Variations In Hostseeking Behavior

Although the host-seeking process in parasitoids may be very efficient, such that eggs are deposited only in host species suitable for their development, other strategies are used. Some parasitoids lay eggs in an area likely to be inhabited by their host. The larvae hatching from these eggs then must find their own way to the host. Members of the hymenopteran family Eucharidae are parasitic on ant larvae. Adult females lay eggs on or in plants. Each hatching larva is a planidium and so is free living and waits until it can attach to a passing adult ant, whereby it is taken into the nest and transfers to ant larvae. Many immature blister beetles (family Meloidae) are also parasitoids. Adult females lay eggs in the soil or sometimes on plants, and the emerging larvae are called triungulins. These active larvae find their own way to the eggs of locusts or nests of solitary bees, where they devour the eggs and/or provisions of the hosts. (Strictly speaking, meloids should probably be called "egg predators"; but their impact is much like that of true parasitoids.) Some tachinid flies lay large numbers of very small eggs on foliage that potential hosts may eat. In some cases, the females are attracted to damaged leaves, and this increases the chances of success for their larvae, but suitable hosts may never ingest many eggs. Nevertheless, these parasitoids may be as host specific as those that actively search for hosts.

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