Seasonal and Diurnal Changes in Emergence of Potamanthodes kamonis in a Stream of Central Japan (Ephemeroptera : Potamanthidae)

Abstract

Seasonal and diurnal changes in emergence of P. kamonis were studied using a light trap and emergence traps in a stream of central Japan in 1978-1980. The main emergence period was from mid-July to the end of September. Most of the winged adults collected were subimagos. Subimagos gradually decreased in size during the emergence periods in 1979 and 1980, but this tendency was not so clear in 1978. The emergence continued from sunset to sunrise each day in the middle of the emergence period, but it ceased far earlier before sunrise on the early and later days of the period. The daily emergence time of females was somewhat earlier than that of males, and the proportion of males to females gradually increased toward sunrise.