VT a. Larva of the Yellowheaded spruce sawfly. The ground beneath trees may be littered with partially consumed needles and frass. When disturbed, larvae have a tendency to rear up both their head and tail ends, and they may give off a viscous fluid from the mouth. After larvae complete feeding, their droppings may still be seen and dark brown cocoons with bits of soil around them will be present in the litter.
Winter is spent in a prepupal stage in a cocoon in the litter.
Eggs are laid singly in slits at the base of new needles in the crown of the tree. Larval feeding lasts for about a month. Then larvae drop to the ground and spin cocoons. Parasites and predators are known to kill significant proportions of yellowheaded spruce sawfly populations, but control using insecticides is frequently necessary. Young, open-grown and ornamental trees seem to be preferred.