Effects of low temperature on the condition of flight muscles and flight propensity in a water strider, Aquarius paludum (Heteroptera: Gerridae)

Effects of chilling on dispersal characteristics of adults of the water strider, Aquarius paludum were studied in the laboratory. The condition of flight muscles was monitored during overwintering under natural conditions in Kochi (33degreesN), Japan. For diapause adults kept under 12h light-12h dark (12L:12D), chilling at 7degreesC for 48h from the 70th day after emergence caused lower Supercooling Point (SCP) and promoted higher flight propensity than among gerrids not exposed to chilling. For reproductive adults kept under 15.5L:8.5D, 91.3% of 34 adults retained well-developed flight muscles 1 week after the chilling (49 days after emergence), whereas 67.6% of 49 adults which had not been exposed to 7degreesC histolysed their flight muscles. According to diapause development, part of the adults which had well developed flight muscles histolysed them during December to February. Chilling in fall might trigger dispersal to overwintering sites by diapause adults and, that in spring could inhibit histolysis of flight muscles by over-wintered reproductive adults.