Avoidance of superparasitism: a matter of learning?

Superparasitism (laying eggs into parasitized hosts) by solitary parasitoids was regarded for a long time as a mistake on the part of the foraging parasitoid, but is now widely accepted as often adaptive. In Venturia canescens the rate of avoidance of superparasitism has been shown to rise over the first 20 min from the deposition of the first egg, possibly because of a constraint in the detectability of the marker used to label parasitized hosts. Here, we show that the increase in avoidance of superparasitism with time is the result of a female's experience of hosts in the interval between laying an egg in a host and re-encountering that same host. Wasps deprived of hosts in this interval showed no avoidance of superparasitism; those given healthy hosts every 3 min during this interval showed increasing avoidance of superparasitism with time. Furthermore, the marker was detectable in a host within 3 min of oviposition. The results suggest that wasps quickly acquire information about the abundance of healthy hosts in their environment, and base their decision to superparasitize on this information. Copyright 1999 The Association for the Study of Animal Behaviour.