When mature the larvae spin tough capsule-like cocoons on the ground or in the litter, sometimes on the tree. The wasp-like adults emerge from these and lay eggs singly in slits cut in the needles. These slits are cut by a saw-like ovipositor used to deposit the eggs, hence the common name sawflies. This is one of the most widespread and destructive of the native species attacking pine. It is often abundant in northern New York State on red pine.
Pines having needles in clusters of two or three are preferred.
Host plants are red, pitch, Scotch, Austrian, mugho, jack, loblolly, slash, Japanese red and Virginia pines. Occasionally Eastern white pine may be attacked. Newly hatched larvae are whitish, faintly marked and with brownish heads. After molting the bodies become yellowish white with six rows of conspicuous black spots and the head becomes reddish. The life history is complicated, as there may be more than one generation a year.