Simulium (Gomphostilbia) thituyenae 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 : 24-28

Simulium (Gomphostilbia) thituyenae Takaoka & Pham sp. nov.

( Figs. 9 A– 10I)

Female. Body length 2.2 mm. Head. Slightly narrower than width of thorax. Frons dark brown, densely covered with yellowish-white scale-like recumbent short hairs interspersed with few dark longer hairs near vertex; frontal ratio 1.72:1.00:2.34; frons:head ratio 1.00:4.31. Fronto-ocular area well developed, narrow, directed dorsolaterally. Clypeus dark brown, densely covered with yellowish-white hairs interspersed with several dark longer hairs near ventral margin. Labrum 0.55 times length of clypeus. Antenna composed of scape, pedicel and nine flagellomeres, dark brown except scape, pedicel, and base of first flagellomere yellow; first flagellomere 1.8 times length of second one. Maxillary palp composed of five segments, light to medium brown except segments 1 and 2 dark yellow, proportional lengths of third, fourth, and fifth segments 1.00:0.95:2.05; third segment ( Fig. 9 A) widened; sensory vesicle ( Fig. 9 A) large, elongate (0.63–0.64 times length of third segment), with medium-sized opening. Maxillary lacinia with 13 inner and 17 or 18 outer teeth. Mandible with 26 inner teeth and eight outer teeth at some distance from apex. Cibarium ( Fig. 9 B) medially forming sclerotized plate folded forward from posterior margin, with moderately sclerotized mediolongitudinal ridge. Thorax. Scutum dark brown to brownish-black except anterolateral calli ochreous, thinly pruinose and shiny when illuminated at certain angles, densely covered with whitish-yellow to yellow scale-like recumbent hairs. Scutellum ochreous, covered with yellow short hairs and dark-brown long upright hairs along posterior margin. Postnotum dark brown, whitish-gray pruinose and shiny when illuminated at certain angles, and bare. Pleural membrane bare. Katepisternum longer than deep, medium to dark brown, shiny when illuminated at certain angles, moderately covered with fine short hairs. Legs. Foreleg: coxa whitish-yellow; trochanter light brown though posterior surface whitish-yellow; femur light brown with apical cap medium brown (though extreme tip yellowish); tibia white except apical one-fourth brownish-black, covered with white fine hairs on basal four-fifths; tarsus brownish-black, with moderate dorsal hair crest; basitarsus moderately dilated, 5.9 times as long as its greatest width. Midleg: coxa dark brown; trochanter yellow to dark yellow with base whitish-yellow; femur dark yellow to light brown with basal one-third of outer surface yellowish (and basal half of inner surface yellow) and apical cap medium brown (though extreme tip yellowish); tibia light brown except basal two-fifths whitish-yellow and apical cap dark brown (and apical three-fifths of posterior surface dark brown), covered with whitish and yellowish fine hairs on posterior and inner surfaces of little more than basal half; tarsus dark brown though base of basitarsus medium brown. Hind leg: coxa light brown; trochanter whitish-yellow; femur light brown with base whitish-yellow and apical cap medium brown (though extreme tip yellowish); tibia ( Fig. 9 C) white or yellowish-white on little more than basal half and light brown on rest though apical cap brownish-black, covered with whitish fine hairs on outer and posterior surfaces of little more than basal three-fourths; tarsus brownish-black except basal two-thirds of basitarsus (though base light brown) and basal half of second tarsomere whitish; basitarsus ( Fig. 9 D) narrow, nearly parallel-sided though slightly narrowed apically, 6.29 times as long as wide, and 0.64 and 0.54 times as wide as greatest widths of tibia and femur, respectively; calcipala ( Fig. 9 D) nearly as long as width at base, and 0.56 times as wide as greatest width of basitarsus; pedisulcus ( Fig. 9 D) well developed; claw ( Fig. 9 E) with large basal tooth 0.5 times length of claw. Wing. Length 2.0 mm. Costa with dark spinules and hairs except basal patch of hairs yellow. Subcosta with dark hairs except near apex 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 . White except basal portion darkened. Abdomen. Basal scale light ochreous, with fringe of whitish-yellow hairs. Dorsal surface of abdomen light to dark brown except basal half of segment 2 yellowish-white, moderately covered with dark short to long hairs (except segment 2 with yellow fine hairs); tergites of segments 2 and 6–9 shiny when illuminated at certain angles. Ventral surface of segments 2 and 3 yellowish-white, those of other segments light to medium brown; sternal plate on segment 7 undeveloped. Genitalia. Sternite 8 ( Fig. 9 F) bare medially, with 16 or 17 medium-long to long hairs together with few slender short hairs on each side. Ovipositor valves ( Fig. 9 F) triangular (though posteromedial corners rounded), thin, membranous, moderately covered with microsetae interspersed with three or four short hairs; inner margins nearly straight or slightly sinuous, somewhat sclerotized, and moderately separated from each other. Genital fork ( Fig. 9 G) of usual inverted-Y form, with slender stem; arms of moderate width, moderately folded medially, without lobe directed posteromedially. Paraproct in ventral view ( Fig. 9 H) somewhat concave anterolaterally, with four or five sensilla on anteromedial surface; paraproct in lateral view ( Fig. 9 I) slightly produced ventrally beyond ventral tip of cercus, 0.6 times as long as wide, with 20–22 medium-long to long hairs on ventral and lateral surfaces. Cercus in lateral view ( Fig. 9 I) short, rounded posteriorly, 0.43 times as long as wide. Spermatheca ( Fig. 9 J) ellipsoidal, 1.61 times as long as its greatest width, well sclerotized except duct and small area near juncture with duct unsclerotized, and with many fissures on outer surface; internal setae absent; both accessory ducts slender, subequal in diameter to major one.

