Simulium (Gomphostilbia) breviflagellum Takaoka & Sofian-Azirun

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 : 53-57

Simulium (Gomphostilbia) breviflagellum Takaoka & Sofian-Azirun sp. nov.

( Figs. 23 A–24C)

Male. Body length 2.3 mm. Head. Somewhat wider than thorax. Upper eye dark brown, consisting of 13 or 14 vertical columns and 14 horizontal rows of large facets. Face brownish-black, grayish-white pruinose. Clypeus brownish-black, grayish-white pruinose, densely covered with yellow scale-like medium-long hairs (mostly directed upward) interspersed with several dark-brown longer hairs. Antenna ( Fig. 23 A) composed of scape, pedicel and eight flagellomeres, dark brown except scape, pedicel and base of first flagellomere whitish yellow, and rest of first flagellomere and second flagellomere dark yellow; first flagellomere elongate, 1.43 times as long as second one. Maxillary palp light to medium brown, with five segments, proportional lengths of third, fourth, and fifth segments 1.0:1.2:2.8; third segment ( Fig. 23 B) widened apically; sensory vesicle ( Fig. 23 B) elongate, 0.44 times length of third segment, and with medium-sized opening. Thorax. Scutum brownish black, shiny when illuminated at certain angles, and densely covered with brassy scale-like recumbent hairs except narrow areas along lateral margins and prescutellar area covered with yellow similar hairs. Scutellum dark brown, covered with brassy short hairs and dark-brown long upright hairs along posterior margin. Postnotum brownish-black, shiny when illuminated at certain angles, and bare. Pleural membrane bare. Katepisternum longer than deep, dark brown to brownish-black, grayish-white pruinose and shiny when illuminated at certain angles, moderately covered with fine short hairs. Legs. Foreleg: coxa whitish-yellow; trochanter dark yellow except basal half whitish-yellow; femur light brown with apical cap medium brown (though extreme tip yellowish); tibia white or yellowish-white except basal one-fourth (though basal tip paler) and apical one-fourth light brown, with brilliant white sheen widely on outer surface when illuminated at certain angles; tarsus black, with moderate dorsal hair crest; basitarsus moderately dilated, 6.6 times as long as its greatest width. Midleg: coxa medium brown except posterolateral surface brownish-black; trochanter dark yellow or light brown; femur medium brown, with apical cap dark brown (though extreme tip yellowish); tibia yellowish-white on basal one-third or little more, and medium to dark brown on rest, with brilliant white sheen on posterior surface of basal one-third or little more when illuminated at certain angles; tarsus medium to dark brown except basal half or little more of basitarsus yellowish-white. Hind leg: coxa medium brown; trochanter yellowish-white; femur medium brown, with base yellowish-white and apical cap dark brown (though extreme tip yellowish-white); tibia ( Fig. 23 C) white or yellowish-white on basal half and medium to dark brown on rest; tibia with brilliant white sheen on outer and posterior surfaces of basal half; tarsus medium to dark brown except basal two-thirds or little more of basitarsus (though basal tip light brown) and basal half of second tarsomere yellowish white; basitarsus ( Fig. 23 D) narrow, nearly parallel-sided, 6.89 times as long as wide, and 0.57 and 0.46 times as wide as greatest widths of tibia and femur, respectively; calcipala ( Fig. 23 D) slightly longer than width at base, and 0.58 times as wide as greatest width of basitarsus; pedisulcus ( Fig. 23 D) well developed. Wing. Length 1.9 mm. Costa with dark spinules and hairs except basal patch of hairs whitish yellow. Subcosta bare. Hair tuft on base of radial vein yellow. Basal portion of radius fully haired; R1 with dark spinules and hairs; R2 with hairs only. Basal cell absent. Halter . Grayish white except basal portion darkened. Abdomen. Basal scale dark brown, with fringe of light to medium brown hairs. Dorsal surface of abdomen medium brown to black (except tergal plate of each side of segment 2 yellowish), covered with dark-brown short to long hairs; segments 2 and 5–8 each with pair of shiny dorsolateral or lateral patches. Genitalia. Coxite in ventral view ( Fig. 23 E) nearly rectangular, 1.54 times as long as its greatest width. Style in ventral view ( Fig. 23 E) bent inward, slightly tapered from base toward middle, then nearly parallel-sided toward apex, and with apical spine (right style with additional spine near apex on ventral surface); style in medial view ( Fig. 23 F) shorter than coxite (0.88 times length of coxite), gently bent inward, slightly tapered toward apex, with round apex; style in ventrolateral view ( Fig. 23 G) nearly parallel-sided form base to basal one-fourth, abruptly narrowed, then parallel-sided up to apical one-fourth, and gradually tapered toward apex, with round apex. Ventral plate in ventral view ( Fig. 23 E) with body transverse, 0.5 times as long as wide, slightly rounded laterally, with anterior margin slightly produced anteromedially, and posteroventral margin somewhat concave (though posterodorsal margin slightly convex medially), densely covered with microsetae on ventral surface; basal arms of moderate length, directed forward; ventral plate in lateral view ( Fig. 23 H) moderately produced ventrally; ventral plate in caudal view ( Fig. 23 I) produced ventrally (width:height ratio 1.0:0.6), with round apex, densely covered with microsetae on central portion of posterior surface. Median sclerite ( Fig. 23 H, J) thin, plate-like, wide, with sclerotized portion tapered toward apex. Paramere ( Fig. 23 K) of moderate size, with three long hooks. Aedeagal membrane ( Fig. 23 K) moderately setose; dorsal plate not well defined. Ventral surface of abdominal segment 10 ( Fig. 23 L, M) weakly sclerotized widely, without distinct hairs near posterior margin. Cercus ( Fig. 23 L, M) small, rounded, with 8–11 hairs.

