Simulium ( Montisimulium ) nigrofilum Takaoka & Sofian-Azirun

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 : 61-65

Simulium ( Montisimulium) nigrofilum Takaoka & Sofian-Azirun sp. nov.

Female. Unknown.

Male. Body length 3.1 mm. Head. As wide as thorax. Upper eye with large facets in 17 vertical columns and 19 horizontal rows. Face brownish black. Clypeus brownish black, densely covered with yellow short hairs interspersed with many dark-brown hairs. Antenna composed of scape, pedicel and nine flagellomeres, brownish black except scape and pedicel medium brown and base of first flagellomere whitish yellow; first flagellomere elongate, twice length of second one. Maxillary palp with five segments, light brown except third segment dark brown and first and second segments yellow, proportional lengths of third, fourth, and fifth segments 1.0:1.1:2.1; third segment ( Fig. 26 A) slender; sensory vesicle ( Fig. 26 A) ellipsoidal, medium-long, 0.3 times length of third segment, and with small opening. Thorax. Scutum brownish black, densely covered with golden-yellow short hairs. Scutellum brownish black, with golden-yellow short hairs and dark-brown long upright hairs. Postnotum brownish black and bare. Pleural membrane bare. Katepisternum longer than deep, brownish black, and bare. Legs (coloration appearing incomplete, in particular all femora and tibia). Foreleg: coxa dark yellow; trochanter light brown; femur whitish yellow with apical cap dark brown; tibia dark brown except medial portion of outer surface paler: tarsus brownish black; basitarsus slightly flattened, 11.0 times as long as greatest width. Midleg: medium brown; trochanter light brown; femur light grayish with apical cap dark brown; tibia dark brown except median large area paler; tarsus dark brown to brownish black. Hind leg: coxa medium brown; trochanter dark yellow; femur light grayish with apical cap dark brown; tibia dark brown to brownish black except median large area paler; tarsus dark brown except basitarsus grayish to light brown; basitarsus ( Fig. 26 B) somewhat enlarged, spindleshaped, 4.3 times as long as wide, and 0.9 and 0.9 times as wide as greatest widths of tibia and femur, respectively; calcipala ( Fig. 26 B) well developed, as long as width at base; pedisulcus well developed. Wing. Length 2.2 mm. Costa with dark-brown spinules and light-brown hairs except basal patch of dark hairs mixed with yellow hairs. Subcosta with one or five hairs. Hair tuft on base of radius dark brown. Basal portion of radius fully haired. Basal cell absent. Halter . Light ochreous with basal portion darkened. Abdomen. Basal scale dark brown, with fringe of yellow long hairs. Dorsal surface of abdomen dark brown to brownish black, covered with yellow short hairs interspersed with dark hairs. Genitalia. Coxite in ventral view ( Fig. 26 C) nearly rectangular, 2.1 times as long as its greatest width. Style in ventral view ( Fig. 26 C) slender, curved inward, tapered from middle to apex, with apical spine; style in ventrolateral view ( Fig. 26 D) 0.6 times as long as coxite, nearly parallel-sided from base to middle, then tapered toward apex; style in medial view ( Fig. 26 E) boot-shaped, with apical portion twisted dorsally in form of triangular projection. Ventral plate in ventral view ( Fig. 26 C) transverse, 0.4 times as long as greatest width at base, with body narrowed posteriorly, with anterior margin produced anteromedially, posterior margin greatly concave medially, and densely covered with microsetae on medial one-third of ventral surface; basal arms short, nearly parallel-sided, though slightly convergent apically; ventral plate in lateral view ( Fig. 26 F) with apical portion of arms slightly curved dorsally; ventral plate in caudal view ( Fig. 26 G) slightly rounded ventrally, with dorsal margin greatly concave medially, densely covered with microsetae medially on posterior surface. Median sclerite ( Fig. 26 C, F, H), plate-like, narrowed toward middle, then widened toward apex, arising from level near anteromedial tip of ventral plate, and directed posteriorly. Paramere ( Fig. 26 I) with four distinct hooks. Aedeagal membrane ( Fig. 26 J) moderately covered with microsetae, and with weakly sclerotized dorsal plate in form of broad band. Ventral surface of abdominal segment 10 ( Fig. 26 K, L) with two to five distinct hairs near posterior margin on each side. Cercus ( Fig. 26 K, L) rounded, slightly produced ventrally, with eight to eleven hairs.

