Intraspecific Variation in Body Size and Fecundity in Insects: A General Relationship

The relationship between intra-specific variation in female body size and potential fecundity was investigated using the published literature on 57 oviparous species of Coleoptera, Diptera, Ephemeroptera, Heteroptera, Homoptera, Hymenoptera, Lepidoptera, and Trichoptera, and 11 species of larviparous Aphidina and Diptera. Female body sizes were converted to dry body weight. Variation in body weight and fecundity was expressed as percentage deviation from the median values. The increase in fecundity with body weight was similar in most taxa, with only a few important exceptions. The common regression for oviparous and larviparous species predicts a 0.95% increase in median fecundity for each 1% increase in dry body weight. The number of ovarioles (in 10 species of Coleoptera, Diptera, Hymenoptera and Orthoptera) also increased with body weight. The general relationship predicted a 0.81% increase in ovariole number for each 1% increase in dry body weight. The slope of ovariole number versus weight relationship was greater in species with many ovarioles than in species with few. The common slope of the fecundity/size relationship is close to 1 and this indicates that female size is a principal constraint on insect potential fecundity.