Developmental biology and phenology of a Korean native dung beetle, Copris ochus (Motschulsky) (Coleoptera: Scarabaeidae)

This paper describes the development and life history of a Korean native dung beetle, Copris ochus (Motschulsky), based on laboratory studies of beetles collected from the subtropical island of Je-Ju. The species is brood-caring and has an annual life cycle. Females lay a single batch of eggs in late summer or early autumn. Larvae develop to the 3rd instar and enter diapause before the onset of winter. Diapause is terminated by low winter temperatures that also prevent pupation until spring. Parents and progeny emerge together in mid-summer and undergo a period of intensive feeding before oviposition in late summer or early autumn. Some adults are present early in May-June and may represent insects that overwintered without breeding, or adults that emerged early because of the premature death of their offspring. Males and females co-operate in construction a brood chamber that is provisioned with fresh dung for oviposition. The chamber is commonly formed at depths of 22-35 cm below the surface and may contain 2-5 brood balls. Brood balls are generally pear-shaped (4.1 ± 0.4 cm long and 3.8 ± 0.3 cm in diameter), and each contains a single egg. Females lay an average of one egg for every 45 ml of dung buried (n = 26). At 25°C, the duration of embryonic development is 9.0 ± 1.7 days, followed by 6.1 ± 1.0 and 7.8 ± 1.9 days for the 1st and 2nd larval instars respectively. The duration of the third instar was indeterminate because this is the stage at which larvae enter diapause. This state of arrested growth persists over winter but development resumes in spring as temperatures begin to rise. In the laboratory, larvae were able to pupate at 25°C but only after they were exposed to a period of chilling, the optimum conditions for diapause termination being 30 days at 7.5°C. Under this combination of low and high temperatures, egg to adult development was completed in 26 weeks.