Large body size enables front-loaded reproductive effort in Coleomegilla maculata

Food availability during insect development can have legacy effects on adult reproductive performance. In lady beetles, female body size can vary greatly depending on the environmental conditions and food resources encountered during development, but it is not yet understood how body size may influence the trade-off between offspring size and number. We followed the reproduction of Coleomegilla maculata females that developed under different levels of resource availability. Larvae were provided daily access to food (eggs of Ephestia kuehniella) for either 30 minutes, six hours, or ad libitum. Mated adult females were then fed ad libitum on the same food and their oviposition (clutch size, egg size and egg fertility) was monitored daily throughout their lives. The treatments produced three developmental rates (slow, medium, fast) and corresponding differences in body size (small, medium and large). There was no effect of treatment on mean egg size, but egg size gradually increased over the the first 20 clutches. Small females laid fewer eggs over their lifetime than did large females, indicating that they maintained a minimum egg size at the cost of reduced fecundity. The clutch size of small and medium sized females increased over the course of the first 60 clutches, whereas that of large females declined. Thus large females ‘front-loaded’ their reproductive effort by producing a larger proportion of their progeny early in adult life when egg fertility was highest. The adaptive significance of these results are discussed in the context of life history evolution and the aphidophagous lifestyle.