Simulium (Gomphostilbia) hmongense Takaoka

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 : 26-30

Simulium (Gomphostilbia) hmongense Takaoka & Ya’cob sp. nov.

Pharate Male. Only following characters observed. Upper-eye facets in 17 vertical columns and 17 horizontal rows. Antenna composed of scape, pedicel and nine flagellomeres. Sensory vesicle small and rounded. Hind basitarsus ( Fig. 9 A) enlarged. Costa with spinules and hairs. Basal portion of radius haired.

Pupa. Body length 3.4 mm. Head. Integument yellow, moderately covered with small round tubercles; antennal sheath without any protuberances; frons with three pairs of unbranched long trichomes with coiled or straight apices ( Fig. 9 B); face with pair of unbranched medium-long trichomes with straight apices ( Fig. 9 C); three frontal trichomes on each side arising close together, subequal in length to one another and somewhat longer than facial one. Thorax. Integument yellow except narrow mediolongitudinal portion of dorsal surface darkened, sparsely covered with small round tubercles, with three long anterodorsal trichomes with coiled apices ( Fig. 9 D), two long anterolateral trichomes (anterior trichome somewhat shorter than posterior one and with straight apex, posterior trichome with coiled apex) ( Fig. 9 E), mediolateral trichome lost, and three ventrolateral trichomes with straight apices (one medium-long, two short) ( Fig. 9 F), on each side; all trichomes unbranched. Gill ( Fig. 9 G) composed of eight slender thread-like filaments, arranged as [(2+1)+(2+1)]+2 from dorsal to ventral; common basal stalk medium-long, 0.8 times length of interspiracular trunk, having somewhat swollen basal fenestra at base; dorsal and middle triplets sharing medium-long common stalk 0.9 times length of common basal stalk; dorsal triplet composed of one individual and two paired filaments with short primary and secondary stalk in left gill or composed of three individual filaments arising at same level from short stalk in right gill; primary stalk directed inward and slightly upward, thus appearing to be hidden behind middle triplet; middle triplet directed forward, composed of one individual filament and two paired filaments with long primary and medium-long secondary stalks; stalk of ventral pair directed downward, then forward, 0.9 times as long as primary stalk of middle triplet and 1.3 times length of interspiracular trunk; stalk of ventral pair 0.8 times as thick as common stalk of dorsal and middle triplets, 1.1 and 1.3 times as thick as primary stalks of middle and dorsal triplets respectively; all filaments grayish light-brown, gradually tapered toward apices; lengths of filaments probably little longer than 3.0 mm (exact length of filaments not measurable due to loss of apical portions of all filaments); filaments of dorsal and middle triplets subequal in length and thickness to one another, and appearing to be slightly shorter and thinner than ventral paired filaments; cuticle of all filaments with well-marked annular ridges and furrows, which are, though, becoming less distinct apically, and densely covered with minute tubercles, relatively larger ones on ridges. Abdomen. Dorsally, segments 1–4 grayish light-brown, segment 9 yellowish, other segments unpigmented; segment 1 with one unbranched slender medium-long hair-like seta ( Fig. 9 H) on each side; segment 2 with one unbranched slender short hair-like seta ( Fig. 9 I) and four short somewhat spinous setae submedially near posterior margin on each side; segments 3 and 4 each with four hooked spines and one short somewhat spinous seta near posterior margin on each side; segments 5–8 each with two unbranched short setae near posterior margin on each side; segments 5–9 each comb-like groups of minute spines near anterior margin; segments 6–9 each with spinecombs in transverse row on each side; segment 9 with pair of small narrow blunt terminal hooks with rugged surface apically ( Fig. 9 J, K). Ventrally, segment 4 with one unbranched hook and few unbranched short setae on each side; segment 5 with pair of bifid hooks submedially and few unbranched short 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 unbranched short slender setae on each side; segments 4–8 each with comb-like groups of minute spines. Each side of segment 9 with two grapnel-shaped hooklets. Cocoon ( Fig. 9 L). Wall-pocket-shaped, moderately and thinly woven with no spaces in webs, widely extended ventrolaterally; anterior margin somewhat thickly woven, with long anterodorsal projection directed forward; posterior half with floor roughly woven; individual threads partially visible; 4.0 mm long by 3.6 mm wide.

