Simulium (Simulium) xuandei Takaoka & Pham

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 : 86-92

Simulium (Simulium) xuandei Takaoka & Pham sp. nov.

( Figs. 39 A–41L)

Female. Body length 1.8–2.0 mm. Head. Slightly narrower than thorax. Frons black, shiny with bluish reflection when illuminated at certain angles, with several dark stout hairs along lateral margins; frontal ratio 1.45– 1.46:1.00:1.16–1.21; frons:head ratio 1.00:3.03–3.35. Fronto-ocular area well developed, short, directed laterally, and rounded apically. Clypeus black, shiny with bluish reflection when illuminated at certain angles, moderately covered with dark-brown medium-long hairs though mediolongitudinal portion widely bare. Labrum 0.53–0.56 times length of clypeus. Antenna composed of scape, pedicel and nine flagellomeres; antenna dark brown, except scape, pedicel and base of first flagellomere yellow. Maxillary palp with five segments, medium brown except segments 1 and 2 ochreous or light brown, and segment 3 dark brown; proportional lengths of third, fourth, and fifth segments 1.00:1.17–1.25:2.53–2.69; third segment ( Fig. 39 A) of moderate size; sensory vesicle medium-sized (0.33–0.37 times length of third segment), ellipsoidal, having medium-sized opening. Maxillary lacinia with 16 or 17 inner and 19–21 outer teeth. Mandible with 26–29 inner and 11–13 outer teeth. Cibarium ( Fig. 39 B) with 47–54 minute processes near posterodorsal margin. Thorax. Scutum black, shiny with bluish reflection when illuminated at certain angles, moderately covered with dark short fine hairs interspersed with several dark-brown long upright hairs on prescutellar area. Scutellum dark brown, shiny when illuminated at certain angles, covered with darkbrown upright long hairs. Postnotum brownish-black, shiny when illuminated at certain angles, and bare. Pleural membrane bare. Katepisternum longer than deep, brownish-black, shiny when illuminated at certain angles, and bare. Legs. Foreleg: coxa whitish yellow; trochanter light brown; femur light to medium brown with apical cap dark brown; tibia medium brown except apical cap dark brown, with median outer surface widely white and with bright white sheen when illuminated at certain angles; tarsus black, with moderate dorsal hair crest; basitarsus greatly dilated, 4.92–5.00 times as long as its greatest width. Midleg: coxa brownish-black; trochanter medium brown; femur medium brown except apical cap dark brown; tibia medium brown except base yellowish white and apical cap dark brown, and with whitish sheen widely on posterior surface when illuminated at certain angles; tarsus medium brown except basal four-fifths of basitarsus and base of second tarsomere yellowish-white. Hind leg: coxa medium brown; trochanter yellowish-white; femur medium brown except extreme base yellowish-white; tibia medium to dark brown except base yellowish-white and with whitish sheen widely on posterior surface when illuminated at certain angles; tarsus medium brown except basal two-thirds of basitarsus and basal half of second tarsomere yellowish-white; basitarsus ( Fig. 39 C) nearly parallel-sided, 5.66–6.15 times as long as wide, and 0.72 and 0.60–0.63 times as wide as greatest widths of hind tibia and femur, respectively; calcipala ( Fig. 39 C) moderately developed, nearly as long as wide, and 0.42 times as wide as greatest width of basitarsus; pedisulcus ( Fig. 39 C) well developed; claw ( Fig. 39 D) simple, without tooth. Wing. Length 1.7 mm. Costa with dark spinules and hairs; subcosta haired except apical half to one-fifth bare; basal section of radial vein bare; R1 with dark brown spinules and hairs; R2 with dark-brown hairs; hair tuft on base of radial vein dark brown; basal cell absent. Halter . White except basal portion darkened. Abdomen. Basal scale dark brown, with fringe of yellow hairs. Dorsal surface of abdomen medium-brown to brownish-black, with dark short hairs; tergite 2 shiny and silvery iridescent when illuminated at certain angles and tergites 6–9 shiny and iridescent when illuminated at certain angles. Ventral surface of segment 7 with pair of weakly sclerotized submedian sternal plates. Genitalia. Sternite 8 ( Fig. 39 E) well sclerotized and bare medially, covered with six to eight long and medium-long stout hairs and few short fine hairs on each side. Ovipositor valves ( Fig. 39 E) nearly triangular, rounded posteromedially, membranous except inner margins weakly sclerotized, densely covered with microsetae together with three to five short fine hairs; inner margin nearly straight or slightly concave medially. Genital fork ( Fig. 39 F) of inverted-Y form; stem slender and well sclerotized, with rounded apex; arms of moderate width, each with strongly-sclerotized projection directed forward from lateral ridge. Paraproct in ventral view ( Fig. 39 G) pointed posteromedially, moderately concave anterolaterally, and with strongly sclerotized anteromedial surface; paraproct in lateral view ( Fig. 39 H) somewhat produced ventrally and slightly posteriorly, 0.74 times as long as wide, covered with 11–22 medium-long stout hairs and numerous microsetae on lateral and ventral surfaces. Cercus in lateral view ( Fig. 39 H) short, rounded posteriorly, 0.47 times as long as its greatest width, and covered with medium-long and short stout hairs. Spermatheca ( Fig. 39 I) ovoidal, 1.12–1.17 times as long as wide, well sclerotized except duct and narrow area of junction with duct unsclerotized, without discernible reticulate surface patterns; minute internal setae present; accessory ducts subequal in thickness to each other and slightly thicker than main duct.

