1. The balance between risk and benefit of exploiting resources drives
life history evolution. Predators are naturally recognized as major
drivers of the life history evolution of their prey. The concept of an
evolutionary arms race posits that prey also influence the life history
evolution of their predators. There is far more evidence on the role of
predators than of prey. 2. The goal of this study was to investigate the
role of prey in life history evolution of predators using ladybird
beetle predators either of aphids or coccids. These particular organisms
were chosen because literature shows that the pace of life of aphids is
faster than that of coccids and this difference is reflected in the life
histories of the ladybirds that specialize on feeding on aphids or
coccids. 3. Thirty-four species of ladybird predators of aphids and
eight of coccids belonging to five different tribes were collected and
reared in the laboratory. The females were weighed as well as their
eggs, and their reproductive investment calculated as the number of
ovarioles multiplied by the average mass of an egg. Phylogenetic
relatedness was controlled for in the statistical analyses. 4.
Controlling for female mass revealed that ladybird predators of aphids
lay bigger eggs and have a higher reproductive investment than ladybird
predators of coccids. These differences are not influenced by
phylogenetic relatedness but only by the type of prey. We suggest that
ladybird predators of coccids lay smaller eggs because neonate larvae do
not have to search, catch and subdue prey, and that they have a smaller
reproductive investment because they need to allocate more resources to
locate prey. 5. Recognizing the influence of prey on the life history
evolution of predators is important for understanding food web dynamics.