NC State Extension Publications

Description and Biology

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The ailanthus webworm, Atteva aurea, is the immature stage of an ermine moth, a small (1/2 inch), yellow-orange insect traversed by four blue-black bands marked with conspicuous white spots on the wings. The wings are held tight against the body when not in flight. Ailanthus webworms are slender, brown to almost black, and sometimes have four white dots on the top of each segment. The head is noticeably lighter in color and may also have white spots. Some thin white and olive-green stripes might show along each side of the abdomen. They spin a frail silken web on the leaves of ailanthus. Moths mate in the morning, and female moths lay their eggs in the webbing usually in the evening. When mature, webworms molt into pupae that are also suspended in the loose webs. The caterpillars remain in the web during the day, but leave it to feed at night. During the growing season, all stages may be found in a web. Development from egg to moth takes about a month, so we have several generations per year in North Carolina. Eggs overwinter and hatch in mid to late spring.

Ailanthus webworm moth on goldenrod

Ailanthus webworm moths are brightly marked.

Richard Gardner,

ailanthus webworm moth on sedum flowers

The yellow-orange of this ailanthus webworm moth clashes with the pink sedum flowers completely disrupting the feng shui of this otherwise lovely photo.

Ward Upham, Kansas State University,

Two darker ailanthus webworms

Typical ailanthus webworms.

Richard Gardner,

A pale ailanthus webworm in its flimsy web.

This ailanthus webworm is pale perhaps because it recently molted.

Richard Gardner,

An ailanthus webworm pupa (with a young webworm to its left)

Ailanthus webworms pupate in their webbing.

Richard Gardner,

Host Plants

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Although Ailanthus trees have a wonderful common name (tree of heaven), in North Carolina they seem to be more of a weed tree growing in vacant lots and in cracks in pavement. The ailanthus webworm also infests paradise tree, Simarouba glauca, as well as Simarouba amara. Adults are considered good pollinators as they visit many species of flowers during the daytime.

An ailanthus webworm moth near some new webbing.

Ailanthus webworms loosely tie leaves together with silk strands.

Richard Gardner,

Ailanthus webworm and their messy webbing

By mid summer, ailanthus webworm webs can be large and messy.

Richard Gardner,

Residential Recommendations

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The ailanthus webworm has not been reported to be resistant to insecticides. Most of the insecticides labeled for landscape use found in the garden sections of big box stores should give more than adequate control.

Other Resources

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For assistance with a specific problem, contact your local N.C. Cooperative Extension center.

This Factsheet has not been peer reviewed.


Professor Emeritus
Entomology & Plant Pathology

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Publication date: March 11, 2019
Revised: Dec. 20, 2023

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