Pupa. Body length 2.5 mm. Head. Integument yellow, moderately covered with small round tubercles except ventral surface of face almost bare; antennal sheath without protuberances; frons with three pairs of unbranched long trichomes with coiled or uncoiled apices ( Fig. 10 A); face with pair of unbranched long trichomes with coiled apices ( Fig. 10 B); 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, with three long anterodorsal trichomes with coiled apices ( Fig. 10 C), two long anterolateral trichomes (one with coiled apex, one uncoiled apex) ( Fig. 10 D), one medium-long mediolateral trichome with uncoiled apex ( Fig. 10 E), and three short ventrolateral trichomes with uncoiled apices (one longer than other two) ( Fig. 10 F) on each side; all trichomes unbranched. Gill ( Fig. 10 G) composed of eight slender thread-like filaments, arranged as (3+3)+2 or [3+(1+2)]+2 filaments from dorsal to ventral, with medium-long common basal stalk having somewhat swollen basal fenestra ventrally (partially broken) at base; common basal stalk 0.76 times length of interspiracular trunk; dorsal and middle triplets sharing short stalk; dorsal triplet composed of three filaments arising at same level, and with short primary stalk; middle triplet composed of three filaments arising at same level in right gill but composed of one individual filament and two paired filaments with short primary and second stalks in left gill; ventral paired filaments with medium-long stalk 1.05 times length of common basal stalk, and 0.8 times as thick as common basal stalk, nearly as thick as common stalk of dorsal and middle triplets, 1.3 times as thick as stalk of middle triplet, and 1.5 times as thick as stalk of dorsal triplet; stalk of dorsal triplet lying against that of lower pair at angle of 60 degrees when viewed laterally; all filaments dark brown, gradually tapered toward apex; three filaments of dorsal triplet 1.5–1.7 mm long, three filaments of middle triplet 1.8–2.0 mm long, and two filaments of ventral pair longest (probably little longer than 2.5 mm, though exact length unmeasurable due to loss of tips); two filaments of ventral pair subequal in thickness to each other, and somewhat thicker than six other filaments when compared basally; cuticle of all filaments with well-defined annular ridges and furrows though becoming less marked apically, densely covered with minute tubercles. Abdomen. Dorsally, all segments faintly yellowish and without tubercles; segment 1 with one unbranched slender short hair-like seta on each side; segment 2 with one unbranched slender short hair-like seta and five short spinous setae submedially on each side; segments 3 and 4 each with four hooked spines and one short spinous seta on each side; segment 5 lacking spine-combs; segments 6–9 each with spine-combs in transverse row and comb-like groups of minute spines on each side; segment 9 with pair of flat small terminal hooks ( Fig. 10 H). Ventrally, segment 4 with one unbranched hooklet and few unbranched slender short setae on each side; segment 5 with pair of unbranched inner and bifid outer hooks on left side, bifid inner and unbranched outer hooks on right side, and few short unbranched slender setae on each side; segment 6 with pair of bifid inner and unbranched outer hooklets on left side, and segment 7 with pair of unbranched inner and bifid outer hooklets on left side, though both segments each with pair of bifid inner and outer hooks on right side, both segments each with 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. 10 I). Wall-pocket-shaped, moderately woven with dark threads, leaving numerous small open spaces ventrolaterally, widely extended ventrolaterally; anterior margin thickly woven, with dorsomedial portion slightly produced anteriorly forming short bulge when viewed dorsally; posterior three-fifths with floor roughly woven; individual threads visible; 3.4 mm long by 2.9 mm wide.