Male. Body length 2.0 mm. Head. Slightly wider than thorax. Upper eye medium brown, consisting of large facets in 18 vertical columns and in 19 horizontal rows. Clypeus black, thickly white pruinose, silvery shiny when illuminated at certain angles, covered with dark-brown hairs along and near lateral margins (most of central portion bare). Antenna composed of scape, pedicel and nine flagellomeres, brownish-black except scape and pedicel light to medium brown; first flagellomere elongate, 1.7–1.9 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 1.0:1.3:2.7; third segment ( Fig. 40 A, B) widened apically; sensory vesicle ( Fig. 40 A, B) small, 0.09–0.21 times as long as third segment, ellipsoidal, and with small opening. Thorax. Scutum black, with white pruinose pattern, i.e., anterior pair of triangular spots (not sharply pointed posteriorly) on shoulders extending posteriorly along lateral margins but not connected to large transverse spot entirely covering prescutellar area; these pruinose areas silvery or bluish iridescent when illuminated at certain angles; scutum uniformly and densely covered with brassy recumbent short hairs interspersed with dark-brown long upright hairs on prescutellar area. Scutellum brownish-black, with several dark-brown long upright hairs. Postnotum brownish-black, white pruinose when illuminated at certain angles and bare. Pleural membrane bare. Katepisternum longer than deep, brownish-black, thinly white pruinose and shiny when illuminated at certain angles, and bare. Legs. Color as in female except hind trochanter dark yellow, and hind basitarsus yellowish-white on basal half. Fore basitarsus greatly dilated, 5.1 times as long as its greatest width. Hind basitarsus ( Fig. 40 C) much enlarged, gradually widened from base to apical two-fifths, then slightly narrowed toward apex, 3.90–3.94 times as long as its greatest width, and 0.77–0.81 and 0.86–0.91 times as wide as greatest widths of hind tibia and femur, respectively; calcipala ( Fig. 40 C) small, nearly as long as wide, 0.25 times as wide as greatest width of basitarsus; pedisulcus ( Fig. 40 C) well developed. Wing. Length 1.6–1.7 mm. Other features as in female except subcosta bare. Halter . White except basal portion darkened. Abdomen. Basal scale brownishblack, with fringe of pale (though basally dark) long hairs. Dorsal surface of abdomen brownish-black to black, 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. 40 D) nearly quadrate, covered with stout hairs near posterior margin. Style in ventral view ( Fig. 40 D) elongate, gradually tapered from base to middle, then nearly parallel-sided, with apical spine; style in ventrolateral view ( Fig. 40 E) elongate, 3.1 times as long as its greatest width at basal two-fifths, slightly widened from base to basal two-fifths, much tapered toward middle, then nearly parallel-sided; style in medial view ( Fig. 40 F) 1.6 times as long as coxite, somewhat produced dorsally near base and with several small cone-like spines on dorsal surface. Ventral plate in ventral view ( Fig. 40 D) well sclerotized, with body subquadrate (though rounded on each posterolateral corner), 0.7 times as long as wide, posterior margin somewhat convex, and with round projection directed ventrally which is covered with many minute setae; arms directed forward and somewhat divergent from each other; ventral plate in lateral view ( Fig. 40 G) with posterior margin serrated along basal half; ventral plate in caudal view ( Fig. 40 H) rounded ventrally, with lateral margins serrated along basal half, with numerous setae on posterior surface except both areas of dorsolateral corners bare. Median sclerite ( Fig. 40 G, I) plate-like, gradually widened from base toward apex, with round apex, brown basally, but not sclerotized apically. Paramere ( Fig. 40 J) with several distinct hooks and several smaller ones. Aedeagal membrane moderately covered with minute setae, and with moderately sclerotized dorsal plate in form of horizontal bar ( Fig. 40 K). Abdominal segment 10 ( Fig. 40 L, M) with four to seven hairs on lateral surface on each side. Cercus ( Fig. 40 L, M) small, rounded, with six to eight distinct hairs.

