Seasonal microhabitat selection by an endoparasitoid through adaptive modification of host behavior.

Differences in the distribution of parasitized and unparasitized hosts has been used to infer modification of host behavior by insect parasitoids. Data are presented showing that not only do parasitized hosts behave differently from unparasitized ones, but that the behavior of parasitized hosts varies in function of the physiological state of the parasitoid. Aphids containing nondiapausing parasitoids leave the aphid colony and mummify on the upper surface of the leaves, whereas those containing diapausing parasitoids leave the host plant and mummify in concealed sites. Modification of host behavior by diapausing parasitoids results in the selection of a suitable microhabitat that reduces the incidence of hyperparasitism and should decrease the action of adverse climatic conditions during the lengthy dormant period.