Simulium (Simulium) serenum Hunag & Takaoka, 2009

Takaoka, Hiroyuki & Huang, Yao-Te, 2018, A new black fly species of Simulium (Simulium) (Diptera: Simuliidae) from Taiwan, Zootaxa 4422 (1), pp. 141-150 : 147-149

Simulium (Simulium) serenum Hunag & Takaoka, 2009

Simulium (Simulium) serenum Hunag & Takaoka, 2009: 33 –37 (Female and pupa).

This species was described from Taiwan and was placed in the S. griseifrons species-group (Huang and Takaoka, 2009). It was later transferred to the S. crocinum species-group ( Takaoka, 2017). The male of this species is here described for the first time based on four males reared from pupae collected from Taiwan. The pupa of S. serenum is easily identified by its cocoon bearing a deep anterodorsal cleft medially and a large anterolateral window on each side.

Male. Body length 3.0– 3.4 mm. Head. As wide as thorax. Upper eye medium brown, with large facets in 19 vertical columns and in 20 horizontal rows. Clypeus brownish black, thickly white pruinose, moderately covered with dark-brown hairs along lateral margins and near ventral margin except medial portion widely bare. Antenna composed of scape, pedicel and nine flagellomeres, dark yellow to light brown except scape and base of first flagellomere whitish yellow and apical four or five flagellomeres medium brown; first flagellomere elongate, 2.0 times as long as second one. Maxillary palp light to medium brown; proportional lengths of third, fourth, and fifth segments 1.0:1.1–1.2:3.2; third segment ( Fig. 4A ) of moderate size; sensory vesicle ( Fig. 4A ) small, ellipsoidal (0.21–0.23 times as long as third segment), and with small opening. Thorax. As in male of S. taichungense sp. nov. Legs. Foreleg: coxa whitish yellow; trochanter yellow to dark yellow; femur yellow to dark yellow with apical cap medium brown; tibia widely white on outer surface except extreme apical cap dark brown, though medium to dark brown on inner surface; tarsus dark brown to brownish black, with moderate dorsal hair crest; basitarsus greatly dilated, 6.0–6.5 times as long as its greatest width. Midleg: coxa dark brown except posterolateral surface brownish black; trochanter dark yellow except base yellowish white; femur yellow; tibia yellowish white to yellow; tarsus medium brown except basal three-fifths of basitarsus yellow. Hind leg: coxa dark brown; trochanter yellow; femur yellow except apical cap dark brown; tibia dark brown except base whitish yellow; tarsus medium to dark brown except basal half of basitarsus yellow (though extreme base slightly darkened) and basal half of second tarsomere yellow; basitarsus ( Fig. 4B ) much enlarged, gradually widened from base to apical two-fifths, then narrowed to apex, 4.6–4.9 times as long as its greatest width, and 0.8 and 0.8 times as wide as greatest widths of hind tibia and femur, respectively; calcipala ( Fig. 4B ) small, nearly as long as wide, 0.35 times as wide as greatest width of basitarsus; pedisulcus ( Fig. 4B ) well developed. Halter . White except basal portion darkened. Wing. Length 2.4– 2.5 mm. Other features as in male of S. taichungense sp. nov. Abdomen. Basal scale brownish black, with fringe of dark long hairs. Dorsal surface of abdomen dark brown to brownish black, with dark short hairs; segments 2 and 5– 7 each with pair of silvery iridescent spots dorsolaterally, those on segment 2 broadly connected in middle to each other. Ventral surface dark brown except segments 2–6 grayish. Genitalia. Coxite in ventral view ( Fig. 4C ) quadrate, nearly as long as wide. Style in ventral view ( Fig. 4C ) elongate, 1.7–1.9 times as long as coxite, widest near base, tapered toward middle, then slightly widened to round apex, and with short slender subapical spine; style in ventrolateral view ( Fig. 4D ) tapered in basal one-third or little more, then slightly widened toward near apex, with round apex; style in medial view ( Fig. 4E ) with elongate triangular basal projection having several small spines on anterior surface. Ventral plate in ventral view ( Fig. 4C ) well sclerotized, with body nearly flat, rounded posteriorly, 0.6 times as long as wide, and covered with many minute setae medially; arms divergent; ventral plate in lateral view ( Fig. 4F ) covered with many microsetae medially; ventral plate in caudal view ( Fig. 4G ) with body somewhat produced ventrally and dorsally. Median sclerite in lateral view ( Fig. 4F ) arising slightly anterior to anterior margin of body of ventral plate, directed posterodorsally; median sclerite in posteroventral view ( Fig. 4H ) plate-like, nearly parallel-sided in middle, then somewhat widened apically. Paramere in posterolateral view ( Fig. 4I ) with enlarged basal portion and with several distinct hooks and several smaller ones. Aedeagal membrane ( Fig. 4J ) moderately covered with minute needle-like setae, and with moderately pigmented dorsal plate in form of horizontal bar ( Fig. 4K ). Abdominal segment 10 ( Fig. 4L, M ) without distinct hairs on ventral surface. Cercus ( Fig. 4L, M ) small, rounded, with 10–18 distinct hairs.

Specimens examined. Four males (with their associated pupal exuviae and cocoons) in 80% ethanol, collected from a small stream (width 0.5 m, water temperature 21˚C, shaded, elevation 761 masl, 23°42'11.3" N, 120°46'56.3" E), No.47, Xingchan Road , Lugu Township, Nantou County, Taiwan, 5-X-2013, by Huang, Y.T.

Remarks. The male of S. serenum is similar to those of S. ufengense and S. taichungense sp. nov. in many characters but is barely distinguished from S. ufengense by the length ratio of the first antennal flagellomere against the second one, 2.0 (1.6 in S. ufengense ), and the length ratio of the body of the ventral plate against its greatest width, 0.6 (0.8 in S. ufengense ); and from S. taichungense sp. nov. by the length ratio of the fore basitarsus against its greatest width, 6.0–6.5 (5.1 in S. taichungense sp. nov.) and the style with a subapical spine (absent in S. taichungense sp. nov.).

Figures

FIGURE 4. Male of Simulium serenum. (A) Third segment of maxillary palp with sensory vesicle (right side; front view). (B) Hind basitarsus and second tarsomere showing calcipala and pedisulcus (left side; outer view). (C) Coxites, styles and ventral plate (ventral view). (D) and (E) Styles (right side; D, ventrolateral view; E, medial view). (F) Ventral plate and median sclerite (lateral view). (G) Ventral plate (caudal view). (H) Median sclerite (caudal view). (I) Paramere (left side; posterolateral view). (J) Aedeagal membrane (caudal view). (K) Dorsal plate (ventral view). (L) and (M) Abdominal segment 10 and cerci (right half; L, lateral view; M, caudal view). Scale bars: 0.1 mm for B; 0.02 mm for A and C–M.