Effects of thermoperiods on diapause induction in the cabbage beetle, Colaphellus bowringi (Coleoptera: Chrysomelidae)

Abstract

The effects of thermoperiods on diapause induction in continuous darkness or under a 12 : 12 h LD photoperiod were investigated in the cabbage beetle, Colaphellus bowringi Baly, a typical short-day species. The diapause response curves both at different constant temperatures and at the thermocycle of format CT x: (24 À x) h (16 : 28 C) under continuously dark rearing conditions showed that the incidence of diapause depended mainly on whether or not the mean temperature was 20 C or >20 C. If the mean temperature was 20 C, all individuals entered diapause; if >20 C, the incidence of diapause declined gradually with increasing mean temperatures. The thermocycle (CT 12 : 12 h) with a series of different cryophases (8-22 C) and thermophases (24-32 C) under continuous darkness demonstrated a cryophase response threshold temperature of approximately 19 C and a thermophase response threshold temperature of approximately 31 C. Thermoperiodic amplitude (temperature difference between cryophase and thermophase) was shown to have a significant influence on diapause induction at the mean temperatures of 22, 23 and 24 C, but not at !25 C. Thermoperiodic responses under LD 12 : 12 h clearly showed that the incidence of diapause was influenced strongly by the photophase temperature. The thermoperiod under LD 12 : 12 h induced a much lower incidence of diapause than the thermoperiod with the same temperature in continuous darkness. The ecological significance of thermoperiodic induction of diapause in this species is discussed.

Thermoperiodic response and effect of photoperiod on thermoperiodic induction of diapause in Colaphellus bowringi

“…Thermal response curves of C. bowringi for diapause induction were determined at 12, 16, 24, 28, and 30 °C under DD and LL (Figure 1) for comparison with previous results (Wang et al., 2004b). The response curves showed that temperatures per se could induce diapause in the absence of photoperiodic signals as well as under LL.…”

“… Thermal response curves for the induction of diapause in the cabbage beetle, Colaphellus bowringi at various constant temperatures under continuous darkness [n = 108–212, after Wang et al. (2004b)] and continuous light (n = 111–183).…”

“…The scotophase was controlled manually by enclosing the rearing boxes in opaque hoods. The supplies of food under continuous dark‐rearing conditions were made in a darkroom with red light and were completed within about 3 min for each box (Wang et al., 2004b).…”

“…The diapause‐averting influences of short day were expressed only at temperatures above 20 °C (Xue et al., 2002b; Wang et al., 2004a). We have recently shown the effects of thermoperiod on diapause induction under DD or under an L12:D12 photoperiod in this beetle (Wang et al., 2004b). According to our studies, the thermoperiodic effect on diapause induction depended on whether or not the mean temperature was below or equal to 20 °C.…”

“…(1976) for the southwestern cornborer, Diatraea grandiosella ; Dumortier & Brunnarius (1981) for the large cabbage white butterfly, Pieris brassicae ; Masaki & Kikukawa (1981) for the Indian meal moth, Plodia interpunctella ; Brown & Phillips (1991) for the braconid wasp, Microplitis croceipes ; van Houten et al. (1988) for the predatory mite, Amblyseius potentillae ; Fantinou & Kagkou (2000) for the Mediterranean corn stalk borer, Sesamia nonagrioides ; and Wang et al. (2004b) for the cabbage beetle, Colaphellus bowringi Baly (Coleoptera: Chrysomelidae).…”