Simulium (Simulium) lacduongense Takaoka

Takaoka, Hiroyuki, Sofian-Azirun, Mohd, Ya’Cob, Zubaidah, Chen, Chee Dhang, Lau, Koon Weng & Pham, Xuan Da, 2015, The black flies (Diptera: Simuliidae) from Thua Thien Hue and Lam Dong Provinces, Vietnam, Zootaxa 3961 (1), pp. 1-96 : 60-66

Simulium (Simulium) lacduongense Takaoka & Ya’cob sp. nov.

( Figs. 25 A–27J)

Female. Body length 3.0 mm. Head. Narrower than thorax. Frons black, shiny, with several dark long stout hairs along each lateral margin and four similar hairs just above lower margin; frontal ratio 1.4:1.0:1.6; frons:head ratio 1.0:4.6. Fronto-ocular area well developed, short, directed laterally and slightly upward. Clypeus black, white pruinose, slightly shiny when illuminated at certain angles, moderately covered with dark-brown long stout hairs along lateral and ventral margins and middle portion widely bare. Labrum 0.69 times as long as clypeus. Antenna composed of scape, pedicel and nine flagellomeres, medium to dark brown except scape, pedicel, base of first flagellomere and ventral surface of flagellomeres 1 and 2 yellow. Maxillary palp with five segments, proportional lengths of third, fourth, and fifth segments 1.0:1.1:2.7; third segment ( Fig. 25 A) of normal size; sensory vesicle ( Fig. 25 A) of moderate size, (0.33–0.41 times length of third segment) having large opening near apex. Maxillary lacinia with 12 or 13 inner and 13 or 14 outer teeth. Mandible with 24 or 25 inner and 14 outer teeth. Cibarium ( Fig. 25 B) with blunt medial projection on posterior margin and without minute processes near base of medial projection. Thorax. Scutum black, shiny when illuminated at certain angles, densely covered with golden-yellow recumbent short hairs interspersed with several dark-brown long upright hairs on prescutellar area; when illuminated in front and viewed dorsally, scutum white pruinose, with five longitudinal non-pruinose vittae (one narrow medial vitta, two wider submedial vittae and two wider sublateral vittae though sublateral vittae somewhat wider than submedial ones), all vittae united with broad transverse band on prescutellar area; when illuminated from behind, scutum having reversed color pattern. Scutellum brownish-black, covered with dark-brown upright long hairs and golden-yellow short hairs. Postnotum black, white pruinose when illuminated at certain angles and bare. Pleural membrane bare. Katepisternum longer than deep, black, shiny and white pruinose when illuminated at certain angles and bare. Legs. Foreleg: coxa whitish-yellow; trochanter whitish-yellow to yellow; femur yellow except apical cap medium brown on front surface, light brown except little more than basal two-fifths yellow and apical cap medium brown on posterior surface; tibia white except apical cap black, with shiny sheen widely on outer surface when illuminated at certain angles; tarsus black, with moderate dorsal hair crest; basitarsus greatly dilated, 4.9 times as long as its greatest width. Midleg: coxa black; trochanter light brown; femur medium brown except base yellow and apical cap dark brown; tibia white except apical cap dark brown, and with shiny sheen on posterior surface when illuminated at certain angles; tarsus dark brown except little more than basal half of basitarsus whitish. Hing leg: coxa black; trochanter yellow; femur brownish-black except basal one-fourth yellow and apical cap black; tibia white except apical cap dark brown, and with shiny sheen on posterior surface when illuminated at certain angles; tarsus brownish-black except little less than basal two-thirds of basitarsus and basal one-third of second tarsomere whitish; basitarsus ( Fig. 25 C) nearly parallel-sided, 5.96 times as long as wide, and 0.77 and 0.63 times as wide as greatest widths of hind tibia and femur, respectively; calcipala ( Fig. 25 C) moderately developed, slightly shorter than basal width, and 0.35 times as wide as basitarsus; pedisulcus ( Fig. 25 C) well developed at basal one-third of second tarsomere; all tarsal claws simple. Wing. Length 2.0 mm. Costa with dark spinules and hairs; subcosta haired except near apex bare; basal section of radial vein fully haired; R1 with dark spinules and hairs; R2 with hairs; hair tuft on base of radial vein dark brown; basal cell absent. Halter . White with basal portion darkened. Abdomen. Basal scale medium brown, with fringe of dark-brown long hairs. Dorsal surface of abdomen brownish-black except basal half of second segment yellowish-white, with short dark hairs; tergite 2 shiny, white iridescent when illuminated at certain angles, and tergites 6–8 shiny. Genitalia. Sternite 8 ( Fig. 25 D) bare medially, with 26–29 dark medium-long to long stout hairs on each lateral surface. Ovipositor valves ( Fig. 25 D) triangular though rounded posteomedially, membranous, each moderately covered with microsetae, one dark medium-long hair and one unpigmented short hair, except portion along inner margin widely bare, so thin and transparent that it is difficult to discern inner margins. Genital fork ( Fig. 25 E) of inverted-Y form, with narrow well sclerotized stem; arms of moderate width, each with distinct short and wide projection having pointed apex directed anterodorsally. Paraproct in ventral view ( Fig. 25 F) nearly quadrate, densely covered with minute setae and with 36 or 37 short to medium-long hairs on lateral and ventral surfaces except anterolateral corner widely unpigmented and bare; anteromedial surface with four or five short sensilla; paraproct in lateral view ( Fig. 25 G) moderately protruded ventrally beyond ventral margin of cercus. Cercus in lateral view ( Fig. 25 G) short, rounded posteriorly, 0.36 times as long as wide, and with numerous short to medium-long hairs. Spermatheca ( Fig. 25 H) large, nearly ovoid, 1.2 times as long as wide, well sclerotized except portion of juncture with duct unsclerotized, with no defined surface patterns, and with internal setae; accessory ducts subequal in thickness to each other, and to major duct.

