1. The ovigeny index, previously identified as both a significant fitness variable in parasitoid wasps and an important factor in parasitoid–host population dynamics, is the proportion of the maximum potential lifetime complement of eggs that is mature when the female emerges into the environment following pupal development. We tested the hypothesis that ovigeny index varies with female body size in parasitoid wasps. Body size measurements were obtained for 40 species in 13 families, representing a broad taxonomic and morphological diversity of parasitoid wasps. There was an almost 18-fold difference in size between the smallest and the largest species.
2. Ovigeny index is shown to be negatively correlated with body size across species – smaller wasps have a higher proportion of eggs mature at emergence than do larger wasps – a result supporting the hypothesis. This relationship has previously been observed within species.
3. The previously reported cross-species negative correlation between life-span and ovigeny index is robust, as it still holds when variation in body size is controlled for.
4. We discuss the likely selective factors in the evolution of a link between ovigeny index and body size across species.