width of basitarsus; pedisulcus ( Fig. 44 G) well developed at basal two-fifths of second tarsomere; claw ( Fig. 44 H) with small subbasal tooth. Wing. Length 1.9–2.0 mm. Costa with dark spinules and dull hairs; subcosta bare (except one female with one and two hairs on each subcosta); basal section of radius bare; R1 with dark spinules and hairs; R2 with hairs; hair tuft on base of radium dark brown; basal cell absent. Halter . White except base light brown. Abdomen. Basal scale medium brown, with fringe of dull hairs. Dorsal surface of abdomen medium to dark brown, with short dark hairs; tergite 2 brightly iridescent when illuminated at certain angles, and tergites 6–9 shiny. Ventral surface of segment 7 ( Fig. 44 I) with 46–51 branched stout dark hairs medially. Terminalia . Sternite 8 ( Fig. 44 J) bare medially, with 8–11 dark medium-long to long stout hairs and three yellow short hairs on each lateral surface. Ovipositor valve ( Fig. 44 J) flap-like, bluntly truncate posteriorly, forming oblique roof-like ridge parallel to posterior margin running obliquely, thin, membranous, covered with five to eight dark medium-long or long hairs, one to eight yellow short hairs and numerous microsetae; inner margins not sclerotized, moderately concave medially and widely separated from each other. Genital fork ( Fig. 44 K, L) of inverted-Y form, with narrow well sclerotized stem; arms of moderate width, each with distinct projection with rounded apex directed anterodorsally and triangular projection-like sclerotized posteromedial corner. Paraproct in ventral view ( Fig. 44 M) triangular, pointed medially, with unpigmented shallow depression on ventral surface along anteromedial margin; anteromedial surface moderately sclerotized and with 6– 12 sensilla; paraproct in lateral view ( Fig. 44 N) 0.6 times as long as wide, with unpigmented shallow depression narrowing ventrally along anteroventral margin, somewhat protruding beyond ventral margin of cercus, and with 10–12 hairs on ventral and lateral surfaces. Cercus in lateral view ( Fig. 44 N) short, rounded posteriorly, 0.43 times as long as wide, and with numerous short to medium-long hairs. Spermatheca ( Fig. 44 O) large, nearly ovoid, 1.3 times as long as wide, well sclerotized except portion of juncture with duct unsclerotized, with weakly defined surface patterns near base, and with internal setae; accessory ducts subequal in thickness to each other, and to major duct.

