Sawflies
(Tenthredinidae). A large section of Hymenoptera (see Insects), characterised by the females possessing an organ adapted to cut through the skin of leaves and of branches, so as to permit of eggs being placed in the slits. This organ resembles a minute double saw (whence the popular name of the insects), and is toothed so as to serve as one, but the details of the toothing vary with the species. The larvae of all feed on plants. Most of them greatly resemble the larvae of Butterflies and Moths, except in having from eighteen to twenty-two claspers or prolegs. Nearly all the larvae feed on leaves, exposed on the surfaces or the edges of the latter; but some burrow between the surfaces of the leaves (e.g., Fenusa Ulmi), and others live protected in the interior of fleshy pea-shaped or bean-shaped galls on the leaves (e.g., Nematus gallicola), or swellings in the branches, of Willows. When full grown, most of them go underground, spin cocoons there, and in them become pupae. Some (e.g., Trichiosoma lucorum and Lyda) fix their cocoons to branches of the food-plants, or spin up among dead leaves or rubbish. The larvae of the Rose-leaf Sawfly and of the Gooseberry and Currant Sawfly are good types of Sawfly larvae. In like manner, the Gooseberry and Currant Sawfly (Nematus Ribesii,) is a good type of a large majority of the mature Sawflies. Sawflies are mostly sluggish and heavy in their movements, even on the wing. The head is usually broad; and there is no narrowed foot-stalk between the thorax and the abdomen. The colours are very generally black, yellow, or brown on the body and limbs; the wings are almost always transparent, and are of the form shown. The largest Sawflies in Britain are about as large as a small Humble Bee, but most are of small size.
Many species are very harmful to cultivated plants; and references will be found to the worst under Gooseberry and Currant Sawfly, Lophyrus, Lyda, Nematus, Pear (INSECTS), Rose Sawflies, Slugworms, and Turnip Sawfly. Among the plants that suffer most are Coniferae, Currants and Gooseberries, Hawthorns, Roses, fruit-trees, Willows, and Turnips; but few plants altogether escape injury. Certain species of Sawflies, injurious to cultivated produce, feed exposed on the plants, and may be hand-picked; or, if very numerous, and if circumstances permit, they may be destroyed by watering the plants with infusions of powder of Hellebore, or of Paris Green. Social larvae, as in the genus Lyda, which spin a common web, may be removed and destroyed with the web. For further information, see the headings just quoted.