Pupa. Body length 3.2 mm. Head. Integument including antennal sheaths yellow, densely covered with tubercles having few to several minute secondary projections; frons with two pairs of unbranched short trichomes with straight apices (one stout, one slender) ( Fig. 27 A); face with pair of unbranched short stout trichomes with coiled apices ( Fig. 27 B); two frontal trichomes on each side arising close together, and much shorter than facial ones. Thorax. Integument yellow, densely covered with tubercles bearing few to several minute secondary projections; thorax with three short anterodorsal trichomes (two stout, with coiled apices, one slender, with straight apex) ( Fig. 27 C), two short slender anterolateral trichomes with straight apices (anterior one shorter than posterior one) ( Fig. 27 D), one short stout mediolateral trichome with straight apex ( Fig. 27 E), and three short ventrolateral trichomes with straight apices (anterior one slender, two others stout) ( Fig. 27 F) on each side; all trichomes unbranched. Gill ( Fig. 27 G) composed of 12 slender thread-like filaments, arranged in four groups (one inner, one middle dorsal, one middle ventral and one outer) arising from medium-long common basal stalk, which has transparent basal fenestra and 0.8 times length of interspiracular trunk; inner group composed of two filaments with short stalk, middle dorsal and ventral groups each composed of one individual and two paired filaments with short primary and medium-long secondary stalks, and outer group composed of two pairs of four filaments with short common stalk and medium-long secondary stalks; these two pairs lying vertically, one pair dorsal and another ventral; all filaments light brown except common basal stalk dark brown, subequal in length and thickness (though their exact length unmeasurable due to loss of apical portions) and tapered toward apices; cuticle of all filaments with well-defined annular ridges and furrows, and densely covered with minute tubercles, and with numerous darkbrown minute particles inside outer cuticular layer ( Fig. 27 H). Abdomen. Dorsally, all segments yellowish; segments 1 and 2 with minute tubercles, segment 1 with one unbranched slender short hair-like seta ( Fig. 27 I) on each side; segment 2 with one unbranched slender short hair-like seta and five short somewhat spinous setae submedially ( Fig. 27 J) 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 6–8 each with spine-combs in transverse row; segments 5–9 each with comb-like groups of minute spines near anterior margin on each side; segment 9 with pair of cone-like terminal hooks ( Fig. 27 K). Ventrally, segment 4 with 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 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; segment 9 yellowish, covered sparsely with round small tubercles. Segment 9 with three grapnel-shaped hooklets ( Fig. 27 L) on each lateral side. Cocoon ( Fig. 27 M, N). Wall-pocket-shaped, thickly woven, not extended ventrolaterally, anterodorsal margin slightly produced anteriorly but without bulge or projection; posterior two-thirds with floor moderately woven; individual threads invisible; 3.0 mm long by 1.6–1.8 mm wide.