Male. Body length 2.1–2.3 mm. Head. wider than thorax. Upper eye consisting of large facets in 16–18 vertical columns and in 16–18 horizontal rows. Clypeus brownish black, thickly white pruinose and brightly shiny when illuminated at certain angles, sparsely covered with dark brown hairs along and near lateral margins (most of central portion bare). Antenna composed of scape, pedicel and nine flagellomeres, dark brown to brownish black except scape and pedicel dark yellow, base of first flagellomere yellow, and rest of first flagellomere light brown; first flagellomere elongate, 1.5–1.7 times length of second one. Maxillary palp composed of five segments, light to medium brown except first and second segments grayish yellow; proportional lengths of third, fourth, and fifth segments 1.0:1.2–1.3:2.3; third segment ( Fig. 45 A, B) of normal size; sensory vesicle ( Fig. 45 A, B) globular or ellipsoidal, 0.1–0.2 times length of third segment, and with small opening. Thorax. Scutum black, with whitish pruinose pattern (brightly iridescent when illuminated at certain angles), i.e., anterior pair of large triangular spots with pointed posteromedial apex on shoulders, narrow band along each lateral margin and large transverse spot entirely covering prescutellar area, all these spots connected; scutum uniformly and moderately covered with brassy recumbent short hairs interspersed with dark-brown long upright hairs on prescutellar area. Scutellum black, with several dark-brown long upright hairs. Postnotum black, whitish pruinose (brilliantly iridescent when illuminated at certain angles) and bare. Pleural membrane bare. Katepisternum brownish black, bare. Legs. Color almost as in female except following characters: Fore tibia ( Fig. 45 C) medium brown except median outer surface white and apical cap dark brown. Fore basitarsus greatly dilated, 5.2–5.5 times as long as its greatest width. Mid femur entirely darkened. Mid and hind tibiae dark brown except base yellowish white. Hind basitarsus ( Fig.45 D) yellowish white except apical one-third medium brown, and slightly widened toward apical one-fourth, 5.0–5.2 times as long as wide, and 0.7–0.8 and 0.7–0.8 times as wide as greatest widths of hind tibia and femur, respectively; calcipala ( Fig. 45 D) developed, small, little shorter than its basal width, and 0.3 times as wide as greatest width of basitarsus; pedisulcus ( Fig. 45 D) well developed. Wing. Length 1.6 mm. Other characters as in female including bare subcosta. Halter . White except base light brown. Abdomen. Basal scale brownish-black, with fringe of dark-brown long hairs. Dorsal surface of abdomen dark brown to black, moderately covered with dark-brown short to medium-long hairs; segments 2, 5, 6 and 7 each with pair of whitish pruinose spots (brightly iridescent when illuminated at certain angles) dorsolaterally, those on segment 2 broadly connected in middle to each other. Genitalia. Coxites, styles and ventral plate in ventral view as in Fig. 45 E. Style in ventral view ( Fig. 45 E) elongate, with inner margin sinuous, with slender subapical spine; style in ventrolateral view ( Fig. 45 F) 1.9 times length of coxite, 2.8 times as long as greatest width near basal one-fourth; style in medial view ( Fig. 45 G) flattened dorso-ventrally except basal half gently produced dorsally, which is densely covered with fine short hairs.

Ventral plate in ventral view ( Fig. 45 E) Y-shaped, with body narrowed posteriorly; arms medium-long and stout, widely separated from each other; ventral plate in lateral view ( Fig. 45 H) with body slightly curved ventrally, and with serrated posterior margin; ventral plate in caudal view ( Fig. 45 I) with body parallel-sided and rounded ventrally, bare, with four teeth in each of two vertical rows on posterior surface. Median sclerite ( Fig. 45 H, J) weakly sclerotized, plate-like, wide, with blunt apical tip having incision medially. Paramere ( Fig. 45 K) with wide base having several hooks apically. Aedeagal membrane ( Fig. 45 K) moderately covered with minute setae; dorsal plate ( Fig. 45 L) horizontal bar-like, weakly sclerotized (except medial portion widely unsclerotized). Abdominal segment 10 ( Fig. 45 M, N) without distinct hairs on each side of posterior surface. Cercus ( Fig. 45 M, N) small, rounded, with six to eight hairs.

