Damselfly
larvae
are found in ponds with minnows, and both species are consumed by pike.
Mealworms are not a natural prey for the pike but can be experimentally added
to its diet.
The larvae are exposed to water from a pike that had eaten
mealworms (A), minnows (B), or damselflies (C);
groups B and C responded by decreasing foraging behavior (feed on brine shrimp), but not group A.
Then the larvae are exposed to water from a pike that had been fed mealworms.
Groups B and C now have learned, based on experience from the first exposure,
to associate pike plus any scent (including that of mealworms) with danger,
and this translated into a reduced foraging rate.