Simulium

Phasuk, J., Chanpaisaeng, J., Adler, P. H. & Courtney, G. W., 2005, Chromosomal and morphological taxonomy of larvae of Simulium (Gomphostilbia) (Diptera: Simuliidae) in Thailand, Zootaxa 1052, pp. 49-60 : 57-58

Simulium sp. nr. s heilae Takaoka and Davies 1995

This species belongs to the S. ceylonicum group on the basis of an enlarged basitarsus in the male. The male is similar to that of S. sheilae in the coloration of the hind tibia and basitarsus, which are mostly dark, leaving a pale portion at the base. However, this species differs from S. sheilae by having plate­like terminal hooks in the pupa and minute setae on the larval abdomen. Most larval specimens of S. sp. nr. sheilae had sparse, minute, delicate setae with 2 or 3 branches (rarely unbranched) on the dorsal surface of the posterior abdominal segments ( Fig. 2 H); however, some specimens had mostly unbranched setae and were, therefore, similar to larvae of S. asakoae . The eight gill filaments are similar to those of S. sheilae ( Fig. 3 F). The postgenal cleft is moderately deep, about 3 times as long as the postgenal bridge ( Fig. 4 E). The adult legs also differ in their dark coloration.

For this species, 79 larvae were analyzed. The centromere region of chromosome I is expanded, whereas the centromere regions of chromosomes II and III are not. The IIS arm has the bulge and ring of Balbiani in the same locations as in S. sheilae ( Figure 1 I).

Figures

FIGURE 1. Idiograms of chromosome arm IIS for 12 Simulium species in subgenus Gomphostilbia from Khao Yai National Park, showing relative locations of Ce, centromere; RB, ring of Balbiani; Bu, bulge; Sh, shoestring. A, Simulium angulistylum. B, S. decuplum. C, S. dentistylum. D, S. gombakense. E, S. siamense. F, S. sp. A. G, S. asakoae. H, S. sheilae. I, S. sp. nr. sheilae. J, S. novemarticulatum. K, S. sp. B. L, S. sp. C.

FIGURE 2. Photographs of setae on abdominal cuticle of Simulium species in subgenus Gomphostilbia. A, Simulium angulistylum. B, S. decuplum. C, S. dentistylum. D, S. siamense. E, S. sp. A. F, S. asakoae. G, S. sheilae. H, S. sp. nr. sheilae. I, S. novemarticulatum. J, S. sp. B.

FIGURE 3. Photographs of gill filaments of Simulium species in subgenus Gomphostilbia. A, Simulium angulistylum. B, S. sp. A. C, S. novemarticulatum. D, S. siamense. E, S. sheilae. F, S. sp. nr. sheilae.

FIGURE 4. Photographs of postgenal clefts of Simulium species in subgenus Gomphostilbia. A, Simulium asakoae. B, S. gombakense. C, S. sheilae. D, S. dentistylum. E, S. sp. nr. sheilae. F, S. sp. A.