Egg production and oviposition pattern in the long- and short-winged females of water strider, aquarius paludum

Abstract

The Japanese water strider, Aquarius paludum(Fabricius), exhibits wing dimorphism: long- and shortwinged adults. In order to clarify the reproductive strategy in each morph, changes in the number of eggs in the nonsexual period were examined by dissection. Immediately after emergence, a few immature eggs were found in the ovaries of females in both morphs. The number of immature eggs increased with age, and a maximum of 50 eggs had accumulated in 5-day-old females of each morph. Submature eggs were found in 3-day-old long-winged females, but in 1-day-old short-winged females. Additionally, mature eggs appeared at 5 days of age in long-winged females, later than in short-winged ones. Although the number of mature eggs increased with age, by 13 days, the maximum number of mature eggs in long-winged females was lower than that in short-winged ones. Females younger than 11 days of age showed mate refusal behavior. Females began to oviposit 2 days after copulation. The size of the first clutch of longwinged females was significantly smaller than that of short-winged ones. However, after the fourth clutch, there were no significant differences in clutch size between the two morphs. Therefore, more eggs produced by short-winged females were found during the pre-reproductive period.