Photoperiodic induction of larval diapause and temperature‐dependent termination in a wild multivoltine bruchid, Kytorhinus sharpianus

A wild bean weevil, Kytorhinus sharpianus Bridwell (Coleoptera: Bruchidae), has a multivoltine life cycle and enters a hibernal larval diapause at the fourth instar under a short daylength (Shimada & Ishihara, 1991). Here, we investigated their diapause incidence under different photoperiods at 24 °C and 27 °C. The critical photoperiods for diapause induction were 14.5 h at 24 °C and 14 h at 27 °C. The stages susceptible to diapause‐inducing stimuli were estimated by transferring larvae of various instars from long days to short days and vice versa. Then we investigated the incidence of larval diapause. The sensitive stage was estimated to be from the third to early fourth instar. Though larval diapause, which was induced under a short daylength, was terminated only by increasing the daylength, the termination was more synchronized by an exposure to a low temperature followed by increasing temperature, irrespective of photoperiod.