Recent studies on the biology and ecology of adult blackflies in relation to the transmission of human onchocerciasis in Guatemala are reviewed. First, earlier studies on the transmission of the disease since its discovery by Dr. R. Robles in 1915 are outlined. Second, eleven blackfly species caught on humans are evaluated for vector status on the basis of their natural and experimental infections with third-stage larvae of Onchocerca volvulus, and Simulium ochraceum,* S. metallicum* and S. callidum are confirmed as natural vectors of the disease in Guatemala in descending order of importance, whereas S. gonzalezi, S. haematopotum, S. veracruzanum and S. horacioi are potential vectors. Third, the migration and fate of O. volvulus microfilariae ingested by female blackflies are highlighted on the basis of the findings of the cibarial armature of S. ochraceum and physiological incompatibility of S. metallicum as main barriers against microfilariae, both of which greatly decrease the number of ingested O. volvulus microfilariae developing to the third-stage larvae per female. Fourth, among many ecological factors of female blackfly populations, geographical and altitudinal distributions, habits of blood feeding, host preferences for blood feeding, preference for human body parts, parous rates, daily and seasonal fluctuations of biting activities, in particular, of parous females, gonotrophic cycle, longevity, flight range, and annual transmission potential are reviewed, and their influences on the transmission dynamics of the disease agents are considered. Fifth, effects of air temperatures on the O. volvulus-S. ochraceum complex are examined, with a special reference to the characteristic altitudinal distributions of the disease. The importance of reliable identification of both the vector blackfly species and filarial larvae found in female blackflies is emphasized to understand the transmission of the disease. [*It is now known that these two species are actually species complexes.].
The simuliid fauna of the Oriental Region is reviewed in comparison with those in five other zoogeographical regions. It is relatively young, represented by only one genus Simulium, which is regarded as the most specialized among 26 genera of the family Simuliidae. The Oriental Region has the second largest simuliid fauna with 524 species or 23.8% of the world total of 2204 extant species. This species richness is associated with a high speciation index (15.4), reflected especially by the high speciation rates of two dominant subgenera Gomphostilbia and Simulium although the number of lineages in the Oriental Region is moderate (34 or 20.6% of the total 165). The Oriental fauna has relationships with all other zoogeographical regions at the lineage level, having the highest affinity index (31.9) with the Palearctic Region. It is inferred that eight of 10 Oriental subgenera moved during the ice ages from the Palaearctic to the Oriental Regions; the subgenus Gomphostilbia evolved into 11 species-groups and underwent species radiation in the Oriental Region. On the other hand, two other subgenera, Nevermannia and Simulium, moved southward during the ice ages after evolving into species-groups. In the post-ice ages, most lineages retreated northward, with different portions of species left in the Oriental Region, although some lineages failed to retreat and survived as relict lineages in the Oriental Region.
Species of eight species-groups (seven named and one unnamed) of Simulium (Simulium) Latreille are revised chiefly based on the adult female and male genitalia. Four species-groups are each divided into more than two groups. Thus, the S. christophersi species-group is divided into two (S. christophersi and S. nebulicola species-groups), the S. griseifrons species-group into six (S. griseifrons, S. grossifilum, S. chungi, S. crocinum, S. indicum and S. yadongense species-groups), the S. malyschevi species-group into two (S. malyschevi and S. pavlovskii species-groups), and the S. melanopus species-group into three (S. melanopus, S. dumogaense and S. iridescens species-groups). The S. crassifilum species-group is merged with the S. variegatum species-group. Simulium fulvipes (Ono) of the former S. malyschevi species-group and S. dentastylum Yang, Chen & Luo of Simulium s. str. species unplaced to species-group are removed from the subgenus Simulium because their male styles are subequal in length to the coxites. A revised classification of species of the 15 species-groups including eight new species-groups of Simulium (Simulium) is presented. Keys to 20 species-groups of Simulium (Simulium) in the Oriental Region are provided for adult females and males.
