sawfly, common name for insects of several families of the order Hymenoptera, which also includes the ants, wasps, and bees. Sawflies are named for the two sawtoothed blades of the female's ovipositor that are used for slitting leaves or stems in order to deposit the eggs. The insects have two pairs of membranous wings and chewing mouthparts. Both the sawfly and the closely related horntail, whose burrowing larvae are the hosts of the ichneumon fly, lack the characteristic constricted abdomen of other hymenopterans. Sawfly larvae resemble caterpillars; some are leaf and stem borers, many feed on the surface of foliage, and others produce galls. Various species are destructive to larch, spruce, broadleaved fruit and shade trees, shrubs, and grasses. Most species have a single generation a year; they pass the winter either as larvae or as pupae in a cocoon or in some protected place. Sawflies are classified in the phylum Arthropoda, class Insecta, order Hymenoptera.

Any of numerous, widely distributed insect species in five families (superfamily Tenthredinoidea, order Hymenoptera). Typical sawflies (family Tenthredinidae) are often brightly coloured and are commonly found on flowers; the North American pear slug eats pear, cherry, and plum leaves. The larvae of many species in the other four families also damage trees. Argid sawflies (family Argidae) feed on rose bushes and willow, oak, and birch trees. The North American elm sawfly (family Cimbicidae) feeds on elm and willow. The North American conifer sawflies (family Diprionidae) are common, sometimes serious pests of coniferous trees. The pergid sawflies (family Pergidae) consist of a single genus in South America and Australia.

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