Male. Body length 3.5 mm. Head. Width subequal to that of thorax. Upper eye medium brown, consisting of large facets in 19 vertical columns and in 20 horizontal rows. Clypeus black, thickly white pruinose, silvery or bluish, shiny when illuminated at certain angles, sparsely covered with dark-brown hairs along and near lateral margins (most of central portion of upper half bare). Antenna composed of scape, pedicel and nine flagellomeres, medium to dark brown except scape, pedicel, and base of first flagellomere yellow though apical portion of pedicel dark yellow; first flagellomere elongate, 1.9 times as long as second one. Maxillary palp grayish to dark brown, composed of five segments with proportional lengths of third, fourth, and fifth segments 1.0:1.1:2.7; third segment ( Fig. 26 A) of moderate size; sensory vesicle ( Fig. 26 A) small (0.18 times length of third segment), ellipsoidal, and with opening of moderate size. Thorax. Scutum black, with white pruinose pattern, i.e., anterior pair of rectangular spots on shoulders extending posteriorly along lateral margins and connected to large transverse spot entirely covering prescutellar area; these pruinose areas shiny and iridescent when illuminated at certain angles; scutum uniformly and densely covered with golden-yellow recumbent short hairs interspersed with dark-brown long upright hairs on prescutellar area. Scutellum brownish-black, with several dark long upright hairs and goldenyellow short hairs. Postnotum black, white pruinose when illuminated at certain angles and bare. Pleural membrane bare. Katepisternum longer than deep, brownish-black to black, shiny and white pruinose when illuminated at certain angles, and bare. Legs. Foreleg: coxa whitish-yellow; trochanter dark brown except base yellowish; femur medium brown with apical cap dark brown; tibia medium to dark brown except outer surface widely white medially, and with white sheen when illuminated at certain angles; tarsus brownish-black, with moderate dorsal hair crest; basitarsus moderately dilated, 6.1 times as long as its greatest width. Midleg: coxa brownish-black to black; trochanter dark brown though extreme base yellow; femur dark brown; tibia whitish on basal half, and light to medium brown on rest except apical cap dark brown; tarsus dark brown except basal half of basitarsus light brown. Hind leg: coxa brownish-black to black; trochanter yellow; femur medium brown except base yellow and apical cap brownish-black; tibia dark brown to brownish-black except basal tip yellow; tarsus ( Fig. 26 B) dark brown to brownish-black except little more than basal half of basitarsus dark yellow or grayish yellow (basitarsus fully covered with black hairs, then border not well defined) and basal half of second tarsomere whitish; basitarsus ( Fig. 26 B) much enlarged, spindle-shaped, gradually widened from base to apical one-third, then tapered to apex, 4.38 times as long as its greatest width, and 0.81 and 0.87 times as wide as greatest widths of hind tibia and femur, respectively; calcipala ( Fig. 26 B) small, 0.63 times as long as width at base, 0.31 times as wide as greatest width of basitarsus; pedisulcus ( Fig. 26 B) well developed. Wing. Length 2.3 mm. Other features as in female except subcosta and basal section of radial vein bare. Halter . White with basal portion darkened. Abdomen. Basal scale dark brown to brownish-black, with fringe of dark long hairs. Dorsal surface of abdomen brownish-black to black except basal one-third of segment 2 yellowish, and covered with dark short hairs; segments 2 and 5–7 each with pair of silvery or bluish iridescent spots dorsolaterally, those on segment 2 connected broadly to each other in middle. Genitalia. Coxite in ventral view ( Fig. 26 C) nearly quadrate, covered with many stout hairs on posterior one-third; coxite in ventrolateral view ( Fig. 26 D) rectangular, 0.7 times as long as width. Style in ventral view ( Fig. 26 C) elongate, gradually tapered to middle, then nearly parallel-sided to apex, with apical spine; style in ventrolateral view ( Fig. 26 D) elongate, 3.1 times as long as its greatest width at base, nearly parallel-sided from base to basal one-third, then abruptly narrowed, and again nearly parallel-sided toward apex; style in medial view ( Fig. 26 E) spatulate dorsoventrally, 1.6 times as long as coxite, with long horn-like basal protuberance, with several minute cone-like spines each having microseta at its apex, on anterior surface, and with apical spine having two apices. Ventral plate in ventral view ( Fig. 26 C) with body nearly rectangular (though somewhat narrowed basally, and rounded on each posterolateral corner), with ventromedial process covered with many minute setae on anterior and anterolateral surfaces, and several ridges in two vertical rows on posterior surface; arms directed forward and divergent from each other; ventral plate in lateral view ( Fig. 26 F) having ventromedial process at about right or slightly greater angle against dorsal margin of body, with serrated posterior margin, and bare except anteroventral surface moderately covered with microsetae; ventral plate in caudal view ( Fig. 26 G) having ventromedial process parallel-sided except basal portion somewhat constricted and apical one-third narrowed toward tip, with rounded bare apex and having several ridges in two vertical rows on posterior surface except apical two-fifths without ridges, and no microsetae on posterior surface. Median sclerite ( Fig. 26 F, H) plate-like, widened from base toward apex, with round apex, brown basally, but not so well sclerotized apically. Paramere ( Fig. 26 I) with several distinct hooks. Aedeagal membrane densely covered with minute spinous setae, and with weakly sclerotized dorsal plate in form of horizontal bar ( Fig. 26 J). Abdominal segment 10 ( Fig. 26 K, L) without distinct hair on ventral and lateral surfaces. Cercus ( Fig. 26 K, L) small, rounded, with 10 distinct hairs.

