[Sexual dimorphism in photoperiodical plasticity of body mass in the green dock leaf beetle Gastrophysa viridula].

Sexual dimorphism in body mass was studied in prepupae, pupae and immature adults of the green dock leaf beetle Gastrophysa viridula under a constant temperature of 24 degreesC and two photoperiods (12L: 12D and 22L:22D). Females were significantly heavier compared to males at all the three developmental stages; just after emergence from pupae they weighed on average 11.4 mg while males -10.3 mg. Sex differences in photoperiodic body mass plasticity were revealed: under short-day conditions pupal and adult mass in females was significantly higher compared to long day, but not in males. Such a response to short day (the factor inducing reproductive diapause in this species) is likely to promote accumulation of greater amount of nutrients by females which is necessary for earlier oviposition after over-wintering.