The life cycle of the Cimbex americana takes place on a variety of different trees (ranging from maple and elm to apple and plum) but adult sawflies primarily lay eggs on willows and elms. In most cases, only one generation hatches per season, although sometimes larvae in the cocoon stage do not hatch the first spring, thus making it possible for two generations to hatch in one season (Borror et al. 1989).  After mating, the female sawfly slices the underside of leaves and lays her eggs.  She can lay 50 to 130 eggs at once, depositing as many as 12 eggs on one leaf.  In 7-10 days larvae hatch and feed on the leaves and for nutrients (Barnes 2010).

Mature larvae are about 2 inches long and have a distinct black stripe down their yellow bodies, along with more than five pairs of prologs, or abdominal limbs.  Although they highly resemble caterpillars, they are not related; unlike true caterpillars, the prologs of the sawfly lack a hook-like structure and they only have one eye on each side of the head (Barnes 2010). 


Larvae finished grazing on the leaves drop to the base of the tree in search of pupation sights in the dirt and grass.  Once happily settled, they begin to form cocoons for the winter months where they become known as prepupae (non-feeding larvae).  The prepupae emerge to become butterflies and moths, a transformation called pupation, which occurs the following spring. Adults typically emerge two weeks after pupation (early May to the middle of June) (Barnes 2010).









The newly matured adult sawfly uses its mandibles to cut into the limbs of sap-containing trees to obtain nutrients.  By the end of September and October the sawfly is ready to mate (U.S. Department of Agriculture 1974).