Pupa. Body length 2.4 mm. Head. Integument yellow, moderately covered with small round tubercles; antennal sheath without protuberances; frons with three pairs of unbranched long trichomes with coiled apices; face with pair of unbranched long trichomes with coiled or uncoiled apices; three frontal trichomes on each side arising close together, subequal in length to one another and slightly longer than facial one. Thorax. Integument yellow, moderately covered with round tubercles except dorsomedial areas sparsely covered with tubercles, with three long anterodorsal trichomes with coiled or uncoiled apices, two long anterolateral trichomes (one with coiled apex, one with uncoiled apex), one medium-long mediolateral trichome with uncoiled apex, and three ventrolateral trichomes with uncoiled apices (one medium-long, two short) on each side; all trichomes unbranched. Gill ( Fig. 24 A) composed of eight slender thread-like filaments, arranged as [(1+2) +(1+2)]+2 filaments from dorsal to ventral, with medium-long common basal stalk having somewhat swollen unpigmented basal fenestra ventrally (partially broken) at base; common basal stalk 0.78 times length of interspiracular trunk; dorsal and middle triplets sharing short stalk; dorsal and middle triplets each composed of one individual filament and two paired filaments with short primary stalk and long secondary stalk, which is about three times as long as primary stalk; ventral paired filaments with medium-long stalk nearly as long as common basal stalk; stalk of ventral pair as thick as primary stalk of middle triplet, 1.23 times as thick as primary stalk of dorsal triplet, and 0.89 times as thick as common stalk of middle and dorsal triplets; primary stalk of dorsal triplet lying against that of lower pair at angle of 90 degrees when viewed laterally; all filaments light brown, gradually tapered toward apex; lengths of all filaments are not measurable due to loss of apical portions of all filaments; two filaments of ventral pair subequal in length and thickness to each other, and somewhat thicker than six other filaments when compared basally; cuticle of all filaments with moderately-defined annular ridges and furrows though becoming less marked apically, densely covered with minute tubercles. Abdomen. Dorsally, all segments unpigmented and without tubercles; segment 1 with one unbranched slender medium-long hair-like seta on each side; segment 2 with one unbranched slender medium-long hair-like seta and five short somewhat spinous setae submedially on each side; segments 3 and 4 each with four hooked spines and one short somewhat spinous seta on each side; segment 5 lacking spinecombs; segments 6–9 each with spine-combs in transverse row (though those on segment 9 much smaller than those on segment 8) and comb-like groups of minute spines on each side; segment 9 with pair of wide flat terminal hooks, of which outer margin is 3.6 times as long as inner margin and serrated ( Fig. 24 B). Ventrally, segment 4 with one unbranched hook and few unbranched slender short setae on each side; segment 5 with pair of bifid hooks submedially and few short unbranched slender setae on each side; segments 6 and 7 each with pair of bifid inner and unbranched outer hooks somewhat spaced from each other and few short unbranched slender setae on each side; segments 4–8 each with comb-like groups of minute spines. Each side of segment 9 with three grapnel-shaped hooklets. Cocoon ( Fig. 24 C). Wall-pocket-shaped, moderately woven, widely extended ventrolaterally; anterodorsal margin thickly woven, with short anterodorsal projection; posterior one-half with floor roughly woven; individual threads visible; 3.0 mm long by 2.2 mm wide.

