Studies on the Self-regulation of Life Cycle in Anomala cuprea HOPE (Coleoptera : Scarabaeidae). : III. The Effects of Larval Density and Delayed Hatching on the Life Cycle

Abstract

The effects of larval density and delayed hatching on the life cycle of Anomala cuprea were investigated under field conditions and the vertical distribution of larvae was examined in relation to the soil temperature. The mean developmental velocity tended to diminish with the increase of larval density. After hibernation the population was separated into two groups, one emerged as adults from June to July and the other in the following June. When larvae hatched from eggs in mid September they remained in the first instar or developed only to the second instar before hibernation. The first instar larvae suffered from high mortality during hibernation. The individuals that had survived hibernation entered diapause in the summer and pupated the following year. The period of adult emergence in all the experimental populations was the same as in the natural population.The vertical distribution of larvae in the soil changes seasonally. They stayed near the surface from summer to autumn and burrowed deeper in winter. The larvae with a yellowish body colour stayed in deeper sites except from spring to early summer. The significance of this variation in distribution is discussed. From these results it was concluded that the life cycle of this species was regulated to synchronize the seasonal occurrence of adult emergence.