Mature larva. Body length 6.2–6.6 mm. Body creamy except anterior and posterior surfaces of thoracic proleg, ventral surface of thoracic segments 2 and 3, and abdominal segments 1–4 light grayish-green, and with reddish-brown or ochreous markings as follows: thoracic segment 1 encircled with reddish-brown band though disconnected ventrally, thoracic segments 2 and 3 light reddish-brown dorsally and reddish brown ventrally, abdominal segment 1 encircled with light reddish-brown or ochreous band though disconnected dorsomedially, abdominal segments 2–4 each with pair of light reddish-brown or ochreous spots dorsally (though colored spots only on segments 3 and 4 in one larva and absent in one larva), abdominal segments 5–9 each with reddish-brown or ochreous markings entirely or partially covering dorsal surface, and those on segments 5 and 6 extended laterally and ventrally, though becoming lighter. Head. Head capsule yellow to dark yellow except areas in front of posterior margin on dorsal and lateral surfaces, and area above eyebrow on lateral surface much darkened, and median portion of ventral surface somewhat darkened, and with distinct head spots though anterior spots of posterolateral spots faint or absent, and sparsely covered with unpigmented minute setae (though moderately on dorsal surface); eyebrow distinct. Antenna composed of three articles and apical sensillum, longer than stem of labral fan; proportional lengths of first, second, and third articles 1.0:0.9:0.7–0.8; antennal article 2 light yellow, with three unpigmented annulations ( Fig. 27 O). Labral fan with 35 primary rays. Mandible ( Fig. 27 P) with three comb-teeth decreasing in length from first tooth to third, or second and third teeth subequal; mandibular serration composed of two teeth (one medium-sized, one small); major tooth at right angle against mandible on apical side; supernumerary serrations absent. Hypostoma ( Fig. 27 Q) with row of nine apical teeth, of which median tooth as long as or slightly longer than each corner tooth; lateral margin serrate apically; five or six hypostomal bristles per side lying slightly divergent posteriorly from lateral margin. Postgenal cleft ( Fig. 27 R) absent (or vestigial if any). Cervical sclerites composed of pair of small dark rod-like pieces. Thorax and Abdomen. Thoracic proleg without hairs; thoracic and abdominal cuticle almost bare except last abdominal segment densely covered with unbranched colorless setae on dorsolateral and lateral surfaces of each side of anal sclerite and on each lateral surface down to base of ventral papilla. 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 Xform, with anterior arms as long as or slightly longer than 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 78 or 79 rows of hooklets with up to 16 or 17 hooklets per row.

Type material. HOLOTYPE: Pharate male (with its associated pupal exuviae and cocoon) in 80% ethanol, labeled in a vial as [ UMSRP: Vietnam 0 31, Holotype, Simulium ( M.) nigrofilum, Pharate male, coll. Vietnam, 20- XII-2014, Takaoka et al.], dissected out from a pupa collected from a small stream (width 0.5 m, bottom rocky, water temperature 11.0˚C, exposed to sun, elevation 1,750 m, 22˚21’43.110”N/103˚47’19.221”E) moderately flowing in a secondary forest, 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: One pupal exuviae and three mature larvae, same data as those of the holotype . in 80% ethanol, labeled in each vial as [ UMSRP: Vietnam 0 31, Paratype, Simulium ( M.) nigrofilum , coll. Vietnam, 20-XII-2014, Takaoka et al.]

Biological notes. The pupae of this new species were collected from plastic sheets in the current. Associated species were S. ( N.) tayense sp. nov., S. ( S.) laocaiense sp. nov., S. ( S.) sapaense sp. nov. and S. ( S.) turgidum sp. nov.

Distribution. Vietnam ( Lao Cai).

Etymology. The species name nigrofilum refers to the apparently black pupal gill filaments due to numerous minute black spots ( Fig. 27 H).

Remarks. This new species is characterized by the pupal gill with 12 filaments arranged in four groups ( Fig. 27 G), and wall-pocket-shaped cocoon ( Fig. 27 M, N). In the arrangement of the pupal gill, this species is most similar to S. ( M.) angkaense Takaoka & Choochote from Thailand ( Takaoka and Choochote 2005a, 2009) and S. ( M.) nemorivagum Datta from India ( Datta 1973). This new species is distinguished from S. ( M.) angkaense and S. ( M.) nemorivagum by the male upper-eye facets in 17 vertical columns and 19 horizontal rows (20 vertical columns and 22 horizontal rows in S. ( M.) angkaense , and 12 vertical columns and 14 horizontal rows in S. ( M.) nemorivagum ), and also from S. ( M.) angkaense in the pupa by the presence of grapnel-shaped hooklets on each side of abdominal segment 9 ( Fig. 27 L).