Forest Pests: Insects, Diseases & Other Damage Agents

Ermine Moths (Family Yponomeutidae)

Maier, C.T., C.R. Lemmon, J.M. Fengler, D.F. Schweitzer, and R.C. Reardon. 2004. Caterpillars on the Foliage of Conifers in the Northeastern United States. FHTET-2004-1. Morgantown, WV: USDA Forest Service, Forest Health Technology Enterprise Team; 151 p.

The caterpillars in this small family are identified by the arrangement of crochets on their prolegs and by their chaetotaxy. They have a single pair of prolegs on A3 to A6 and A10; needleminers may have the prolegs reduced in size. Yponomeutids usually have a distinct anal plate. Mature caterpillars average 15 mm in length, although some may be greater than 35 mm.

Many species have gregarious caterpillars that live in webs spun over foliage or flowers. Most caterpillars eat the leaves or flowers of non-coniferous plants. After they complete their feeding, they change to pupae in their communal webs. The solitary caterpillars of Ocnerostoma and Zelleria feed upon conifers by mining or boring into the foliage of trees, especially those in the Cupressaceae and the Pinaceae.

The moths, which are small to medium in size, sometimes have their wings spotted. The adults fly between dusk and dawn.

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