The male, pupa and mature larva of Simulium (Asiosimulium) wanchaii Takaoka & Choochote, one of the four species of the small Oriental black fly subgenus Asiosimulium, are described for the first time based on samples collected from Thailand. The male S. (A.) wanchaii is characterized based on the enlarged hind basitarsus and the ventral plate which is much wider than long. The pupa and larva are characterized by the gill with 19 filaments and the deep postgenal cleft, respectively. Keys are provided to identify all the four species of the subgenus Asiosimulium for females, males, pupae and mature larvae.

The chromosomal relationships of Simulium arakawae, a black fly of medicalveterinary importance, are resolved relative to other members of the Simulium venustum species group and to the standard reference map for the subgenus Simulium. Simulium arakawae differs from the subgeneric standard by eight fixed inversions, apparently none of which are shared with any of the other 17 chromosomally studied nominal members of the group. The chromosomal features that indicate group membership might have been lost in S. arakawae, particularly if they were polymorphic in an ancestor.

Simulium (Gomphostilbia) sofiani sp. nov. is described on the basis of reared adult female, male, pupal and larval specimens collected from Cameron Highlands, Pahang state, Malaysia. This new species is placed in the ceylonicum species-group within the subgenus Gomphostilbia and is easily distinguished from all the related known species by the combination of the following characteristics: an elongate sensory vesicle and yellow hair tuft on the stem vein of the wing in the female, the greater number of large upper-eye facets (15 or 16 vertical columns and 15 or 16 horizontal rows) and almost entirely darkened hind basitarsus in the male, and the gill bearing a long common basal stalk and 8 filaments arranged as [(1+2)+ (1+2)] +2 filaments from dorsal to ventral in the pupa.

A preliminary survey of larvae and pupae of black flies (Diptera: Simuliidae) was conducted in three recreation parks [Templer Recreation Park (TRP), Congkak River Forest Reserve (CRFR) and Ampang Forest Reserve (AFR)] located in Selangor State, which is located 18 to 35 km from Kuala Lumpur city center, Malaysia. This study was initiated to determine the distribution and abundance of filarial vectors, Simulium spp. A total of 12 species of black flies belonging to three subgenera (Gomphostilbia, Simulium and Nevermannia) were collected. Simulium (Simulium) nobile was incriminated as the most dominant species in all recreation parks. This study is a first report on the distribution and abundance of black flies obtained from recreation parks in Malaysia.

Simulium (Wallacellum) tuyense Takaoka, one of the 14 Philippine species in the subgenus Wallacellum Takaoka, is a rare species in having the pupal antennal sheath with a row of stout spines on the apex of each protuberance corresponding to flagellomeres 2–9. The female of this species is described for the first time based on specimens from Mindoro, the Philippines. It is characterized by an elongate sensory vesicle, triangular ovipositor valve, genital fork with two projections, and paraproct not produced anteriorly. This species is morphologically indistinguishable in the female, as in the male and pupa, from S. (W.) yonakuniense Takaoka from Yonakuni Island, Japan and Lanyu Island, Taiwan. Taxonomic notes on the female of this species relevant to those of related species are provided. Collection data to validate earlier distribution records of S. (W.) tuyense and S. (W.) suyoense Takaoka from Mindanao are presented.

The males of Simulium (Gomphostilbia) miblosi Takaoka in the S. epistum species-group, and S. (G.) apoense Takaoka in the S. ceylonicum species-group, both from Mindanao, the Philippines, are described for the first time. The male of S. (G.) miblosi is characterized by the hind tibia yellowish white on the basal three-fifths, elongate calcipala 1.5 times as long as its basal width, and ventral plate triangular ventrally (0.74 times as high as its greatest width) when viewed caudally. Tubercles on the frons and trichomes on the head and thorax of the pupa of this species are illustrated for the first time. The male of S. (G.) apoense is characterized by the small sensory vesicle 0.16–0.19 times as long as the third palpal segment, and enlarged hind basitarsus 1.0 and 1.2–1.3 times as wide as the hind tibia and femur, respectively. Taxonomic notes of these two species relevant to related species in each species-group are given.

Simulium (Simulium) thimphuense sp. nov. is described from a pupa and a mature larva in Bhutan. This new species is placed in the S. multistriatum species-group, and is characterized by the pupal gill with eight thread-like filaments divergent basally at an acute angle when viewed laterally and the cocoon slipper-shaped with several small openings anterolaterally. Four species of Simulium (Simulium) are newly recorded from Bhutan: S. barraudi Puri in the S. multistriatum species-group, S. nodosum Puri in the S. nobile species-group, S. chiangmaiense Takaoka & Suzuki in the S. striatum species-group and S. himalayense Puri in the S. variegatum species-group. Our study increases the number of black fly species known from Bhutan from 18 to 23.

Five species of black flies are newly recorded from Myanmar: Simulium (Gomphostilbia) gombakense Takaoka & Davies, S. (G.) siamense Takaoka & Suzuki, S. (Simulium) chanyae Takaoka & Choochote, S. (S.) nigrifacies Datta and S. (S.) tani Takaoka & Davies (complex). This increases the number of species of black flies from Myanmar from 23 to 28. The male and pupa of S. (S.) chanyae are described for the first time. The pupa of this species is characterized by having the wall-pocket-shaped cocoon without anterolateral windows, separating it from most other species of the Simulium multistriatum speciesgroup.

Simulium chayamaritae Takaoka & Srisuka from Thailand belongs to the Simulium darjeelingense species-group of Simulium (Simulium) (Diptera: Simuliidae). The female of this species is described for the first time based on a female reared from a pupa collected from Chiang Mai, Thailand. It is characterized by the sensory vesicle elongate and the inner margins of the arms of the genital fork divergent, then convergent apically. It is similar to the female of S. eshimai Takaoka & Adler of the same speciesgroup from Vietnam. Taxonomic notes are given to separate it from two other species of the S. darjeelingense species-group from India and Malaysia, and 28 of 31 other species of the subgenus Gomphostilbia recorded from Thailand.

The Simulium gombakense species-group, one of the 15 species-groups of the subgenus Gomphostilbia Enderlein, is small, being represented by only 12 species, all of which are distributed in the Oriental Region. It is characterized by the pupal gill composed of an inflated structure and eight or ten slender filaments. Among the 12 species, S. sachini Takaoka & Henry, and S. williei Takaoka & Thapa were originally described from two pupae, and one pupa and two larvae, respectively, from Darjeeling, India. In the present paper, the adult females and males of these species are described for the first time from specimens reared from pupae collected at the type locality. Simulium sachini is distinctive in the female by the claw with a medium-sized basal tooth, and in the male by the somewhat enlarged, spindleshaped hind basitarsus and ventral plate with its ventral margin much depressed medially, while S. williei is characterized by the small number of male upper-eye (large) facets in 12 vertical columns and 13 or 14 horizontal rows and ventral plate much produced posteroventrally. Taxonomic notes are given to separate these two species in the adult stage from their related species.