Introduced pine sawfly spend the winter in cocoons on foliage, twigs, and other substrates. Look for defoliation of current year's and older foliage.
Young larvae feed in groups, while older larvae feed singly.
There are two generations per year. Pupation takes place in early spring, and adults emerge during May and early June. Eggs are laid in slits in needles. Trees of all ages are attacked, but the insect seems to prefer ornamental, nursery, or plantation trees. First generation larvae prefer previous year's needles but second generation will feed on old and current year foliage.