Mourningcloak Butterfly (Nymphalis antiopa)

From: Ostry, Michael E.; Wilson, Louis F.; McNabb, Harold S., Jr.; Moore, Lincoln M. 1988. A guide to insect, disease, and animal pests of poplars. Agric. Handb. 677. Washington, DC: U.S. Department of Agriculture. 118 p.

Importance- The larvae, feeding in clusters, consume large quantities of foliage and rapidly defoliate trees of all sizes in nurseries and plantations throughout North America. Trees are weakened from defoliation, and twice-defoliated trees may die or dieback and resprout.

Look For: One or more branches partly or completely devoid of foliage. Clusters of spiny, blackish, red-spotted larvae up to 2 inches long on the leaves and shoots.

Mourningcloak larvae Photo by USDA Forest Service - Alaska Archives

Biology- At least two generations occur each year. The butterflies hibernate; and as soon as the weather warms, the females lay masses of 300 to 450 eggs on poplar shoots. The larvae feed gregariously and consume all foliage except the largest leaf veins. Fully grown larvae from chrysalises on the shoots, and the distinctive black and yellow butterflies emerge within a week. The second generation follows and the adults overwinter.

Monitoring- Inspect trees in early summer and again in late August for spiny colorful caterpillars and injured leaves. Treat infested nursery beds when larvae are present. In plantations, treat each infested tree to reduce the population or wait until 10 percent of the trees are infested in the second generation.

Control: Allow parasites and predators to build up when larvae are not threatening the trees. Treat with a commercial preparation of Bt (Bacillus thuringiensis) as soon as larvae start feeding. Apply a chemical insecticide for leaf-eating larvae when the caterpillars are feeding.
Trees defoliated by mourningcloak larvae.	Webs and cast larval skins of the mourningcloak larvae.

This insect has many natural enemies that build up rapidly.

For Additional Information:

Becker, W.B. 1938. Leaf-feeding insects of shade trees. Bull. 353. Massachusetts Agricultural Experiment Station. 83 p.