Female and mature larva. Unknown.

Type material. HOLOTYPE: Male, 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.

Biological notes. The pupa of this new species was collected from a grass leaf trailing in the water. Associated species were S. (G.) longlanhense sp. nov., S. (G.) thituyenae sp. nov. and S. (S.) xuandei sp. nov.

Etymology. The species name breviflagellum refers to the shortened flagellum of this new species due to lack of one of nine flagellomeres.

Remarks. Simulium (G.) breviflagellum sp. nov. is assigned to the S. varicorne species-group of the subgenus Gomphostilbia , redefined by Takaoka (2012), since it has eight flagellomeres on its adult antenna ( Fig. 23 A), and is, within it, further placed in the burtoni subgroup because of its male ventral plate moderately produced ventrally ( Fig. 23 I), as defined by Takaoka (2012).

This new species is similar to all three known species of this subgroup in the shape of the male genitalia but is distinguished from them by the following characters (those of known species in parentheses): from S. (G.) shogakii (Rubtsov) from Japan, Korea and northern China ( Rubtsov 1959 –1964) by the long secondary stalks of the dorsal and middle triplets of gill filaments, which are twice the length of their primary stalks ( Fig. 24 A) (secondary stalks are short, nearly as long as the primary stalks), and serrated terminal hooks ( Fig. 24 B) (simple, cone-shaped terminal hooks), and cocoon with an anterodorsal projection ( Fig. 24 C) (cocoon without such a projection); from S. (G.) burtoni Takaoka & Davies from Peninsular Malaysia and Thailand ( Takaoka and Davies 1995) by the cocoon with an anterodorsal projection (cocoon without such a projection); and from S. (G.) synanceium Chen & Cao from northern China ( Chen and Cao 1983) by the elongate male sensory vesicle ( Fig. 23 B) (small, globular sensory vesicle), hind tibia with the apical half darkened (hind tibia darkened on the basal one-fourth and the apical onethird), and long secondary stalks of the dorsal and middle triplets of gill filaments, which are twice the length of their primary stalks (secondary stalks are short, nearly as long as the primary stalks).

This is the first record of the S. varicorne species-group from Vietnam.

Figures

FIGURE 23. Male of Simulium (Gomphostilbia) breviflagellum sp. nov. A, antenna (right side; dorsal view); B, third segment of left maxillary palp with sensory vesicle (front view); C, tibia of hind leg (left side; outer view); D, basitarsus and second tarsomere of hind leg showing calcipala and pedisulcus (left side; outer view); E, coxites, styles and ventral plate (ventral view); F & G, styles (right side; F, medial view; G, ventrolateral 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 & M, tenth abdominal segments and cerci (right side; L, lateral view; M, caudal view). Scale bars. 0.1 mm for C and D; 0.05 mm for A; 0.02 mm for B and E – M.

FIGURE 24. Pupa of Simulium (Gomphostilbia) breviflagellum sp. nov. A, gill filaments (right side; outer view); B, terminal hooks (caudal view); C, cocoon (dorsal view). Scale bars. 1.0 mm for C; 0.1 mm for A; 0.02 mm for B.