Forest Pests: Insects, Diseases & Other Damage Agents

Larch Silkworm (Hyalophora columbia columbia)

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.

Description. Green body with prominent, paired dorsal tubercles and smaller lateral ones. Green head with bluish labrum and with short dark line at sides of frons; four small black spots in bluish anterior half of prothoracic shield. Spined, reddish and black tubercles on T2, T3, and A1; white dorsal tubercles on A2 to A7 tinged with yellow near tip; large, white middorsal tubercle on A8 with black spots and with yellow tint at tip. White supraspiracular and subspiracular tubercles with blue base; white spiracles; prolegs larger on A10 than on other segments. Up to 90 mm.

Food. Eastern larch.

Life Cycle. One generation. Pupa overwinters in compact, silken cocoon on branch or trunk of tree or shrub. Mature caterpillar present from July to September.

Comments. The larch silkworm is a northern subspecies, occurring in the Great Lakes States, northern New York, northern New England, and southern Canada. Records of this subspecies from other woody plants probably came from caterpillars that were seeking a site for pupation.

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