Pupa. Body length 2.0– 2.3 mm. Head. Integument including antennal sheaths yellow; frons moderately covered with tubercles, some of which having minute secondary projections ( Fig. 41 A), and with two pairs of unbranched short trichomes ( Fig. 41 B); face with pair of unbranched short trichomes ( Fig. 41 C). Thorax. Integument yellow, moderately covered with tubercles, of which those on anterodorsal surface have minute secondary projections (similar to Fig. 41 A); thorax on each side with two medium-long anterodorsal trichomes ( Fig. 41 D), two medium-long anterolateral trichomes (one sometimes slightly thinner and shorter than other) ( Fig. 41 E), one short mediolateral trichome ( Fig. 41 F), and three short ventrolateral trichomes (one slightly shorter and thinner than two others) ( Fig. 41 G); all trichomes unbranched. Gill ( Fig. 41 H) with six slender thread-like filaments in three pairs (one dorsal, one middle and one ventral) arising from short common basal stalk; basal fenestra small; all pairs short-stalked, and stalks of dorsal and ventral pairs lying at angle of 90 or little more degrees when viewed laterally; all filaments subequal in length (1.4–1.7 mm long) and thickness to one another except ventral pair of filaments slightly shorter and thinner than others; all filaments medium-brown, tapered toward apex, with distinct annular ridges and furrows forming definite reticulate surface patterns (except stalks and basal portions of filaments smooth), and densely covered with minute tubercles. Abdomen. Dorsally, all segments unpigmented except segment 1, basal half of segment 2, and segment 9 light yellowish; segment 1 with one unbranched short seta on each side; segment 2 with one unbranched short seta and five spinous short setae on each side; segments 3 and 4 each with four distinct hooked spines and one unbranched spinous short seta on each side; segments 5 and 6 lacking spine-combs; segments 7–9 each with distinct spine-combs in transverse row and comblike groups of minute spines on each side; segment 9 with small terminal hooks ( Fig. 41 I). Ventrally, segments 4–9 unpigmented except segment 9 somewhat yellowish, each with comb-like groups of minute spines; segment 4 with one unbranched or bifid stout hooklet and few 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. Wall-pocket-shaped, moderately woven, thin, ochreous, and not extended ventrolaterally; individual threads visible; 2.3–2.8 mm long by 1.0– 1.2 mm wide.

