Found in swampy areas and woodlands, particularly near water, from southern Canada south to central Florida and central Texas. Highly localized with adults generally remaining in close proximity to woolly aphid hosts.

Larvae: The larvae are small (to 1.9 cm in length) and slug-like, brightly patterned with gray, yellow and white, and covered with bristly hairs; the pattern is often obscured with the white wax produced by the prey (Minno et al 2005).

Figure 3. First instar larva of the harvester butterfly, Feniseca tarquinius (Fabricius), full of woolly maple aphid blood. Photograph by Jerry F. Butler, Entomology and Nematology Department, University of Florida.

There are two to three generations in Canada and the northern U.S. and from three to six generations in the southern U.S.. Eggs are laid singly on leaves or stems near colonies of the woolly aphid prey. Caterpillars are present from June in the North and from February through early November in Florida.

Overwintering is by the pupal (chrysalis) stage (Allen 1997).

Because the harvester caterpillar is carnivorous, development proceeds very rapidly, with the larval stage being completed in as little as eight days. Harvester larvae have only four larval instars. Most other butterflies have five (Layberry et al. 2002). First instar larvae may restrain their larger aphid prey with silk prior to attacking them (Hall, unpublished observations).

Some harvester caterpillars cover themselves with the remains of woolly aphids they have eaten. The carcasses are tied on with silk, perhaps to protect the caterpillars from predacious ants (that tend and protect the aphids) and other natural enemies. Harvester caterpillars are less likely to conceal themselves when their woolly aphid prey is tended by Camponotus and Formica ants (Youngsteadt and Devries 2005).

Lohman et al. (2006) reported that the caterpillars share part of the cuticular hydrocarbon profile of the aphids and may be protected from the aphid–attending ants and protected by the ants from other predators by this chemical mimicry. Although harvester larvae lack the secretory and call-production organs of other ant-attended lycaenids (Youngsteadt and Devries 2005), they are sometimes attended by ants (Wagner 2005). Interestingly, harvester pupae do have well-developed stridulatory organs (Douglas 1986). The function of these organs in the pupae is not known.

The proboscis of harvester adults is very short, and they do not feed on floral nectar. Instead, they feed on aphid honeydew, dung, sap, and also sip from mud (Scott 1986). Because the adults are small in size, spend most of their time in the locality of their aphid prey, have an erratic flight, and do not feed at flowers, they are not commonly seen. Therefore, they are probably perceived as being more uncommon than they actually are (Wagner 2005).

Youngsteadt E, Devries PJ. 2005. The effects of ants on the entomophagous butterfly caterpillar Feniseca tarquinius, and the putative role of chemical camouflage in the Feniseca-Ant interaction. Journal of Chemical Ecology 31: 2091-2109.