Recent studies on the epidemiology and control of Guatemalan onchocerciasis, chiefly made by the Guatemala-Japan Cooperative Project on Onchocerciasis Research and Control, are reviewed. Epidemiological features of Guatemalan onchocerciasis are summarized as to characteristic altitudinal distribution of endemic areas, disease manifestation, vector taxonomy, biology and transmission dynamic of the disease. Extensive insecticide studies in the field and laboratory demonstrate that the characteristic situations of Guatemalan streams where Simulium ochraceum, the main vector of onchocerciasis, breeds require ingenious methods of larviciding. Finally, the feasibility of an area vector control is indicated by the successful control operation in the San Vicente Pacaya Pilot Area, in which a new fixed-dose larviciding method was applied.
A new black fly species, Simulium taichungense, is described on the basis of one female, one male and two pupal exuviae from Taiwan. This new species is placed in the S. crocinum species-group of Simulium (Simulium) (Diptera: Simuliidae). It is characterized by the pupal gill with six unpigmented short filaments and pupal abdomen with distinct spine-combs on the dorsal surface of segments 7-9, by which it is easily distinguished from most species in the S. crocinum species-group including two species from Taiwan: Simulium serenum Huang Takaoka and S. ufengense Takaoka. It is the third species of the S. crocinum species-group from Taiwan. In addition, the male of S. serenum is described for the first time, and intraspecific variations in a few features of the male of S. chungi Takaoka Huang of the S. chungi species-group are noted.
Two new species of black flies, Simulium mainitense and S. tukurongense, are described from Palawan, the Philippines. Both species are placed in the Simulium nitidithorax subgroup of the Simulium tuberosum species-group of Simulium (Simulium). They are characterized by the female sensory vesicle of medium length, pupal thorax covered with round tubercles, and anterodorsal trichomes on the pupal thorax longer than frontal trichomes. This combination of characters separates these two new species from S. quasifrenum Delfinado, the only previously known member of the S. nitidithorax subgroup from Palawan, and nine other related species from Sabah, Sarawak, Peninsular Malaysia and India. Simulium mainitense sp. nov. is distinguished from S. tukurongense sp. nov. in the female by the somewhat larger body size, and greater length ratio of the labrum against the clypeus; and in the pupa by the much longer gill filaments.
Indonesia is one of the megadiversity country in the world endowed with rich and unique biodiversity insects such as blackflies species (Diptera: Simuliidae). Blackflies are found almost anywhere with running water suitable as habitat for the immature stages. This family is one of the most important groups of blood-sucking insects. This study collates the records of Simulium (Diptera: Simuliidae) in previous publications related fauna of Indonesia. Based on the results of this study, there were 124 species of blackflies in Indonesian Archipelago. All species are assigned to the genus Simulium Latreille s.l., and are placed into five subgenera, i.e. Gomphostilbia Enderlein, Morops Enderlein, Nevermannia Enderlein, Simulium Latreille s.str. and Wallacellum Takaoka. Further classification into 27 species groups within the subgenera were also made. Checklists of Indonesian Simuliidae are provided including data on the distribution of each species.
Simulium (Nevermannia) ledangense sp. nov. is described from females, males, pupae and mature larvae from Peninsular Malaysia. This new species is assigned to the Simulium feuerborni species-group of the subgenus Nevermannia, and is characterized by the pupa having a very long stalk of the ventral paired gill filaments, which is almost five times longer than the interspiracular trunk and female tergites of segments 2 and 5 to 7 shiny. Taxonomic notes are given to distinguish this new species from three known species of the S. feuerborni species-group from Malaysia.
Simulium (Gomphostilbia) hiroyukii is described based on females, males, pupae and larvae collected in Mount Murud, Sarawak, Malaysia. This new species is assigned to the Simulium darjeelingense species-group of the subgenus Gomphostilbia, and is characterized by the darkened fore coxae and the pupal gill with eight long filaments, of which middle and dorsal triplets have elongated primary and secondary stalks, respectively.
