Adult Solomon’s seal sawfly are black-bodied insects, 8-9mm long, with two pairs of blackish grey wings. In appearance they are similar to medium sized flies but are in the same group of insects as the bees, ants and wasps, the Hymenoptera. They emerge in late spring at about the time when their host plant is coming into flower.
The female uses her saw-like eggs-laying organ to insert rows of eggs into the leaf stems. This causes vertical purplish brown scars to develop where the eggs were inserted.
The larvae feed together in small groups on the underside of the leaves. Initially they make small elongate holes but as the larvae increase in size, their appetite also increases. By mid-summer, the stems may have been stripped of foliage.
The fully fed larvae go into the soil where they overwinter and pupate in the following spring. Defoliated plants will survive but may produce reduced growth in the following year.