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The forest tent caterpillar, native to North America, is unquestionably the most common leaf eater in hardwood forests. Found throughout the continent, its preferred host is trembling aspen (Populus tremuloides). However, during widespread outbreaks, it will attack all hardwood trees, except red maple (Acer rubrum).

Infested hardwood stands are identified by the presence of groups of characteristically colored caterpillars on the foliage and trunks of trembling aspen. During off season, egg bands on the twigs can easily be seen. Despite its voracious appetite, forest tent caterpillar outbreaks do not usually last more than 3–4 years.

Points of interest

• although they are called tent caterpillars, they actually spin a kind of veil or mattress on the surface of branches, a structure to which they can retreat and cluster as a group
• the first outbreak of this insect to be positively identified goes back to 1791
• records indicate outbreaks with an average of 10–12 years between intervals
• although complete defoliation may occur, typically this does not kill the tree

View the distribution map (1980–1995)

References

Martineau, R. 1984. Insects Harmful to Forest Trees. Multiscience Publications Ltd., Montreal, Environment Canada, Canadian Forestry Service, Ottawa, and Supply and Services Canada, Canadian Government Publishing Centre, Ottawa. For. Tech. Rep. 32. 261 p.+ x.

Rose, A.H.; Lindquist, O.H. 1997. Insects of Eastern Hardwood Trees. Natural Resources Canada, Canadian Forest Service, Ottawa. Revised edition. For. Tech. Rep. 29. 304 p.