Avoidance of superparasitism: a matter of learning?

Superparasitism (laying eggs into parasitized hosts) by solitary parasitoid s was regarded for a longtime as a mistake on the part of the foraging para sitoid, but is now widely accepted as often adaptive. In Venturia canescens the rate of avoidance of superparasitism has been shown to rise over the f irst 20 min from the deposition of the first egg, possibly because of a con straint 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 lay ing 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 h ost within 3 min of oviposition. The results suggest that wasps quickly acq uire information about the abundance of healthy hosts in their environment, and base their decision to superparasitize on this information. (C) 1999 T he Association fbr the Study of Animal Behaviour.