Mature larva. Body length 3.5–4.0 mm. Thoracic segment 1 and abdominal segments 1–4 each encircled by broad dark-brown transverse band and abdominal segments 5–9 dark brown on dorsal and dorsolateral surfaces; thoracic segments 2 and 3 dark brown on ventral surface and abdominal segments 4–6 with dark mediolongitudial band on ventral surface. Cephalic apotome yellow; head spots almost indistinct or faintly positive though anterior spot of mediolateral spots negative. Lateral surface of head capsule yellow except eye-spot region whitish and areas posterior to eye-spot region somewhat darkened. Ventral surface of head capsule ( Fig. 41 L) yellowish; long spot on each side of postgenal cleft indistinct. Antenna composed of three segments and apical sensillum, slightly longer than stem of labral fan; length ratio of three segments (from base to tip) 1.0:1.3:0.9. Labral fan with 33–36 main rays. Mandible ( Fig. 41 J) with serrations composed of two teeth (one medium-sized, one small); main tooth at right angle against mandible on apical side; supernumerary serrations absent; comb-teeth decreasing in length from first to third. Hypostoma ( Fig. 41 K) with nine anterior teeth, of which corner teeth most prominent, slightly longer than median tooth, and intermediate teeth shortest; lateral margins serrate apically; four hypostomal bristles per side nearly parallel to lateral margin on each side. Postgenal cleft ( Fig. 41 L) arrow-head shaped, long, 5.9 times length of postgenal bridge; sheath of subesophageal ganglion not pigmented. Cervical sclerites on each side composed of one medium brown elongate piece and one light brown elliptical piece, not fused to occiput. Histoblast of pharate pupal gill with six short filaments. Thoracic and abdominal cuticle almost bare except last segment of abdomen moderately covered with short colorless setae on each side of anal sclerite. Rectal scales present. Rectal organ compound, each lobe with seven to nine finger-like secondary lobules. Anal sclerite Xshaped, with short broad anterior arms 0.6 times as long as posterior ones; one to three sensilla on junction; five or six sensilla posterior to posterior arms. Last abdominal segment somewhat swollen laterally but lacking ventral papillae. Posterior circlet with 66–72 rows of hooklets with up to 12 hooklets per row.

Type material. HOLOTYPE: Female, reared from a pupa collected from a small stream (width 4–6 m, water temperature 18.0˚C, exposed to the sun, altitude 1,452 m, 12˚10’56.408” N/108˚40’48.152” E), moderately flowing in open land, Long Lanh, Lac Duong District, Lam Dong Province, southern Vietnam, 24-IV-2014, by H. Takaoka, M. Sofian-Azirun, Z. Ya’cob, C.D. Chen & K.W. Lau. PARATYPES: 11 females and five males and two mature larvae, same data as those of the holotype; one female, three males and two pupae collected from a small stream (width 1–2 m, water temperature 16.0˚C, exposed to the sun, altitude 1,492 m) (12˚07’59.430” N/ 108˚35’42.001” E) slowly flowing in open land, 45 km from Dalat, Da Chais, Lac Duong, Lam Dong Province, southern Vietnam, 24-IV-2014, by H. Takaoka, M. Sofian-Azirun, Z. Ya’cob, C.D. Chen & K.W. Lau.

Biological notes. The pupae and larvae of this new species were collected from leaves of trailing grasses and fallen tree leaves in small streams. Associated species were S. (G.) breviflagellum sp. nov., S. (G.) hongthaii , S. (G.) longlanhense sp. nov., S. (G.) thituyenae sp. nov. and S. (S.) chamlongi .

Etymology. The species name xuandei is in honor of Mr. Xuan De Pham, father of Dr. Xuan Da Pham, for his longstanding support and encouragement.

