Biological characteristics of a non-photoperiodic-diapause strain of the cabbage beetle Colaphellus bowringi (Coleoptera: Chrysomelidae)

Comparison of biological characteristics between diapausing and non-diapausing strains of insects provides some insights into the mechanisms regulating diapause. In this study, biological characteristics, especially diapause characteristics and life-history traits, of a non-photoperiodic-diapause (NPD) strain of the cabbage beetle Colaphellus bowringi were compared with those of a normal, high-diapause (HD) strain that enters diapause in response to either long day length or low temperature. The NPD strain did not enter diapause at any photoperiod at 22°C or higher, but still had a capacity to enter diapause at low temperatures. Although diapause could be induced in both strains by exposure to 20°C, the proportion of individuals having shorter diapause duration was greater in the NPD strain compared to the HD strain. The NPD strain had significantly lower hatching and larval survival rates, longer developmental duration of immature stages, smaller body size and lower longevity and female fecundity compared to the HD strain. The NPD strain of this species is a promising model for investigating diapause regulation in insects in general.