Sawfly, common name for members of insect order Hymenoptera, which resemble wasps and are characterized by the lack of a marked constriction between the first and second abdominal segments. Common name is derived from the sawlike ovipositor used by females to slit open host plants and lay eggs.


In Canada sawflies are found everywhere, especially in boreal regions. About 10 000 species are known worldwide; about 600 in Canada.


Larvae and most adults are herbivorous; adults of some species feed partly on other insects. Their plant-feeding habit may make sawflies important defoliators; however, surprisingly few species are recognized as regular threats to crops and forests. Most species feed on plants of little economic importance (eg, willows, sedges, wild grasses) or show irregular population explosions of limited extent.

Reproduction and Development

Larvae are caterpillarlike but are distinguished from true caterpillars by having smooth prolegs (false legs) on abdomen. Most species reproduce bisexually; in some, males are rare or unknown and reproduction is by parthenogenesis (development of offspring from unfertilized eggs).