Pupa. Body length 3.0 mm. Head. Integument ochreous, densely and elaborately covered with small round tubercles; antennal sheath bare except basal portion covered with small tubercles; frons with pair of unbranched slender short trichomes with uncoiled apices, or pair of bifid slender short trichome and unbranched slender short trichome ( Fig. 27 A) on each side; face with unbranched medium-long trichome with uncoiled apex ( Fig. 27 B) on each side. Thorax. Integument dark yellow to ochreous, densely and elaborately covered with small round tubercles; thorax on each side with three anterodorsal trichomes with uncoiled apices (anterior and middle trichomes bifid or trifid, medium-long or long, posterior trichome unbranched, short or medium-long or long) ( Fig. 27 C), two anterolateral trichomes (anterior trichome unbranched, medium-long or long, with uncoiled apex, posterior trichome unbranched or bifid, long, with coiled or uncoiled apex) ( Fig. 27 D), one unbranched mediumlong stout mediolateral trichome with uncoiled apex ( Fig. 27 E), and three ventrolateral trichomes (one short, slender, unbranched or bifid, two others unbranched or bifid or quadrifid, short or medium-long or long, stout) ( Fig. 27 F). Gill ( Fig. 27 G) with eight slender thread-like short filaments in four pairs (one dorsal, two middle and one ventral) arising from short common basal stalk; all pairs short-stalked; gill filaments widely divergent basally, upper filament of dorsal pair forming an obtuse angle of about 120 degrees against lower filament of ventral pair when viewed laterally; filaments slightly shortened from dorsal to ventral, with upper filament of dorsal pair longest (about 1.7 mm long), and lower filament of ventral pair shortest (about 1.0 mm long); relative thickness of eight filaments from dorsal to ventral when basal portions were compared 1.00:0.87–0.90:0.72–0.80:0.67–0.70: 0.75–0.77:0.69–0.70:0.50–0.63:0.58; all filaments medium to dark brown, tapered toward apex, with distinct annular ridges and furrows forming definite reticulate surface patterns, and densely covered with minute tubercles. Abdomen. Dorsally, segment 1 and basal half of segment 2 dark grayish, and other segments unpigmented except basal portions of spine-combs on segment 8 yellow; segment 1 with one unbranched slender short seta ( Fig. 27 H) on each side; segment 2 with one unbranched slender short seta and five short setae, of which three are much stouter than two others ( Fig. 27 I), on each side; segments 3 and 4 each with four distinct hooked spines and one unbranched short seta on each side; segment 8 with distinct spine-combs in transverse row on each side; segments 5, 6, 7 and 9 lacking spine-combs; segments 5–9 each with comb-like groups of minute spines on each side; segment 9 without terminal hooks. Ventrally, segments 3–9 unpigmented, each (except segment 9) with comb-like groups of minute spines; segment 4 with few unbranched slender minute setae on each side; segment 5 with pair of bifid stout hooks submedially and few unbranched short setae on each side; segments 6 and 7 each with pair of bifid inner and unbranched 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. 27 J). Wall-pocket-shaped or shoe-shaped with narrow anteroventral collar, tightly and thickly woven, ochreous, with medium-sized anterolateral window on each side, and not extended ventrolaterally; individual threads invisible; 3.6–3.8 mm long by 1.2 mm wide.

