Species Alsophila pometaria - Fall Cankerworm - Hodges#6258

6258

Alsophila pometaria (Harris, 1841)

wingspan of males 26-32 mm (1); females about 9-10 mm long (CBIF)

Males have an even brownish grey forewing with jagged white and dark PM and AM lines, occasionally with a visible dark discal spot. The hindwings are light grey, with a dark discal spot and a faint pale PM line (AEC):

  

The females are wingless and stout-bodied, with the body banded dark and pale gray (1):

  

Larvae have 3 pairs of abdominal prolegs (1):

  

Wooded areas including city parks, ornamental plantations and shelter belts. (AEC)

Fall through early winter

Larvae feed on a large variety of deciduous trees and shrubs, especially elm (Ulmus spp.), ash (Fraxinus spp.), and maple (Acer spp.). (AEC) Other hosts include hackberry, oak, various members of the rose family, walnut, and willow. (1) Also Triosteum aurantiacum.

The larvae are often a serious pest of many tree species elsewhere, although it rarely reaches densities high enough to do damage in Alberta. The eggs are laid in clusters on tree branches and trunks by the wingless females and hatch the following spring, synchronized with the flush of leaves. There are four larval stages, which are described in detail by McGuffin (1988). Larvae pupate in the soil and delay their emergence until fall, spending about four summer months as a pupa. Females in at least some populations are able to reproduce parthenogenetically (without mating). (McGuffin 1988). (AEC)

Adult pairs:

Eggs; female with eggs; larva; pupa; adult male; adult female

Two wasps in the Scelionidae family are parasites on these eggs: Telenomus geometriae and T. alsophilae. (2)

Other geometrids have flightless adult females. Of those found in the fall, linden looper (Erannis tiliaria) is also wingless but is easily distinguished by its black markings. Operophtera spp. have small vestigial wings; these are conspicuous on winter moth (O. brumata) but can be minute and difficult to see on Bruce spanworm (O. bruceata). Females of spring cankerworm (Paleacrita vernata) are similar to fall cankerworm but appear in late winter and spring, at least in the north.