Remarks. Simulium (S.) xuandei sp. nov. is assigned to the S. tuberosum species-group of the subgenus Simulium , redefined by Takaoka and Davies (1996), based on the male genitalia, of which the ventral plate is quadrate or subquadrate when viewed ventrally, having a round projection directed ventrally with serrated posterolateral margins ( Fig. 40 D), and the style has several cone-like spines subbasally on the dorsal surface ( Fig. 40 F).

This new species is similar to cytoform ‘L’ of the S. (S.) tani (complex) from Taiwan ( Huang and Adler 2011; Adler et al. 2013), which was previously recognized as S. (S.) suzukii Rubtsov by Takaoka (1979), in having a similar number of male upper-eye facets (i.e., 18 vertical columns and 19 horizontal rows) and a similar arrangement of six pupal gill filaments (divergent basally at about 90 degrees when viewed laterally). However, the pupa of this new species is distinguished from that of cytoform ‘L’ of the S. (S.) tani (complex) by the tubercles having secondary projections ( Fig. 41 A) on the frons and anterodorsal surface of the thorax. This new species is also similar in the arrangement of the pupal gill filaments to S. (S.) jasmoni Takaoka, Sofian-Azirun & Belabut from Peninsular Malaysia ( Takaoka et al. 2012b) and S. (S.) suzukii from Japan, but is easily distinguished from these two known species in the male by the number of upper-eye facets in 18 vertical columns and 19 horizontal rows (cf., 16 vertical columns and 17 horizontal rows in S. (S.) jasmoni , and 20 vertical columns and 21 horizontal rows in S. (S.) suzukii ), and in the pupa by the tubercles having secondary projections ( Fig. 41 A) on the frons and anterodorsal surface of the thorax (cf., tubercles smooth without such secondary projections in S. (S.) jasmoni and S. (S.) suzukii ). In addition, this new species is distinguished in the female from S. (S.) jasmoni by the mediumsized sensory vesicle (cf., the sensory vesicle is elongate, 0.6 times the length of the third maxillary palpal segment in S. (S.) jasmoni ) and in the male from S. (S.) suzukii by the whitish-yellow fore coxae (cf., the fore coxae are light brown in S. (S.) suzukii ).

Figures

FIGURE 39. Female of Simulium (Simulium) xuandei 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, claw; E, sternite 8 and ovipositor valve (right half; ventral view); F, genital fork (ventral view); G & H, paraprocts and cerci (right side; G, ventral view; H, lateral view); I, spermatheca. Scale bars. 0.05 mm for C; 0.02 mm for A, B and E – I; 0.01 mm for D.

FIGURE 40. Male of Simulium (Simulium) xuandei sp. nov. A & B, third segments of maxillary palps with sensory vesicles of different size (left side; front view); C, basitarsus and second tarsomere of hind leg (left side; outer view); D, coxites, styles and ventral plate (ventral view); E & F, styles (right side; E, ventrolateral view; F, medial view); G, ventral plate and median sclerite (lateral view); H, ventral plate (caudal view); I, median sclerite (ventral view); J, paramere (right side; caudal view); K, dorsal plate (ventral view); L & M, tenth abdominal segments and cerci (right side; L, lateral view; M, caudal view). Scale bars. 0.1 mm for C; 0.02 mm for A, B and D – M.

FIGURE 41. Pupa and mature larva of Simulium (Simulium) xuandei sp. nov. A – I, pupa; J – L, larva. A, tubercles with minute secondary projections on frons; B, frontal trichomes; C, facial trichome; D – G, thoracic trichomes (D, anterodorsal; E, anterolateral; F, mediolateral; G, ventrolateral); H, gill filaments (right side; outer view); I, terminal hooks (caudal view); J, mandible; K, hypostoma; L, head capsule with postgenal cleft (ventral view). Scale bars. 0.1 mm for H; 0.05 mm for L; 0.02 mm for A – G and I – K.