Feeding conditions modify the photoperiodically induced dispersal of the water strider, Aquarius paludum (Heteroptera: Gerridae)

Abstract

Overwintering adults of the water strider, Aquarius paludum were collected from the field in fall and kept under short days (12L : 12D) at 20°C for a week. A control group was then kept at 12L : 12D and fed daily, and three experimental groups were transferred to 15.5L : 8.5D and fed at different frequencies: daily or every 2nd or 3rd day. Temperature was kept at 20°C. Flight behaviour of the adults in the four groups was recorded every 10 days up to the end of the 5th week when the adults were dissected. State of the flight muscles and reproductive organs (ovaries and testes) was recorded. Flight ability of the adults fed every 3rd day (Group 3) was higher than that of those fed daily (Group 1). Seventy percent of the females that were fed every 3rd day (Group 3) remained in diapause for 5 weeks, in spite of the reproduction promoting long-days, while none of the females fed every day remained in diapause (Group 1). Flight muscle histolysis, promoted by long-days, was inhibited by poor feeding conditions. Thus, they can migrate and seek more suitable water bodies rich in food. The modifying effect of the availability of food on the trade-off between reproduction and flight is recorded here for the first time for a carnivorous insect.