Host Acceptance

Although perhaps not technically part of host-seeking behavior, whether a host can be recognized as such after it has been contacted by a parasitoid is very important for the parasitoid. If a female cannot recognize a host as suitable for her progeny, habitat and host-finding activities would be wasted. Parasitoids have evolved behaviors that enable them to accurately choose suitable hosts. Many detect chemicals in the host cuticle or egg chorion that enable them to differentiate one potential host from another. These they usually detect with their antennae (Hymenoptera) or front tarsi (tachinid flies). Some parasitoids are also able to distinguish between hosts after insertion of the ovipositor by use of sense organs on the egg-laying organ itself. Acceptance of hosts via other sensory modalities, such as touch, sound, or sight, have also been documented. For instance, a Trichogramma wasp female examines a host egg with her antennae to determine its size. The ichneumonid parasitoid Campoletis sonorensis is influenced by host caterpillar shape. A cylindrical shape that approximated the shape of the Heliothis virescens host was more effective in stimulating oviposition than round or flat shapes. The egg—larval parasitoid Chelonus texanus accepts host lepi-dopteran eggs that have a rough or sculptured surface rather than a smooth one. Hairs from the body of gypsy moth larvae are enough to cause examination behavior in the parasitoid C. melanoscela. Movements perceived by sight or through vibrations of the substrate are important cues for a number of different parasitoids.

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