Oviposition habits of Simulium kawamurae (Diptera: Simuliidae), with reference to seasonal changes in body size and fecundity.

Oviposition habits and seasonal changes in wing length, head width, and number of ovarioles of Simulium kawamurae Matsumura were investigated in Kyushu Island, Japan. Gravid flies swarmed over turbulent water and laid eggs on rock surfaces in the splash zone. Large, irregular egg masses often resulted from the mass oviposition by many females within the same small area. Oviposition occurred at dusk during spring-summer, shifting to earlier periods during autumn-winter. Fecundity increased linearly as a function of body size (i.e., both with the cube of wing length and of head width, showing a better fit with the latter). Spring flies had a larger mean body size and fecundity than both summer and autumn flies. Winter flies had wings as long as spring flies, but their head widths and fecundity were comparable to summer-autumn individuals. This indicated seasonal variation in the relative proportion of body structures.