The Significance of the Environment in the Control of Insect Fecundity

Abstract

P. W. Frank, in 1965 Encyclopedia Britannica, defines fecundity as the power to produce functional gametes; commonly only female gametes are considered as ascertaining fecundity. Fecundity is, in essence, a production rate that increases with each succeeding Two fundamental aspects become obvious. Fecundity is a process of species multiplication, and it is related to formation of female gametes. Thus, fecundity is an essential element in evolution of populations: it increases population size with each generation. As this number gets reduced by selective factors in course of biological cycle, it allows new genic combinations to occur, through meiosis and amphimixis. However, female gametes must carry out a third function. Since offspring cannot reach their functional autonomy without minimum organo­ genesis, oocytes must contain not only cellular components but also materials indispensable to this histogenesis and organogenesis. In addition, because of gamete dimorphism, ovule of insects is not mobile, and so distribution of female gametes, and consequently of zygotes, must necessarily correspond to that of de­ scendants at birth; therefore way eggs or viviparous larvae are distributed by female is an essential element for survival of species. Thus, fecundity is not merely production of a number of female gametes. This aspect cannot be dissociated from adaptations allowing best utilization of gamete production to ensure genetic recombination and survival of descent. In an environment heterogenous in space and time, not one of these characteris­ tics of insect fecundity can occur independently of ecological constraints; each one