Simulium (Montisimulium) schizostylum Chen and Zhang

Han-Bin, Chen, Guo-Sheng, Lian & Chun-Lin, Zhang, 2011, A faunal summary of Simulium (Montisimulium) with descriptions of five new species from China (Diptera: Simuliidae), Zootaxa 3017, pp. 51-68 : 58-60

Simulium (Montisimulium) schizostylum Chen and Zhang , sp. nov.

( Figs. 20–31 )

Female. Body length about 3.6mm. Wing length about 3.0 mm.

Head. Narrower than thorax. Frons brownish black, covered with golden pubescence and brown hairs. Clypeus black, thickly whitish grey pruinose and covered with several brown hairs. Frontal ratio 7.8:5.2:9.7; frontal-head ratio 7.8:29.7. Antenna composed of 2+9 segments, all of which are brownish black except brownish yellow scape. Maxillary palp with 5 segments, proportional length of 3rd to 5th segments 6.8:4.5:11.2?sensory vesicle elongate, ca. twice as long as wide and about 2/3 as long as 3rd segment. Maxilla with 8 inner teeth and 7 outer ones. Mandible with 26 inner small teeth and lacking outer ones.

Thorox. Scutum brown, densely covered with golden yellow pubescence intermixed with some long black hairs on prescutellar area. Scutellum brownish black grey-dusted and with sparse, erect black hairs. Postscutellum brown, grey-dusted and bare. Pleural membrane and katepisternum bare. Legs: All coxae and trochanters pale brown except hind coxa brown. All femora yellow except distal 1/4–1/3, which is brown. All tibiae brown with median large portion yellow. All tarsi brown except hind basitarsus and basal 1/3 of second tarsomeres yellow. Fore basitarsus slender, about 8.0 times as long as its greatest width. Hind basitarsus nearly parallel-sided, about 7.5 times as long as wide. Calcipala and pedisulcus moderately developed. Each claw with large basal tooth. Wing. Costa with spinules as well as hairs, subcosta hairy; basal portion of radius fully haired. Hair tuft at base of costa and on stem vein blackish brown.

Abdomen. Basal scale brown with a fringe of brownish black hairs. Terga dark brownish and covered with dark hairs. Genitalia: Sternite 8 with about 35 long hairs on each side. Anterior gonapophyses nearly triangular, covered with microsetae and a few short setae; inner margins nearly straight and narrowly sclerotized; posteromedian corner rounded. Genital fork with slender sclerotized stem; arms with sclerotized ridge but lacking any prominent projections directed forward. Spermatheca elliptical and with reticulate pattern.

Male. Body length 3.8–4.0 mm. Wing length about 3.5 mm.

Head. Width equal to that of female. Upper-eye consisting of 14 vertical and 15 horizontal rows of large facets. Clypeus black, grey-dusted, covered with long black hairs and a few pale hairs. Antenna composed of 2+9 segments, 1st flagellomere elongated, being about 2.2 times as long as following one. Maxillary palp with 5 segments, 3rd segment somewhat enlarged and with small sensory vesicle, which is about 0.20 length of respective segment.

Thorax. Nearly as in female except hind basitarsus slightly inflated, W:L ratio 1.0:4.8 and subcosta of wing bare.

Abdomen. Nearly as in female. Genitalia. Gonocoxite subconical, longer than wide. Gonostylus about 0.7 length of gonocoxite with bifid tip, abruptly narrowed apically and with a stout apical spine; when viewed ventrolaterally, gonostylus with a distinct outwardly directed subapical rounded projection which has 4 or 5 small stout teeth. Ventral plate lamellate, subrectangular in shape, with distal median margin deeply concave, posterolateral corner rounded; lateral margin nearly parallel-sided; arms short, well sclerotized and divergent, each with a sclerotized peg-like process directed backward. Parameres each with 3 strong parameral teeth and several small teeth. Median sclerite slender with somewhat enlarged end.

Pupa. Body length about 4.5 mm.

Head and thorax. Nearly as in S. (M.) xinzhouense , sp. nov.

Abdomen. Arrangement of setae, spines and hairs of dorsal and ventral surfaces of abdomen similar to those of S. (M.) xinzhouense sp. nov. and S. (M.) luliangense sp. nov, but cocoon with longer anterodorsal projection which is about 1/2 of cocoon.

Mature larva. Body length about 7.0 mm. Cephalic apotome positive. Antenna slightly longer than latral fan and with 3 segment and a terminal sensory organ; proportional lengths of 3 segment from base to tip 7.5:5.4:3.4; much longer than stem of labral fan. Each labral fan with 28–30 main rays. Mandible with a large and a small madibular tooth but lacking supernumerary serrations. Hypostomium with a row of 9 apical teeth and its corner and median teeth much longer than 3 intermediate teeth on each side; hypostomal bristles 4–6 in number, lying subparallel to lateral margin on each side. Postgenal cleft very minute, M-shaped, about 1/3 length of postenal bridge. Thoracic and abdominal integument bare. Rectal gill lobes compound. Anal sclerite X-shaped, with anterior arms short about 0.8 times as long as posterior ones. Posterior circlet with about 80 rows of up to 16 hookets per row. Ventral papillae well developed.

Type materials. Holotype Ƥ, reared from pupa, slide-mounted, collected from stone in a rapid current at Luya Mountain (38°64ʹN, 112°60ʹE, 1500m), 13, 3Ƥ, 8 pupae and 2 larvae, by Lian Guo-sheng, same data as holotype.

Distrution. Shanxi Province, China.

Remarks. The present new species is distinctive in having 10 pupal filaments, which has been reported only in 7 named species, S. (M.) alpinum (Rubtsov, 1947) . S. (M.) decafile Rubtsov, 1976 , S. (M.) peskovi Ismagulov and Koshkimbaev, 1996 , S. (M.) decimfiliatum ( Rubtsov, 1956) , S. (M.) tatianae Bodrova, 1981 , S. (M.) violovitshi (Rubtsov, 1962) and S. (M.) schevyakovi (Dorogostajsky, Rubtsov and Vlasenko, 1935) . Based on the filament branching pattern and the cocoon with an anterodorsal projection, this new species seems to be most closely related to S. (M.) decafile Rubtsov, 1976 from Kazakhstan. The new species, however, can be readily separated from S. (M.) decafile by several characters, such as the large sensory vesicle in the female; the shape of the gonostylus, ventral plate and median sclerite in the male; the cocoon with a very long anterodorsal projection in the pupa; and the shape of the postgenal cleft and the number of hypostomal bristles in the larva.

Etymology. The specific name was given for the shape of the male gonostylus.

Figures

FIGURES 20 – 31. S. (M.) schizostylum Chen and Zhang, sp. nov. 20. Female genitalia; 21. Female cibarium; 22. Female sensory vesicle; 23. Gonocoxite and gonostylus of male; 24. Ventral plate; 25. Median sclerite; 26. Paramere; 27. Cocoon in dorsal view; 28. Filaments; 29. Larval head capsule in ventral view; 30. Larval mandible; 31. Larval anal sclerite.