Simulium (Gomphostilbia) maelanoiense Takaoka, Srisuka & Saeung, 2020

Takaoka, Hiroyuki, Srisuka, Wichai, Fukuda, Masako & Saeung, Atiporn, 2020, Twenty-one new species of the Simulium (Gomphostilbia) asakoae species group (Diptera, Simuliidae) in Thailand, with their genetic relationships, ZooKeys 950, pp. 51-152 : 51

Simulium (Gomphostilbia) maelanoiense Takaoka, Srisuka & Saeung sp. nov. Fig. 9

Material examined.

Holotype: Male (with its associated pupal exuviae and cocoon) (in 80% ethanol) labeled as "Holotype: Simulium maelanoiense male, QSBG col. no. 105, Thailand, 14-VII-2017, by W. Srisuka", collected from a small stream (width 25 cm, depth 2.5 cm, bed sandy, moderate flow, pH 6.8, 21.9 °C, partially shaded, elevation 974 m, 18°20'35.8"N, 98°01'23.8"E), at Tee La Chan Waterfall, Mae La Noi District, Mae Hong Son Province, Thailand, 14-VII-2017, by W. Srisuka (Coll. No. 105).

Paratypes: Two females (thoraces for DNA analysis) (with its associated pupal exuviae and cocoon) (in 80% ethanol), collected from a stream (width 110 cm, depth 12 cm, bed sandy, moderate flow, pH 6.9, 18.3 °C, partially shaded, elevation 1,446 m, 18°51'38.8"N, 99°22'15.2"E), at Kiew Fin, Muang Pan District, Lampang Province, Thailand, 6-IV-2018, by W. Srisuka (Coll. No. 36); two males (thorax of one male for DNA analysis) (with their associated pupal exuviae and cocoons) (in 80% ethanol), same data as for holotype.

Diagnosis.

Female: mandible with one tooth on the outer margin (Fig. 9A ). Male: small number of upper-eye facets in eleven vertical columns and 13 horizontal rows, and hind basitarsus (Fig. 9B ) 1.0-1.1 times as wide as the hind femur.

Description.

Female (N = 2). Body length 2.0 mm.

Head. Frontal ratio 1.9:1.0:2.7; frons:head ratio 1.0:4.9. Labrum 0.70 times length of clypeus. Maxillary palpus: proportional lengths of third, fourth, and fifth palpal segments 1.0:1.1:2.1; sensory vesicle 0.26-0.32 times length of third palpal segment. Lacinia with ten or eleven inner and 12 or 13 outer teeth. Mandible (Fig. 9A ) with 20 inner teeth and one outer tooth at some distance from tip.

Legs. Foreleg: basitarsus moderately dilated, 6.6 times as long as its greatest width. Midleg: tarsus dark brown to brownish black though basal half of basitarsus dark yellow (its border not well defined). Hind leg: coxa light brown; tibia yellowish white on basal three-fifths and light brown to brownish black on rest; tarsus brownish black except basal three-fifths (though base light brown) and basal half of second tarsomere yellowish white; basitarsus 6.9 times as long as wide, and 0.7 and 0.5 times as wide as greatest widths of tibia and femur, respectively; calcipala 0.6 times as wide as greatest width of basitarsus; claw with large basal tooth 0.44 times length of claw.

Wing. Length 2.0 mm.

Abdomen. Dorsal surface of abdomen medium to dark brown except anterior four-fifths of segment 2 ochreous.

Terminalia. Sternite 8 with 27 medium-long to long hairs together with two to four slender short hairs on each side. Ovipositor valves each moderately covered with microsetae interspersed with one to three short hairs. Paraproct in ventral view with four sensilla on anteromedial surface; paraproct in lateral view 0.6 times as long as wide, with 19 or 20 medium-long to long hairs on ventral and lateral surfaces.

Male (N = 3). Body length 2.3-2.4 mm.

Head. Somewhat wider than thorax. Upper eye medium brown, consisting of large facets in eleven (rarely ten) vertical columns and 13 horizontal rows on each side. Antenna light to medium brown except scape, pedicel, and base of first flagellomere whitish yellow; first flagellomere elongate, 1.9 times length of second. Maxillary palpus: proportional lengths of third, fourth, and fifth palpal segments 1.0:1.2:2.6; sensory vesicle 0.16-0.21 times length of third palpal segment.