Pupa. Body length 2.2–2.4 mm. Head. Integument including antennal sheaths grayish yellow, bare except face sparsely covered with small round tubercles; antennal sheath without any ridges or projections; frons with two pairs of unbranched slender short trichomes arising close together ( Fig. 46 A); face with pair of unbranched short trichomes ( Fig. 46 B), much longer than frontal trichomes. Thorax. Integument grayish yellow to ochreous, bare on dorsal and dorsolateral surface of anterior half, and sparsely to moderately covered with small tubercles on dorsal, dorsolateral and lateral surfaces of posterior half; thorax on each side with two medium-long trichomes mediodorsally ( Fig. 46 C), two trichomes (one medium-long, one short) anterolaterally ( Fig. 46 D), one short trichome mediolaterally ( Fig. 46 E), and three trichomes (one medium-long, two short) ventrolaterally ( Fig. 46 F). Gill ( Fig. 46 G) composed of six thread-like short filaments arranged in three pairs (dorsal, middle and ventral) arising from short common basal stalk; each pair short-stalked; all filaments nearly subequal in length (1.0– 1.5 mm) to one another, though two filaments of ventral pair slightly shorter than others, and inner filament of middle pair slightly longer than outer filament of middle pair; each filament of same thickness (or slightly widened as in outer filaments of middle and ventral pairs) from base to basal one-third, then gradually tapered toward apex; relative thickness of six filaments from dorsal to ventral when measured basally 1.0:0.9–1.1:0.7–1.0:1.1–1.2:0.7– 0.8:0.8–0.9, inner filament of middle pair thickest and outer filament of ventral pair thinnest; all filaments medium to dark brown, with annular ridges and furrows, densely covered with minute tubercles. Abdomen. Dorsally, segment 1, basal half of segment 2 and narrow portion along anterior margin of segment 3 light brown, other segments transparent except basal areas of spine-combs on segments 7–9 yellow; segment 1 with one unbranched slender short seta ( Fig. 46 H) on each side; segment 2 with one unbranched short seta and five minute setae ( Fig. 46 I) on each side; segments 3 and 4 each with four distinct unbranched hooks and one unbranched minute seta on each side; segments 5 and 6 lacking spine-combs; segments 7–9 each with distinct spine-combs in transverse row and comb-like groups of minute spines, on each side; segment 9 without terminal hooks. Ventrally, segments 3–9 transparent, each (except segment 9) with comb-like groups of minute spines; segment 4 with few slender minute setae on each side; segment 5 with pair of bifid stout hooks submedially and few unbranched minute setae on each side; segments 6 and 7 each with pair of bifid inner and bifid outer stout hooks somewhat separated from each other, and few unbranched short setae on each side. Grapnel-shaped hooklets absent on each side of segment 9. Cocoon ( Fig. 46 J). Simple, wall-pocket-shaped, dull yellowish white, thinly woven, with large anterolateral window (rarely divided into two open spaces) on each side; posterior two-thirds with floor; individual threads invisible; 2.6–3.0 mm long by 1.0– 1.2 mm wide.

Mature larva. Body length 3.5–4.2 mm. Body color creamy with color markings as follows: thoracic segment 1 with grayish-green transverse band though disconnected medioventrally, grayish green on anterior surface of proleg (and usually faintly on posterior surface of proleg) (in three larvae, grayish-green portions mottled with reddish-brown pigment); thoracic segment 2 faintly grayish green on dorsal surface and grayish green mottled with reddish-brown pigment on ventral surface; thoracic segment 3 with faint to moderate reddish-brown transverse band on dorsal and dorsolateral surfaces, and grayish green mottled with reddish-brown pigment on ventral surface; abdominal segments 1–5 each with grayish-green transverse band mottled with reddish-brown pigment, though dorsomedially disconnected; abdominal segments 6–9 grayish green entirely or partially mottled with reddish-brown pigment on dorsal and dorsolateral surfaces and on ventral surface of segments 6 and 7, though dorsomedial portion of segments 7 and 8 often unpigmented; covering of reddish-brown pigment incomplete in some larvae so that one larva entirely light grayish green, and few larvae showing grayish-green ventral surface of abdominal segments 1–5. Head. Cephalic apotome ( Fig. 47 A) yellow except posterior half widely darkened medially leaving posterior one of mediolongitudinal spots and posterolateral spots pale, hence making these head spots negative; anterior spot of mediolongitudinal spots and mediolateral spots usually indistinct. Lateral surface of head capsule yellow except eye-spot region whitish and often somewhat darkened between eye-spot region and posterior margin; eyebrow not darkened or slightly darkened; spot below eye-spot region rarely recognized as positive, and large spots in front of posterior margin obscure. Ventral surface of head capsule ( Fig. 47 B) yellow except each side of basal portion of postgenal cleft dark brown, and often slightly darkened medially and posteriorly. Antenna composed of three articles and apical sensillum, slightly longer than stem of labral fan; length ratio of three articles (from base to tip) 1.0:1.1:0.8–0.9. Labral fan with 40–42 primary rays. Mandible ( Fig. 47 C) with mandibular serration composed of two teeth (one medium-sized, one small); main tooth at obtuse angle against mandible on apical side; supernumerary serrations absent; comb-teeth decreasing in length from first to third. Hypostoma ( Fig. 47 D) with nine anterior teeth, of which median and corner teeth subequal in length, and longer than three intermediate teeth on each side; lateral margins sharply serrate apically; four hypostomal bristles in row nearly parallel to lateral border on each side. Postgenal cleft ( Fig. 47 B) long, approaching posterior margin of hypostoma leaving narrow postgenal bridge. Thorax and Abdomen. Histoblast of pharate pupal gill with six short filaments. Thoracic and abdominal cuticle with distinct transverse striations and sparsely covered with minute colorless flattened setae and short unbranched colorless setae ( Fig. 47 E); abdominal segment 9 with 8–10 short unbranched colorless setae on each side of anal sclerite; thoracic segment 3 with two small protuberances (one dorsally and one dorsolaterally) on each side; abdominal segments 1–4 each with six small protuberances (one dorsally, one dorsolaterally, two laterally, one ventrolaterally, and one ventrally) on each side; abdominal segment 5 with four small protuberances (one dorsally, one dorsolaterally, two laterally), abdominal segment 6 with three small protuberances (one dorsally, one dorsolaterally and one laterally) on each side; abdominal segment 7 with two small protuberances (one dorsally and one dorsolaterally) on each side; abdominal segment 8 with one small protuberance dorsally on each side; all protuberances cone-shaped except ventral ones rounded ( Fig. 47 F). Rectal scales present. Rectal organ compound, each lobe with 9 or 10 finger-like secondary lobules. Anal sclerite Xshaped, widely sclerotized basally, with short broad anterior arms 0.7 times as long as posterior ones, and four to eight sensilla posterior to posterior arms. Last abdominal segment bulged ventrolaterally but lacking ventral papillae. Posterior circlet with 70–74 rows of hooklets with up to 13 or 14 hooklets per row.

