Ailanthus Webworm

The Ailanthus webworm, Atteva aurea, is an ermine moth now found commonly in the United States. It was formerly known under the scientific name Atteva punctella (see Taxonomy section).

The Ailanthus webworm is thought to be native to South Florida and the American tropics (south to Costa Rica), habitat to its original larval host plants, the Paradise Tree (Simarouba glauca) and Simarouba amara. Another tree called Tree-of-Heaven (Ailanthus altissima), originally from China, has been widely introduced and Atteva aurea has jumped to this new host plant (giving it its common name, Ailanthus webworm). The moth does not survive cold winters, but migrates north each year so it is commonly seen in summer throughout the continental US, and occasionally eastern Canada (its northern limit in eastern Ontario and south-western Quebec beyond the host range).

Larvae produce nests on the host plant by pulling two to three leaflets around a network of loose webbing. Then they consume the leaflets. The caterpillars have a wide, light greenish-brown stripe down their backs and several thin, alternating white and olive-green stripes along their sides. The adult moth visits flowers, is diurnal, and is a pollinator.

Ailanthus, common-name Tree of Heaven, is considered an invasive species, although it is still sold by nurseries as yard plant, mainly because it is one of the species that will grow in polluted or otherwise difficult places. Atteva aurea can be a minor pest in nurseries, although it rarely does serious damage.