Light trap catches of blackflies in southern part of Kyushu, Japan

Abstract

Using light trap (black light), night catches of some Japanese black flies were made in southern part of Kyushu, Japan, during the years 1975-1977. Light traps were set and operated weekly or daily for varying periods at different places : A-cowshed in mountainous area, E-dwelling house in a sparsely populated district in the city, both places being 2km from the nearest breeding sites, B-cowshed in a pasture infested with bovine Onchocerciasis in a mountainous area, C-pigsty in a rural area, and D-poultry farm in the suburbs of the city, where two to six species of simuliids were found breeding in streams within 500m from the trapping sites. In the cowshed (A), of which the structure of the wall prevented the light of trap from escaping outwards, a total of 268 females belonging to 6 species were collected during three years from 1975-1977. The 268 females included 143 Simulium (Simulium) japonicum, 57 S. (Odagmia) aokii, 29 S. (S.) arakawae, 21 S. (S.) rufibasis, 15 S. (Gnus) bidentatum and 3 S. (S.) quinquestriatum. All species contained blood-fed females in different ratios from 23.8 to 46.7% of the total, but neither gravid female nor male individual. In another cowshed (B), which was roughly built, lacking walls on south and north sides, thus permitted the light of the trap to extend outwards to a considerable distance from the cowshed, a total of 108 adults were captured by 10 trappings from June to September 1977. Species and the number of flies trapped were S. (S.) japonicum 84,S. (S.) arakawae 11,S. (Eusimulium) uchidai 5,S. (G.) bidentatum 4,S. (S.) rufibasis 3 and S. (S.) quinquestriatum 1. Of these, 10 S. (S.) japonicum, 2 S. (S.) arakawae, 2 S. (G.) bidentatum and 1 S. (E.) uchidai were males. And, of 93 females captured, 22-100% of blood-fed females were found in S. (S.) japonicum, S. (S.) arakawae, S. (S.) rufibasis and S. (G.) bidentatum, and 23-100% of gravid females in all species except for S. (G.) bidentatum. In the pigsty (C), 10 trappings between February and June 1975,yielded 10 black flies consisting of 3 S. (E.) uchidai, 2 S. (E.) aureohirtum, 2 S. (S.) arakawae, 1 S. (G.) bidentatum, 1 S. (S.) japonicum and 1 S. (S.) nikkoense. Two of these were male individuals, belonging one to S. (E.) uchidai and one to S. (G.) bidentatum. One of 2 S. (S.) arakawae was engorged with blood. A single blood-fed female of S. (E.) uchidai was trapped in the poultry (C) by 34 weekly night collections from April to October 1977,and also one unfed female of S. (S.) arakawae in the dwelling house (E) by 115 light trappings from September 1976 to August 1977. From these results, some ecological aspects of adult black flies in southern part of Kyushu were revealed as follows : 1) Females of S. (O.) aokii, S. (G.) bidentatum, S. (S.) arakawae, S. (S.) japonicum, S. (S.) rufibasis and S. (S.) quinquestriatum fly to the cowshed at least 2km from their breeding sites, presumably feed on cattle, even at night and then fly away sooner or later before they become gravid. 2) A light trap operated near breeding places captured males as well as females of the same species as found by the previous collections of the immature stages, suggesting that flight range of male individuals of some black flies is confined to the area not far from their habitats. 3) The seasonal span of both S. (S.) japonicum and S. (S.) arakawae in the trap in the cowshed (A) was from the middle of May to the beginning of November and that of S. (O.) aokii and S. (S.) rufibasis from the middle of May to the late of August. 4) A marked decrease in the number of females per night trapped in the cowshed (A) between 1975 and 1977 was considered mainly due to the construction work of the new highway which destroyed many breeding places for the aquatic stage of black flies. 5) S. (S.) japonicum was supposed to be a vector of Onchocerca gutturosa, a parasite of bovine Onchocerciasis prevailing in the pasture (B).