SUB-ORDER I. SYMPHYTA Abdomen with no definite basal constriction or waist: trochan ters two-jointed. Larvae generally caterpillars with a variable number of legs.
Superfamily Tenthredinoidea (fig. 5). Included in this division are all the more primitive members of the order : they do not exhibit the specialized habits and instincts of the Apocrita and their larvae are almost entirely plant-feeders. The most important family is the Tenthredinidae or saw-flies (q.v.) which are distin guished by two large spines or spurs to each fore tibia. Their larvae are caterpillars which feed upon the leaves of plants, and those of a number of species are injurious to cultivated plants and forest trees. The ovipositor is usually elaborately toothed, and is used for sawing notches to enable the eggs to be laid in plant tissues. The Cephidae or stem saw-flies are a small group, whose larvae feed in the stems of various plants, while those of the Siricidae or wood-wasps bore into the wood of trees.
