Spruce budworm

The adult moth has a wing span of 2 centimeters. It is usually grayish with dark brown markings. Some moths are brown or reddish with gray markings. Males and females occur in about equal numbers.
The light green eggs are about 1 millimeter long by 0.2 millimeter wide. The eggs, laid in elongate masses of 2 to 60 - averaging about 20, overlap one another.
Larvae go through six instars. The first larval instar, about 2 millimeters long, is yellowish green with a light- to medium-brown head. The second instar is yellow with a dark brown or black head. During the next four in-stars, the body of the larva changes from a pale yellow to a dark brown with light-colored spots along the back. In the sixth instar, the larva is about 2.5 centimeters long and the head is dark brown or shiny black. The pupa is pale green at first, later changing to reddish brown. It is marked with darkened bands and spots.
Life History and Habits. There is one generation of the spruce budworm each year. The female moth lays eggs on the flat undersurface of balsam fir or spruce needles, generally within 3 inches of the buds or defoliated area. In extremely high populations, eggs may be laid on almost any surface. Eggs are distributed more evenly on foliage of host trees in the Northeastern United States and eastern Canada than on those of western species. The eggs hatch in about 2 weeks. Usually, newly hatched larvae immediately seek a suitable place to spin their hibernacula or cocoon-like shelters. However, during warm periods, larvae may move about and feed on needles before spinning a hibernaculum. In doing so, they may spin down from a branch on a silken thread and be carried away by air currents. Larval dispersal at this stage is one means of spread within and beyond the infested stands. The young larva transforms into the second instar or stage within the hibernaculum and remains dormant over the winter. Old staminate flower bracts are preferred as overwintering sites, but bud scales and bark crevices are also used.
In the spring-after several days of warm weather, but before the balsam fir buds begin to expand - the larva emerges from hibernation and begins feeding. Early feeding is first confined to the new buds of staminate flowers if present, or the larva mines the previous year's needles if staminate flowers are scarce. The new flower buds provide a ready source of food before the vegetative buds expand. The early emerging larvae that feed on staminate flower buds grow much more rapidly and have a higher survival rate than those that feed on old needles.
The larva migrates to the end of a twig and bores into a needle or an expanding vegetative bud. Some larvae spin down on silken threads and, as first instar larvae, may be dispersed by air currents. The larvae feeding on staminate flower buds and flowers stay in place until the immediate food supply is depleted. Later, the larva feeds on the new foliage of developing shoots. When the larva is in the fifth instar, it begins tying the tips of twigs together with silk, forming a small nest. The new foliage is eaten first. In epidemic situations, old needles and bark (near branch tips) may also be consumed to such a degree that branch tips and terminal shoots are destroyed. During late June through mid-July, depending on the weather, the larva completes development and stops feeding.
The larva then transforms to a pupa, generally within the last-formed webbing. Some pupae are found at the axils (needle base) of the twigs. The moth emerges about 10 days later (in late June through mid-July). Peak moth flight activity occurs from about 7:30 p.m. to 11:30 p.m. Moths may be carried up to 10 miles or more by winds and can be transported hundreds of miles by storm fronts.