Two new black fly species, Simulium (Gomphostilbia) tekamense and Simulium (Gomphostilbia) jerantutense, are described based on adult females emerged from pupae in Peninsular Malaysia, and assigned to the binuanense subgroup of the batoense species-group in the subgenus Gomphostilbia. Simulium (G.) tekamense sp. nov. is characterized in the female by the subcosta with 0-2 hairs, and presence of a deep notch on the apex of the mediolongitudinal ridge of the cibarium, and in the pupa by one of two paired gill filaments of the middle triplet much thicker than the counter filament. Simulium (G.) jerantutense sp. nov. is characterized in the female by the short claw tooth 0.46 times the length of the claw, and in the pupa by the gill filaments arranged as [2+1+(1+2)]+2 filaments from dorsal to ventral. Taxonomic notes are given to distinguish these new species from related species.
Two new blackfly species, Simulium (Gomphostilbia) azhari and Simulium (Gomphostilbia) johorense, are described based on adult females, males, pupae, and larvae collected from Peninsular Malaysia, and assigned to the parahiyangum subgroup and the duolongum subgroup of the batoense species group of the subgenus Comphostilbia, respectively. S. (G.) azhari sp. nov. is characterized in the female by the narrow frons, and in the male by the broad style and the ventral plate moderately produced ventrally. S. (G.) johorense sp. nov. is also remarkable in having the female subcosta lacking hairs or bearing a reduced number of hairs ranging from one to five. The pupae of both new species share a similar arrangement of the eight gill filaments (i.e., stalks of dorsal and middle triplets and ventral pair arising at the same level from the short common basal stalk), although relative lengths of filaments of the ventral pair to those of the dorsal and middle triplets are different between the two new species. Taxonomic notes are given to distinguish these new species from other related species. Keys to identify all 10 species of the batoense species group in Peninsular Malaysia are provided for adult females, males, pupae, and mature larvae.
Simulium (Comphostilbia) izuae sp. nov. is described from female, male, pupal, and larval specimens collected from Cameron's Highlands, Peninsular Malaysia. This new species is placed in the asakoae species-group of the subgenus Gomphostilbia. The pupa of this new species is characterized by the gill with eight long filaments arranged as (3 + 3) + 2 filaments, of which the ventral pair of filaments is borne on a stalk that is always shorter than the common basal stalk. Taxonomic notes to distinguish this new species from five other Malaysian species and 12 other species of the asakoae species-group from other countries are given. Keys to identify all 18 species of the asakoae species-group are also provided for females, males, pupae, and mature larvae.
Simulium (Asiosimulium) furvum sp. nov. (Diptera: Simuliidae) is described from female, male, pupal, and larval specimens collected from Maewa National Park, Lampang Province, Thailand. This new species represents the fourth member of the subgenus Asiosimulium Takaoka & Chochoote, one of two small black fly subgenera endemic in the Oriental Region. It is characterized by a pear-shaped spermatheca in the female; a ventral plate in the male with a laterally compressed median keel directed ventrally and with a deep notch posteromedially, and aedeagal membrane with stout spines; and by 22 gill filaments in the pupa. Taxonomic notes are provided to separate this new species from three known species, Simulium (Asiosimulium) oblongum Takaoka & Choochote and Simulium (Asiosimulium) wanchaii Takaoka & Choochote, both from Thailand, and Simulium (Asiosimulium) suchitrae Takaoka from Nepal.
Simulium (Simulium) kisapense sp. nov. is described on the basis of reared adult, pupal, and larval specimens collected from Langkawi Island, Peninsular Malaysia, and placed in the multi-striatum species-group in the subgenus Simulium. This new species is characterized by the bare basal section of the female radial vein, the male ventral plate with setae, the eight pupal gill filaments divergent at an angle of >90 degrees, and the shoe-shaped cocoon with small lateral window(s). Taxonomic notes are given to separate this new species from S. (S.) hirtinervis Edwards and S. (S.) malayense Takaoka and Davies, both from Peninsular Malaysia, and several other known species from Bhutan, India, Nepal, and Thailand.