Mature larva. Unknown.

Type material. HOLOTYPE: Female, reared from a pupa collected from a small shallow stream (width 3–6 m, depth 10–20 cm, bottom sandy, water temperature 20.0˚C, exposed to the sun, altitude 1,440 m) (12˚08’32.409” N/108˚38’58.318” E) slowly flowing in open land, Da Chais, Lac Duong, Lam Dong Province, southern Vietnam, 24-IV-2014, H. Takaoka, M. Sofian-Azirun, Z. Ya’cob, C.D. Chen & K.W. Lau. PARATYPES: One male and two pupal exuviae and cocoons, same data as those of the holotype.

Biological notes. The pupae of S. (S.) lacduongense sp. nov. were collected from grass leaves and roots trailing in the water. Associated species were S. (G.) dachaisense sp. nov. and S. (S.) nodosum .

Etymology. The species name lacduongense refers to the district name, Lac Duong, where this new species was collected.

Remarks. Simulium (S.) lacduongense sp. nov. is assigned to the S. multistriatum species-group of the subgenus Simulium , defined by Takaoka and Davies (1996), based on the female scutum with five longitudinal vittae, female ovipositor valves thin and unpigmented along inner margins ( Fig. 25 D), male style with elongate basal protuberance ( Fig. 26 E), pupal gill with eight filaments ( Fig. 27 G), and cocoon with an anterolateral window on each side ( Fig. 27 J). This new species is characterized by the haired basal portion of the radial vein of the female wing, a character found in three species of the group: i.e., S. (S.) fenestratum Edwards originally described from Sumatra ( Edwards 1934), S. (S.) hirtinervis Edwards originally described from Peninsular Malaysia ( Edwards 1928), and S. (S.) sakishimaense Takaoka from Japan ( Takaoka 1977). However, S. (S.) fenestratum differs from this new species by the male style lacking minute cone-like spines on its basal protuberance, and the pupal gill filaments divergent at an angle of less than 90 degrees. Simulium (S.) hirtinervis differs by the number of male upper-eye facets in 14 vertical columns and 13 horizontal rows, and the ventromedial process of the ventral plate much constricted basally when viewed posteriorly. Simulium (S.) sakishimaense differs by the basal portion of the female radial vein partially haired only near its apex, male upper-eye large facets in 15 horizontal rows, style concave medially on both margins when viewed ventrolaterally, and gill filaments divergent at an angle of less than 90 degrees.