Mature larva. Body length 5.0– 5.5 mm. Body creamy except abdominal segments 1–3 greenish and dorsal and dorsolateral surface of abdominal segments 4–9 light ochreous, with color markings as follows: thoracic segment 1 with reddish-brown transverse band (though disconnected ventromedially), dorsal surface of thorax thinly pinkish, ventral surface of thoracic segments 2 and 3 reddish brown, abdominal segment 3 thinly reddish brown entirely or partially or not, abdominal segments 4–8 entirely or partially reddish brown dorsally, dorsolaterally and ventrally (in particular markings on dorsal surface of segments 5 and 6 distinct). Head. Head capsule whitish yellow to yellow, with faint positive head spots, and sparsely covered with unpigmented minute setae (though moderately on dorsal surface). Antenna composed of three articles and apical sensillum, longer than stem of labral fan; proportional lengths of first, second, and third articles 1.0:0.9–1.0:0.9. Labral fan with 42–44 primary rays. Mandible ( Fig. 10 A) with three comb-teeth decreasing in length from first tooth to third; mandibular serration composed of two teeth (one medium-sized, one small) (left mandible in one larva with additional small tooth at base of major tooth); major tooth at acute angle against mandible on apical side; supernumerary serrations absent. Hypostoma ( Fig. 10 B) with row of nine apical teeth, of which median tooth is slightly longer than each corner tooth; lateral margin smooth; four hypostomal bristles per side lying slightly divergent posteriorly from lateral margin. Postgenal cleft ( Fig. 10 C) short, nearly quadrate, 0.9 times as long as wide, and 0.7 times length of postgenal bridge. Cervical sclerites composed of pair of yellow small rod-like pieces. Thorax and Abdomen. Thoracic proleg without hairs; thoracic cuticle bare; abdominal cuticle bare except last abdominal segment moderately covered with colorless unbranched setae on each side of anal sclerite (even down to base of ventral papilla on each side); thorax and abdomen without dorsal protuberances. Rectal scales present, unpigmented. Rectal organ compound, each of three lobes with several finger-like secondary lobules (exact number of secondary lobules uncountable). Anal sclerite of usual X-form, with anterior arms 1.2 times length of posterior ones, broadly sclerotized at base; no sensilla on broad base and posterior to posterior arms; accessory sclerite absent. Last abdominal segment with pair of large conical ventral papillae. Posterior circlet with 70 rows of hooklets with up to 12 hooklets per row.

Type material. HOLOTYPE: Pupa (pharate male) in 80% ethanol, labeled in a vial as [ UMSRP: Vietnam 0 25, Holotype, Simulium (G.) hmongense, Pharate male, coll. Vietnam, 20-XII-2014, Takaoka et al.], collected from a small stream (width 0.2 m, depth 2 cm, bottom rocky, water temperature 7.0˚C, partially shaded, elevation 1,893 m, 22˚21’28.378”N/103˚45’52.084”E) slowly flowing in shrub, Lai Chau, Sapa, Lao Cai Province, northern Vietnam , 20-XII-2014, by H. Takaoka, M. Sofian-Azirun, Z. Ya’cob, C.D. Chen & K.W. Lau. PARATYPES: Two mature larvae in 80% ethanol, labeled in a vial as [ UMSRP: Vietnam 0 25, Paratype, Simulium (G.) hmongense, Larvae , coll. Vietnam, 20-XII-2014, Takaoka et al.], collected from a stream (width 0.2 m, depth 5 cm, bottom sandy and muddy, water temperature 8.0˚C, exposed to the sun, elevation 1,925 m, 22˚21’11.767”N/103˚46’28.309”E) slowly flowing in shrub in grassland, Lai Chau, Sapa, Lao Cai Province, northern Vietnam , 20-XII-2014, by H. Takaoka, M. Sofian-Azirun, Z. Ya’cob, C.D. Chen & K.W. Lau.

Biological notes. The pupa and larvae of this new species were collected from plastic sheets in the current. Associated species were S. (M.) nigrofilum sp. nov., S. (N.) maeaiense and S. (S.) daoense sp. nov.

Etymology. The species name hmongense refers to the land in which the Hmong tribe lives.