Male and mature larva. Unknown.

Type material. HOLOTYPE. Female, reared from 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.

Etymology. The species name thituyenae is in honor of the late Thi Tuyen Tran, mother of Dr. Xuan Da Pham, for her longstanding support and encouragement.

Biological notes. The pupa of this new species was collected from a dead tree leaf in the water of a stream. Associated species were S. (G.) breviflagellum sp. nov., S. (G.) hongthaii , S. (G.) longlanhense sp. nov. and S. (S.) xuandei sp. nov.

Remarks. Simulium (G.) thituyenae sp. nov. is temporarily placed in the S. asakoae species-group since it resembles S. (G.) lurauense Takaoka, Sofian-Azirun & Hashim , and S. (G.) sofiani , both described from Peninsular Malaysia and placed in this species-group ( Takaoka et al. 2011a, b), in many characters including the yellow hair tuft of the base of the female radial vein, elongate female sensory vesicle ( Fig. 9 A), and small pupal terminal hooks ( Fig. 10 H).

This new species is distinguished from S. (G.) lurauense by the relative length of the female sensory vesicle against the third maxillary palpal segment (0.63–0.64 in this new species versus 0.50–0.54 in S. (G.) lurauense ), and color of the female mid basitarsus (nearly dark brown in this new species versus dark brown except the basal one-third yellow in S. (G.) lurauense ), and from S. (G.) sofiani by the relative length of the common basal stalk of the pupal gill against the interspiracular trunk (0.77 in this new species versus 1.0 or little more in S. (G.) sofiani ).

Figures

FIGURE 9. Female of Simulium (Gomphostilbia) thituyenae sp. nov. A, third segment of maxillary palp with sensory vesicle (left side, front view); B, cibarium (front view); C, tibia of hind leg (left side; outer view); D, basitarsus and second tarsomere of hind leg (left side; outer view); E, claw; F, sternite 8 and ovipositor valve (right half; ventral view); G, genital fork (ventral view); H & I, paraprocts and cerci (left side; H, ventral view; I, lateral view); J, spermatheca. Scale bars. 0.1 mm for C and D; 0.02 mm for A, B and F – J; 0.01 mm for E.

FIGURE 10. Pupa of Simulium (Gomphostilbia) thituyenae sp. nov. A, frontal trichome; B, facial trichome; C – F, thoracic trichomes (C, anterodorsal; D, anterolateral; E, mediolateral; F, ventrolateral); G, anterior part of thorax and gill filaments (right side; outer view); H, terminal hooks (caudal view); I, cocoon (dorsal view). Scale bars. 1.0 mm for I; 0.1 mm for G; 0.02 mm for A – F and H.