August 11th, 2022

Harvester Butterfly (Feniseca tarquinius)

The harvester butterfly is a small, uncommon species found most often in swampy areas and woodlands, native to the east coast of North America. This species is highly localized, preferring to remain close to wooly aphid colonies, often in the periphery of alder trees.

This dainty yellow butterfly is unique in the fact that it is the only carnivorous butterfly species in North America. To be more precise, its larval form is insectivorous; it feeds on the flesh of wooly aphids, which are tiny, sap-sucking insects of the sub-family Eriosomatinae. Unlike most other butterflies, adults do not feed on nectar; they are instead known to feed on the honeydew of aphids, as well as sap, dung and mud. Single eggs are laid on leaves near wooly aphid colonies, and thanks to a high-protein diet, larvae develop very quickly. Due to this rapid life cycle, harvester butterflies can produce up to six generations per year!

There is an important obstacle in the path of the harvester caterpillar's goal of stuffing itself with an aphid buffet, however: ants. Many ant species are known to protect and tend to their own aphid colonies with the goal of collecting the honeydew they produce, which these ants feed on. In order to infiltrate the colony without rousing the ants' suspicions, the caterpillars use a clever disguise: they attach half-eaten aphid carcasses to themselves to conceal their presence from the ant protectors. These caterpillars have the capacity to imitate aphids' chemical signature, called a cuticular hydrocarbon profile; these are individual-specific signaling molecules produced by the epicuticle of certain insects, used primarily for identification between members of a species.