noun
: any of numerous sawflies that infest the willow: as
a. : a large American sawfly ( Cimbex americana ) whose larva is pale greenish with a black dorsal stripe
b. : a steel-blue sawfly ( Dolerus arvensis ) or a related smaller brownish fly ( D. bicolor )
c. : a black sawfly ( Nematus ventralis ) whose yellow-spotted blackish larva infests also the wild cherry