Legs. Foreleg: tibia yellowish white except apical three-tenths dark brown; basitarsus moderately dilated, 6.6-7.8 times as long as its greatest width. Hind leg: coxa light brown; tibia dark brown to brownish black except little less than basal half yellowish white; tarsus (Fig. 9B ) brownish black except little more than basal two-fifths of basitarsus and basal one-third of second tarsomere yellowish white; basitarsus (Fig. 9B ) 3.6-3.8 times as long as wide, and 1.0 and 1.0-1.1 times as wide as greatest width of tibia and femur, respectively; calcipala (Fig. 9B ) slightly shorter than basal width, and 0.28 times as wide as greatest width of basitarsus.

Wing. Length 2.0-2.1 mm. Subcosta with 2-13 hairs, though rarely without hair.

Genitalia. Style in ventrolateral view (Fig. 9D ) slightly tapered toward apex, with round apex. Ventral plate in ventral view (Fig. 9C ) with basal arms of moderate length, nearly parallel-sided, then convergent apically; ventral plate in caudal view (Fig. 9F ) with ventral margin nearly straight. Cercus with 13-15 hairs.

Pupa (N = 5). Body length 2.5-3.0 mm.

Head. Integument yellow.

Thorax. Integument yellow, moderately covered with round tubercles except dorsal surface of posterior half sparsely covered with tubercles, and dorsolateral surface of posterior half almost bare. Gill (Fig. 9G ) composed of eight slender thread-like filaments, arranged as (3+3)+2 (or rarely [3+(1+2)]+2) from dorsal to ventral; common basal stalk 0.6-0.7 times length of interspiracular trunk; dorsal triplet composed of three individual filaments arising at same level, and with extremely short stalk in some pupae, middle triplet mostly composed of three individual filaments arising at same level, or rarely composed of one individual and two paired filaments with extremely short secondary stalk; stalk of ventral pair of filaments variable in length, 0.6-1.3 times length of common basal stalk, and 0.5-1.0 times length of interspiracular trunk; primary stalk of dorsal triplet lying against that of lower pair at angle of 60-80° when viewed laterally; filaments of dorsal triplet subequal in length (1.5-2.0 mm) and thickness to one another; filaments of middle triplet subequal in length (1.7-2.5 mm) and thickness, and two filaments of ventral pair subequal in length (2.5-3.6 mm) and thickness to each other and 1.4-1.8 times as thick as six other filaments of dorsal and middle triplets when compared basally.

Abdomen. Dorsally, segments 1 and 2 without minute tubercles; segment 9 with pair of wide flat terminal hooks (Fig. 9H ), of which outer margin 2.1-2.3 times length of inner margin and crenulated when viewed caudally.

Cocoon (Fig. 9I ). Dark brown, slipper-shaped, moderately woven, moderately extended ventrolaterally; anterior margin thickly woven medially, often with bulge; 3.0-3.8 mm long by 2.0-2.5 mm wide.

Mature larva. Unknown.

Etymology.

The species name, maelanoiense , refers to the district, Mae La Noi, where this species was collected.

Distribution.

Thailand (Lampang and Mae Hong Son).

Discussion.

Simulium maelanoiense sp. nov. is most similar in the male and pupa to S. sutheppuiense sp. nov. in many characters including the number of male upper-eye facets, relative width of the hind basitarsus compared to the hind tibia and femur, shape of the ventral plate when viewed caudally, and arrangement of the pupal gill. However, this new species is barely distinguished in the female from S. sutheppuiense sp. nov. by the number of the outer teeth of the mandible (one tooth in this new species versus three teeth in S. sutheppuiense sp. nov.) and the length ratio of the labrum against the clypeus (0.7 in this new species versus 0.6 in S. sutheppuiense sp. nov.).

Figures

Figure 9. Female, male and pupa of S. maelanoiense sp. nov. A female B-F male G-I pupa. A mandible (left side) B hind basitarsus and second tarsomere (left side; lateral view) C coxites, styles and ventral plate (ventral view) D style (right side; ventrolateral view) E ventral plate and median sclerite (lateral view) F ventral plate (caudal view) G gill filaments (right side; lateral view) H terminal hooks (caudal view) I cocoon (dorsal view). Scale bars: 1.0 mm (I); 0.1 mm (B, G), 0.02 mm (C-F); 0.01 mm (A, H).