The Inheritance of an Acquired Taste: Learning and Passing on New Food Odor Preferences in Butterflies

The larvae of butterfly and moth species are often specialist herbivores that feed on very specific plant hosts. However, as a group, they feed on a large diversity of plants. We wondered how diet diversification evolves, i.e., how a specialist acquires the ability and preference to feed on a novel host. We hypothesized that oviposition mistakes may lead larvae to acquire a taste for the novel host, and perhaps even pass on this learned preference to its offspring, facilitating host switches. This chapter details a series of experiments that show this to be the case with larvae of Bicyclus anynana butterflies that learn to feed on plant leaves with a novel artificial odor. We also show that the hemolymph of the larvae carries factors that help in the transmission of the learned preference to recipients and to their offspring. Finally, we show that a few genes are differentially expressed in brains of larvae that feed on leaves with and without the odor, but the messenger RNA of these genes are not the epigenetic factors that are inherited by the offspring.