Stout spanworm moth

Stout spanworm moth is a medium-sized, broad-winged, very hairy, typical geometer moth. It occurs in the northern United States and southern Canada from coast to coast. Its distribution is patchy and it is common at some locations (locally common).

Adults have a wingspan of 1 3 ⁄16″ to 1¾″ (30 to 45 mm). Males have plume-like antennae and broad wings. Females have thread-like antennae. Their wings are smaller than the male’s and they cannot fly. The thorax and abdomen are extremely hairy. The forewing is gray with fine black speckling (peppery); black antemedial (AM), median, and postmedial (PM) lines; and a white subterminal line. The hindwing is similar but the markings are muted.

The caterpillar is up to 1 9 ⁄16″ (4 cm) long and, as the common name suggests, is stout. It is pinkish and has many fine, wavy, longitudinal, black stripes. It has yellow breathing pores (spiracles); yellow, round warts above the spiracles (supraspiracular area); and yellow, dash-like warts above on each side (subdorsal area). The legs and the head are reddish.

Wingspan: 1 3 ⁄16″ to 1¾″ (30 to 45 mm)

Deciduous and mixed woodlands

One generation per year: Early April to late May

Males are active at night and will come to lights. Females cannot fly. Wings are held flat when at rest.

Eggs are laid under bark. The pupa overwinters.

Leaves of deciduous trees and woody plants, including alder, apple, ash, basswood, birch, blueberry, cherry, cranberry, dogwood, elm, hawthorn, maple, poplar, and willow.