Effects of constant temperatures on oviposition and immature development of Simulium bidentatum (Diptera: Simuliidae), a vector of bovine Onchocerca (Nematoda: Onchocercidae) in central Kyushu, Japan.

Laboratory developmental studies were carried out on Simulium bidentatum (Shiraki) under constant air and water temperatures (7, 10, 13, 16, 19, 22, 25, and 28 degrees C). The median time required for female flies to complete oocyte maturation after blood feeding decreased from 8 to 1.5 d and the median time from blood feeding to oviposition decreased from 16 to 3 d as air temperature increased from 7 to 28 degrees C. Air temperatures from 16 to 22 degrees C were most suitable for oviposition. An average of 61.4% of eggs hatched. Egg developmental period decreased from 17 to 4.5 d when water temperature increased from 7 to 19 degrees C and decreased to 3.5 d when water temperature was between 22 and 28 degrees C. Larval and pupal development occurred at water temperatures > or = 13 degrees C, but was most successful from 16 to 22 degrees C. Seven (in 16 lots) or 6 instars (in 1 lot) were indicated by using the Dyar rule. We conclude that S. bidentatum is adapted to moderate weather conditions in spring and autumn and that approximately 7 generations of this species occur per year in Oita, Japan.