Suspending cocoons to evade ant predation in Meteorus pulchricornis, a braconid parasitoid of exposed-living lepidopteran larvae

We tested the hypothesis that cocoon suspension by a thread in hymenopteran parasitoids is a defense tactic against predators, by comparing predation against suspended and non-suspended cocoons of the braconid wasp Meteorus pulchricornis on a Quercus phillyraeoides hedge on which workers of the common small ant Crematogaster matsumurai were foraging. The lost proportion of non-suspended cocoons, which were artificially attached to leaves of Q. phillyraeoides, markedly decreased with cocoon age, indicating a critical phase of predation on young cocoons. No suspended cocoons at age 1-12 h at the beginning of exposure were lost within 12 h, whereas more than 75% of same-aged non-suspended cocoons were lost in the same period. Predation against such young cocoons would be a strong force driving the evolution of cocoon suspension in parasitoids of exposed-living host insects.