The larvae look like caterpillars (the larvae of moths and butterflies), with two notable exceptions; (1) they have six or more pairs of prolegs on the abdomen (caterpillars have five or fewer), and (2) they have two stemmata instead of a caterpillar's six. Typical sawfly larvae are herbivorous, the group feeding on a wide range of plants. Individual species, however, are often quite specific in their choice of plants used for food. The larvae of various species exhibit leaf-mining, leaf "rolling", or gall formation. Three families are strictly xylophagous, and called "wood wasps", and one family is parasitic. The larvae that do not feed externally on plants are grub-like, without prolegs.