Parasitic wasps as sleuthhounds. Response of an ichneumon wasp to the trail of its host.
1981
Klomp H.
Experiments have been performed showing that the ichneumon wasp Poecilostictus cothurnatus, a parasitoid of the advanced larvae of the pine looper, Bupalus piniarius, is able to locate the host by following the trail left on the needles by the crawling caterpillars. Artificial trails can be prepared by moving the skin of a caterpillar over a sheet of paper, showing that one or more chemicals present in the cuticular layer function as signals (kairomone) for the wasp. When no caterpillar is found when she arrives at the end of the trail, the wasp shows a characteristic behaviour known as area-restricted searching. This type of behaviour has been found in several other species of parasitoids, but in all these cases it was performed immediately after having parasitized a host. The observations suggest that in a pine forest host finding is accomplished by alternating short flights with landings on twigs. After a landing there is a short search for the presence of a trail, and, coming across one, the wasp will try to find the host. If th is is found and parasitized she flies away, and will probably soon make a new landing elsewhere.
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