THE ALLOMETRY OF EGG SIZE AND NUMBER IN INSECTS

I describe the interspecific scaling of egg size, egg number, and ovary volume in three insect orders; Diptera, Hymenoptera, and Coleoptera. Egg number is correlated with body size in Diptera but not in the Hymenoptera or Coleoptera, whereas egg size and ovary volume are correlated with body size in all three orders. Egg volume shows strong negative allometry in all three taxa whereas ovary volume scales isometrically in the Diptera and Hymenoptera and with negative allometry in the Coleoptera. In all three orders there was a strong negative correlation between the residual values of egg size and number from plots of these parameters versus body size. This is evidence that there is a tradeoff between egg size and number. I argue that the proximate cause of the isometric or negatively allometric scaling of ovary volume and body size is to maintain functionally equivalent levels of locomotor performance. These results are also similar to the results of arguments based on the analysis of direct measurements of energy intake and energy required for maintenance.