Effect of parental age and developmental rate on the production of active form of Callosobruchus maculatus (F.) (Coleoptera: Bruchidae).

Three similar experiments were conducted to see the effect of parental age and parental developmental speed on the production of "active-form" (i.e., capable of flight) offspring in Callosobruchus maculatus (F.). In experiment I, using the adults which emerged on three different days (as fast, intermediate, and slow in development), eggs were collected on three different days (at young, middle, and old age) during the adult life span. The results showed that the older parents produced more active-form offspring irrespective of the parents' own rate of development. In experiment II, the parental rate of development was investigated in more detail by using the adults that emerged over the entire span of their emergence period. In experiment III, the effect of parental age was investigated in more detail by collecting the eggs daily during the female adult's entire life span. Both experiments confirmed the trend observed in experiment I. From these results it can be concluded that the older the parents, the higher the percentage of the active form in their offspring. However, there was no significant systematic trend due to the length of the developmental period of the parents as seen in the parental age. This trend, that more active forms emerge from older parents, seems to be related to the decreased viability of older parents. It is thought that the less viable eggs produced by older parents are more susceptible to stimuli which induce the active form.