Remarks. This new species may be assigned to one of the three species-groups ( S. asakoae , S. ceylonicum and S. darjeelingense species-groups) of the subgenus Gomphostilbia , redefined by Takaoka (2012), by having the enlarged male hind basitarsus ( Fig. 9 A). This new species is placed in the S. asakoae species-group due to the similarity of the unique pupal terminal hooks ( Fig. 9 J, K) to those of S. (G.) lurauense Takaoka, Sofian-Azirun & Hashim from Peninsular Malaysia and S. (G.) thituyenae Takaoka & Pham from Vietnam, both of which are members of the S. asakoae species-group (Takaoka et al. 2011, 2015a).

This new species is characterized by the greater number of male upper-eye facets in 17 vertical columns and 17 horizontal rows, pupal thoracic integument sparsely covered with tubercles, middle triplet of the gill with a long primary stalk ( Fig. 9 G), cocoon with a long anterodorsal projection ( Fig. 9 L), and small larval postgenal cleft ( Fig.

10C). Among the species of the S. asakoae species-group, only two species, S. (G.) chiangdaoense Takaoka & Srisuka from Thailand and S. (G.) fuscidorsum Takaoka & Ya’cob from Vietnam, have the cocoon with a long anterodorsal projection ( Takaoka and Srisuka 2009; Takaoka et al. 2015a). However, S. (G.) chiangdaoense differs by having the number of male upper-eye facets in 13 or 14 vertical columns and 15 or 16 horizontal rows, pupal thoracic integument moderately covered with tubercles and middle triplet of the pupal gill with a short primary stalk, and S. (G.) fuscidorsum differs by having the pupal thoracic integument moderately covered with tubercles, long common basal stalk of the pupal gill, and shape of the terminal hooks, of which the outer margin is longer than the inner one and crenulated.

Out of seven species among the S. ceylonicum species-group, which have the cocoon with a long anterodorsal projection, S. (G.) inthanonense Takaoka & Suzuki described from Thailand ( Takaoka and Suzuki 1984) has a similar number of male upper-eye facets (16 vertical columns and 16 horizontal rows) and small larval postgenal cleft, but is distinguished from this new species by the ellipsoidal male sensory vesicle, arrangement of the pupal gill filaments (length ratio of the primary stalk of the middle triplet against the stalk of the ventral pair is 0.6–0.7, whereas it is 1.1 in this new species) and shape of the terminal hooks, of which the outer margin is much longer than the inner one. Another species, S. (G.) ogatai (Rubtsov) described from Japan ( Rubtsov 1959 –1964), shares a similar number of male upper-eye facets in 14 or 15 vertical columns and 16 horizontal rows, and similar small pupal terminal hooks, but differs by the arrangement of the pupal gill filaments (length ratio of the primary stalk of the middle triplet against the stalk of the ventral pair is 0.4–0.5, whereas it is 1.1 in this new species), and dorsal surface of pupal abdominal segments 1–4 unpigmented. (Characters of S. (G.) ogatai used here are based on specimens collected in Gifu, Japan, in July 17, 2011 by Dr. Y. Otsuka).

All five species of the S. darjeelingense species-group have simple wall-pocket-shaped cocoons, thus differing from this new species.

Figures

FIGURE 9. Male and pupa of Simulium (Gomphostilbia) hmongense sp. nov. A, Hind basitarsus and second tarsomere of male leg (left side; outer view); B & C, Pupal cephalic trichomes (B, frontal; C, facial); D – F, Pupal thoracic trichomes (D, anterodorsal; E, anterolateral; F, ventolateral); G, Anterior part of pupal thorax and gill filaments (left side; outer view); H & I, Hair-like setae on dorsal surface of pupal abdomen (H, on segment 1; I, on segment 2); J & K, Pupal terminal hooks (J, lateral view; K, caudal view); L, cocoon (dorsal view). Scale bars. 1.0 mm for L; 0.2 mm for G; 0.1 mm for A; 0.04 mm for B – F, H and I; 0.02 mm for J and K.

FIGURE 10. Larva of Simulium (Gomphostilbia) hmongense sp. nov. A, Mandible; B, Hypostoma; C, Head capsule (ventral view). Scale bars. 0.1 mm for C; 0.02 mm for A and B.