Type material. HOLOTYPE: Female (with its associated pupal exuviae and cocoon) in 80% ethanol, labeled in a vial as [ UMSRP: Vietnam 0 37, Holotype, Simulium (S.) obliquum , Female, coll. Vietnam, 9-XII-2015, Takaoka et al.], reared from pupa collected from a river (width 8–10 m, flow moderate, bottom of pebbles, water temperature 17˚C, exposed to the sun, elevation 162 m, 18˚58’45.918”N/109˚50’10.693”E), fast flowing in a natural forest, Pu Mat , Nghe An Province, northern Vietnam , 9-XII-2015, H. Takaoka, M. Sofian-Azirun, C.D. Chen, & K.W. Lau. PARATYPES: 15 females and 15 males, with their associated pupal exuviae and cocoons, and 10 mature larvae, in 80% ethanol, same data as those of the holotype labeled in each vial as [ UMSRP: Vietnam 0 37, Paratype, Simulium (S.) obliquum , Female, coll. Vietnam, 9-XII-2015, Takaoka et al.].

Biological notes. The pupae and larvae of S. (S.) obliquum sp. nov. were collected from grasses trailing in the current. Associated species were S. (S.) tani (complex) and S. (S.) sp. ( S. striatum species-group).

Distribution. Vietnam (Nghe An).

Etymology. The specific name obliquum refers to the ovipositor valve with a slanting posterior margin. The Latin adjective ‘obliquus’ means slanting.

Remarks. Simulium (S.) obliquum sp. nov. is assigned to the S. malyschevi species-group of the subgenus Simulium , defined by Rubtsov (1956), in having the female claw with a small subbasal tooth ( Fig. 44 H), ovipositor valve with the posterior margin oblique ( Fig. 44 J), male style without a basal or subbasal projection ( Fig. 45 G), and ventral plate Y-shaped (ventral view), with a toothed posterior margin ( Fig. 45 E).