The pupal gill filaments divergent at an angle of more than 90 degrees ( Fig. 27 G) is similar to the condition in S. (S.) barraudi Puri , S. (S.) dentatum Puri , S. (S.) digitatum Puri , and S. (S.) novolineatum Puri , all originally described from India ( Puri 1932b, 1933), S. (S.) deothangense Takaoka & Somboon from Bhutan ( Takaoka and Somboon 2008), S. (S.) hillycum Maskey from Nepal ( Maskey 1989), S. (S) kisapense Takaoka, Sofian-Azirun & Ya’cob from Peninsular Malaysia ( Takaoka et al. 2012a) and S. (S.) lampangense Takaoka & Choochote from Thailand ( Takaoka and Choochote 2005b). However, this new species is distinguished from S. (S.) novolineatum by the ventral plate with setae ( Fig. 26 F); from the three other Indian species by the difference in the shape of the ventral plate; from S. (S.) deothangense by the female hind femur brownish-black except the basal one-fourth yellow and the apical cap black (cf., whitish yellow on little less than the basal half in S. (S.) deothangense ) and the basal protuberance of the style with several minute cone-like spines on the anterior surface ( Fig. 26 E); from S. (S.) hillycum by the female mid tibia which is whitish except its apical cap dark brown [entirely black in S. (S.) hillycum according to the figure in the original description]; and from S. (S) kisapense and S. (S.) lampangense by the male upper-eye large facets in 19 vertical columns and 20 horizontal rows (cf., in 17 or 18 vertical columns and 17–19 horizontal rows in S. (S) kisapense and S. (S.) lampangense ), and from S. (S.) lampangense by the pupal abdomen having dorsal spine-combs only on segment 8 (cf., spine-combs present on segments 7–9 in S. (S.) lampangense ).

Figures

FIGURE 25. Female of Simulium (Simulium) lacduongense sp. nov. A, third segment of maxillary palp (right side; front view); B, cibarium (front view); C, basitarsus and second tarsomere of hind leg (left side; outer view); D, sternite 8 and ovipositor valve (left half; ventral view); E, genital fork (ventral view); F & G, paraprocts and cerci (right side; F, ventral view; G, lateral view); H, spermatheca. Scale bars. 0.1 mm for C; 0.02 mm for A, B and D – H.

FIGURE 26. Male of Simulium (Simulium) lacduongense sp. nov. A, third segment of maxillary palp (right side; front view); B, basitarsus and second tarsomere of hind leg (left side; outer view); C, coxites, styles and ventral plate (ventral view); D, coxite and style (ventrolateral view); E, style (right side; medial view); F, ventral plate and median sclerite (lateral view); G, ventral plate (caudal view); H, median sclerite (ventral view); I, paramere (right side; caudal view); J, dorsal plate (ventral view); K & L, tenth abdominal segments and cerci (right side; K, lateral view; L, caudal view). Scale bars. 0.1 mm for B; 0.02 mm for A and C – L.

FIGURE 27. Pupa of Simulium (Simulium) lacduongense sp. nov. A, frontal trichomes; B, facial trichome; C – F, thoracic trichomes (C, anterodorsal; D, anterolateral; E, mediolateral; F, ventrolateral); G, gill filaments (right side; outer view); H, hairlike seta on dorsal surface of abdominal segment 1; I, hair-like seta, short seta and stout spinous seta on dorsal surface of abdominal segment 2; J, cocoon (lateral view). Scale bars. 1.0 mm for J; 0.1 mm for G; 0.02 mm for A – F, H and I; B, D, E and G.