Two new species of black flies, Simulium (Simulium) murudense and Simulium (Simulium) cheedhangi, are described on the basis of females, males, pupae, and larvae collected in Mount Murud, Sarawak, Malaysia. Both species belong to the Simulium melanopus Edwards species group. S. (S.) murudense sp. nov. is distinguished from most known species by a combination of the haired basal portion of the radial vein and the darkened fore coxae, and S. (S.) cheedhangi sp. nov. is characterized in the female by having a medium-sized claw tooth and in the pupa by six somewhat inflated gill filaments. Notes are given on the S. melanopus species-group in Sarawak and Sabah.
Simulium (Simulium) lomkaoense sp. nov. is described from females, males, pupae, and larvae in Thailand. This new species is assigned to the Simulium malyschevi Dorogostaisky, Rubtsov & Vlasenko species-group of the subgenus Simulium, and appears to be closely related to Simulium baimaii Kuvangkadilok & Takaoka from Thailand in having a similar shape of the female and male genitalia, pupal gill with two inflated filaments, and simple wall-pocket-shaped cocoon. This new species is compared taxonomically with S. baimaii and other related species. It represents the third species of the S. malyschevi species-group known from Thailand.
A new species of black fly, Simulium (Simulium) luculentum, is described from specimens collected in Thailand, and is assigned to the Simulium variegatum species-group of the subgenus Simulium Latreille. This new species is distinguished from most members of this species group in the female by the mid femur and tibia entirely yellowish; and in the pupa by the gill with six filaments, which are somewhat inflated basally. This species represents the fifth member of the S. variegatum species-group recorded from Thailand.
Simulium (Simulium) umphangense, a new human-biting species of black fly, is described based on females captured while attacking humans in western and central Thailand. The female of this new species is similar to those of S. (S.) indicum Becher, S. (S.) nigrogilvum Summers, and S. (S.) vanellum Huang et al. in the Simulium griseifrons species-group of the subgenus Simulium Latreille in having the frons densely covered with golden-yellow short hairs, a character rarely found in the subgenus Simulium. This new species is readily distinguished from the three related species by having a darkened fore tibia, a bare subcosta (or rarely with a few hairs), and an ovipositor valve not protruded posteriorly. Additional diagnostic characters of this new species are noted. This is the seventh human-biting species of black fly in Thailand.
Two new species of black flies, Simulium (Simulium) srisukai and S. (S.) kiewmaepanense, are described from specimens collected in Thailand. Both species are assigned to the Simulium variegatum species-group of the subgenus Simulium (Simulium) Latreille. They are characterized by the darkened female femora and tibiae and six inflated pupal gill filaments, and the darkened female tibiae and six ordinary thread-like pupal gill filaments, respectively. Taxonomic notes are given to separate these new species from 10 related species among the group. These new species represent the third and fourth species of the S. variegatum species-group from Thailand.
The classification, annotated list and keys for the black fly species from Peninsular Malaysia are updated. The number of black fly species increased from 38 in 1995 to 62 (including a new species herein described) in 2018. The 62 species are classified in four subgenera of the genus Simulium: one species in Daviesellum, 35 species in Gomphostilbia, five species in Nevermannia and 21 species in Simulium. Species in the latter three subgenera are further placed in species-groups or subgroups. Keys are provided for females, males, pupae and mature larvae. Simulium (S.) perakense sp. nov. is described and placed in the S. striatum species-group. The males of S. (G.) decuplum, S. (G.) tahanense, S. (S.) malayense, the female of S. (G.) adleri, and the female and larva of S. (G.) varicorne are described for the first time. The female, male, pupa and larva of S. (G.) trangense, the male and pupa of S. (G.) varicorne and the pupa of S. (G.) adleri are redescribed. Simulium (G.) sp. A is identified as S. (G.) pegalanense. Brief notes for each species are given on morphological characteristics, aquatic habitats and geographical distributions.