Number of annual generations of cletus punctiger(heteroptera: Coreidae) estimated using developmental zeros and effective accumulative temperatures of individuals carrying symbiotic bacteria

Abstract

Cletus punctigerDallasHeteroptera: Coreidaeis widely distributed in Japan. This insect is a serious pest that sucks developing rice kernels and causes pecky rice. Adults collected in environmental fields, orally acquire symbiotic bacteria belonging to the genus Burkholderia from environmental soil in the nymphal stage and commonly possess the symbionts in their gut crypts. Therefore, we examined whether nymphs reared with food, water and soil collected from their natural habitat acquire the symbionts. Rearing experiments with soil demonstrated that nymphs acquire the symbionts. We then investigated the developmental zeros and effective accumulative temperatures using rearing experiments with food, water, and soil. The developmental zeros were 14.3°C in the egg stage, and 14.0°C and 14.1 °C from the egg to the nymph stage in the females and males, respectively, and 12.8°C in the preoviposition period. The effective accumulative temperatures were 84.0 day-degrees in the egg stage, 344.8 day-degrees from the egg to the nymph stage in both females and males, and 131.6 day-degrees in the preoviposition period. Based on the data above, the number of annual generations of C. punctiger in Shiga Prefecture was estimated to be three at the most. The new adults in the third generation are considered diapause adults that move to hibernating sites.