Abstract
Observations were conducted on the seasonal incidence of biting midges, which flew into light traps in the barns of this laboratory, and on the nematodes were detected from their bodies, from June 1954 to July 1955, at Kodaira, in the suburb of Tokyo. Seven species of Culicoides were collected. Of these, C. sigaensis, C. oxystoma and C. arakawae are known but C. odibilis is unknown in Japan, and the rest were new species. The new species will be described in the near future by Dr. M. Tokunaga as C. nipponense (C. sp. II) and C. kitaokai (C. sp. III). The prevalence of these species are shown in Table 1 and Table 2. In 1954, C. sigaensis was exceedingly dominant, C. oxystoma, C. arakawae were next in numbers and other species were rare. In 1955, the constitution of the species populations differed from that of the preceding year and C. oxystoma was the most dominant in August and C. sp. II was common. Engorgement of these biting midges was observed only in C. sigaensis, C. oxystoma, and C. sp. II. A parallelism between the percentage of blood sucking of the biting midges and the number collected was not noticed, but a correlation between the ratios of blood sucking of C. sigaensis and C. oxystoma was significant. A microfilaria-like nematode (0.31%) was found in the engorged C. sigaensis, but two types of nematode (2.2%) were found in a larger percentage from the non-sucking ones. The microfilaria-like nematode may be the microfilaria of Onchocerca cervicalis, but further studies and observations will be necessary to make any conclusion. The writers would regard C. sigaensis as an unsuitable intermediate host for O. cervicalis based on these results.
