one of two suborders of the insect order Hymenoptera, the other being Apocrita. Included in the group are the sawfly, horntail, and wood wasp (qq.v.)—the most primitive members of the order. The suborder includes several thousand species and is distributed worldwide.

The “waist,” or midsection, between the abdomen and thorax, is broad in Symphyta. The females have a well-developed ovipositor, or egg-laying organ. The larvae usually resemble caterpillars and have a variable number of legs. All are phytophagous (i.e., plant eating) except for members of the parasitic wood wasp family Orussidae (sometimes Oryssidae), a small, rare group.

Most species have one generation each year and spend the winter as a full-grown larva or as a pupa. Certain large species require more than one year to develop. Many forms, particularly the sawflies, are often highly destructive to food crops, timber, and other plants useful to man.