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Quantitative short-day photoperiodic response in larval development and its adaptive significance in an adult-overwintering cerambycid beetle, Phytoecia rufiventris

Shintani, Yoshinori
Journal of insect physiology 2011 v.57 no.7 pp. 1053-1059
Chrysanthemum, Coleoptera, adults, artificial diets, autumn, diapause, insect larvae, larval development, molting, overwintering, photoperiod, pupae, pupation, rearing, spring, summer, survival rate, winter
The chrysanthemum longicorn beetle, Phytoecia rufiventris, overwinters in the adult stage and reproduces in spring. Larvae of this beetle develop during summer inside a host stem or root. In the present study, photoperiodic control of larval development and its adaptive significance were examined in this beetle using an artificial diet. Larvae showed a short-day photoperiodic response at 25°C with a critical day length of around 14h; larvae reared under short-day conditions pupated, whereas those reared under long-day conditions entered summer diapause with some supernumerary molts and did not pupate. A similar response was found at 30°C, but with a shorter critical day length. Below the critical day length, a shorter day length corresponded to a shorter larval period. Larvae transferred from long-day conditions to various photoperiods showed a similar quantitative response. Field rearing of larvae starting at various times of year showed that pupation occurs within a relatively short period in early autumn. Field rearing of pupae and adults at various times indicated that only pupation in early autumn results in a high survival rate until winter. Earlier or later pupation led to a low survival rate due to death before overwintering in the adult and pupal stages, respectively. Thus, in P. rufiventris, timing of pupation regulated by the quantitative short-day photoperiodic response is vital for survival. Relatively lower developmental threshold in the pupal stage supports this hypothesis.