Diapause development and photoperiodic activation in starving females of Pyrrhocoris apterus (Heteroptera)

Abstract

Diapausing adults of Pyrrhocoris apterus 3–9 weeks old were exposed for 1–10 weeks to combinations of photoperiod (18L:6D; 12L:12D) and temperature (26°C, 15°C) under starvation. Their response was then measured by the incidence of oviposition and duration of oviposition delay after a switch to 18L:6D, 26°C and feeding. Since vitellogenesis is prevented in starving females, diapause completion was reliably separated from post-diapause morphogenesis. Tachytelic processes of photoperiodic activation did not require feeding, but high temperature was essential; at 15°C and 18L:6D only horotelic completion of diapause (i.e. diapause development) was possible, similarly to 12L:12D and 26°C or 15°C. Tachytelic processes were even stimulated by starvation. Starvation did not increase the rate of horotelic processes. Tachytelic completion of diapause did not result in the loss of photoperiodic response. The involvement of changes in the photoperiodic clock in the horotelic and tachytelic processes is discussed.