This new species is similar in the pupa and larva to S. (S.) siripoomense Takaoka & Saito described based on the pharate female, pupae and larvae collected in Thailand ( Takaoka and Saito 1996; Takaoka and Mulla 2000). However, this new species is distinguished from S. (S.) siripoomense in the female by the length ratio of the sensory vesicle against the third maxillary palpal segment ( Fig. 44 A) (0.2 in this new species but 0.4 in S. (S.) siripoomense ), and in the larva by the postgenal cleft not reaching the posterior border of the hypostoma ( Fig. 47 B) (widely reaching the posterior border of the hypostoma in S. (S.) siripoomense ).

This new species is also similar to S. (S.) hirtipanus Puri , which was described from the female, male and pupa collected from India ( Puri 1932c). This new species differs from the latter species by the following characters (those of S. (S.) hirtipanus in parentheses): in the female by the frons:head ratio 1.0:3.2 (1.0:2.0), hind trochanter yellowish white (black), genital fork with a strongly sclerotized projection-like posteromedial corner ( Fig. 44 K) (without such sclerotized corner), and the paraproct covered with 10–12 stout hairs (18 stout hairs); in the male by the hind trochanter yellowish white (black); and in the pupa by the presence of spine-combs on abdominal segment 9 (absent). This species is distinguished from other related species of the S. malyschevi species-group, which have a cluster of branched stout hairs on female abdominal segment 7 and a pupal gill with six filaments, by the larval abdomen with multiple pairs of protuberances ( Fig. 47 F).

Figures

FIGURE 44. Female of Simulium (Simulium) obliquum sp. nov. A, Third segment of maxillary palp with sensory vesicle (right side; front view); B, Cibarium (front view); C, Fore tibia (left side; outer view); D, Mid tibia (left side; outer view); E, Mid tarsus (left side; outer view); F, Hind tibia (left side; outer view); G, Hind tarsus (left side; outer view). H, Claw; I, Abdominal segment 7 showing cluster of branched hairs; J, Sternite 8 and ovipositor valve (right side only; ventral view); K & L, Genital forks (K, ventral view; L, lateral view); M & N, Paraprocts and cerci (M, ventral view; N, lateral view). O, Spermatheca. Scale bars. 0.1 mm for C – G; 0.02 mm for A, B and I – O; 0.01 mm for H.

FIGURE 45. Male of Simulium (Simulium) obliquum sp. nov. A & B, Third segments of maxillary palps with different shape of sensory vesicles (right side; front view); C, Fore tibia (left side; outer view); D, Hind basitarsus and second tarsomere (left side; outer view); E, Coxites, styles and ventral plate (ventral view); F & 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 and aedeagal membrane (left side; caudal view); L, Dorsal plate (caudal view); M & N, Abdominal segment 10 and cerci (right side; M, lateral view; N, caudal view). Scale bars. 0.1 mm for C and D; 0.02 mm for A, B and E – N.

FIGURE 46. Pupa of Simulium (Simulium) obliquum sp. nov. A, Frontal trichomes; B, Facial trichome; C – F, Thoracic trichomes (C, anterodorsal; D, anterolateral; E, mediolateral; F, ventrolateral); G, Anterior part of thorax and gill filaments (left side; outer view); H, Hair-like seta and minute seta on dorsal surface of abdominal segment 1; I, Hair-like seta, minute seta and stout seta on dorsal surface of abdominal segment 2; J, Cocoon (lateral view). Scale bars. 0.5 mm for J; 0.1 mm for G; 0.02 mm for A – F; 0.01 mm for H and I.

FIGURE 47. Larva of Simulium (Simulium) obliquum sp. nov. A & B, Head capsules (A, dorsal view; B, ventral view); C, Mandible; D, Hypostoma; E, Transverse striations, dorsal protuberance and minute setae on dorsal surface of abdominal segment 5; F, Entire body showing protuberances (lateral view). Scale bars. 0.5 mm for F; 0.2 mm for A and B; 0.02 mm for C, D and E.