Saw Fly, the popular name of the tenthre-dinidoe, a very destructive family of hymenop-terous insects. They are found on the leaves of plants, and live almost entirely on vegetable food; they are poor fliers and sluggish; the form is generally short and flattened, with broad head, and thorax widely joined to the abdomen, the antennae short but of various forms, thread-like, knobbed at the end, feathered, notched, or forked; the wings overlap, cover the back, and are horizontal when closed. The females have two saws, lodged in a groove in the hind part of the body within two sheathlike pieces; they are placed side by side, with the ends directed backward, the form and the shape of the teeth varying; they usually curve upward, and are serrated along the lower or convex edges; each saw has a back to steady it, but the blade slides forward and backward on it; they are not only toothed on the edge but on the sides, acting as rasps as well as saws. With these they saw slits in stems, leaves, and fruits, in which their eggs are deposited; the wounds sometimes produce galls in which the young are hatched and grow.
The larvae look much like caterpillars, are cylindrical and greenish, with several pairs of legs, generally 18 to 22; most are naked, but some have a few prickles, others a white flaky substance, and a few a dark, slimy, slug-like skin. The larvae also resemble caterpillars in habits; when fully grown they enter the ground and make a silken cocoon, but a few place their cocoons on plants or in crevices above ground; they remain thus during the winter, change to whitish chrysalids in spring, and soon come out winged insects; there are sometimes two broods, one going through all its changes during summer. - About 100 species are found in New England alone. The largest is the elm saw fly (cimbex ulmi, Peck), about 7/8 in. long, with an expanse of wings of nearly 2 in.; the female resembles a hornet, with black head and thorax, hind body steel-blue with three or four yellowish spots on each side, and smoky brown transparent wings. The male is very different, and is the C. Americana of Leach; the body is longer and narrower, without the spots on the sides.
They appear from the last of May to the middle of June, the eggs being deposited on the American elm, whose leaves are eaten by the larvae; these in August are nearly 2 in. long, thick-bodied, with 22 legs, rough skin, pale greenish yellow, with numerous transverse wrinkles and black dorsal stripe and spiracles; when at rest they lie on the side in a spiral, and eject a watery fluid from lateral pores when disturbed; they make a tough cocoon under dead leaves, in which they remain all winter, being transformed to chrysalids in spring. The fir saw fly (lophyrus abietis, Harris) is very destructive in the larva state to the fir family in New England. The male is about 1/4 in. long and 2/5 in. in expanse of wings; black above, brown below, the wings with changeable tints of reddish, green, and yellow; the legs dirty yellow; antennae like short black feathers curled inward on each edge. The female is 3/10 in. long and 1/2 in. in expanse; yellowish brown above, with blackish stripe on each side of thorax; dirty yellow below; antennae short and tapering, 19-jointed, serrated on the outside.
They appear early in May, making slits for their eggs in the edges of the leaves; the larvae come out in June and July, living in large swarms, curling the hind part of the body around the leaf while feeding, and throwing up the head and tail when disturbed; they are about 1/2 in. long, the head and anterior parts black; body pale green with longitudinal stripes; below yellowish; they become almost yellow at last, and descend to the ground, where they make oblong grayish cocoons, 3/10 in. long, escaping in the spring by a lid at one end. The most effective means of destroying them is showering the trees with soap suds or a solution of whale-oil soap. A nearly allied species, L. pini (Latr.), is very destructive to the pine and fir in Europe; the eggs are laid in slits in the leaves closed up by a viscid substance which issues from the mouth; whole forests in Germany have been stripped by the larvae; among their enemies are insectivorous birds and mammals, like the woodpeckers, mice, and squirrels, and also ichneumon flies. The vine saw fly of the United States (selan-dria vitis, Harris) is black, with red thorax above, and fore legs and under sides of all the legs yellowish white; wings smoky; the female 1/4 in. long, the male smaller.
They lay eggs in the spring on the lower side of the terminal leaves of the vine, the larvae appearing in little swarms in July, feeding in company and eating the leaves even to the stalk; they are 5/8 in. long when full grown, the head and tip of tail black, the body light green above with two rows of black dots on each ring, and yellowish below; they make cells of earth lined with silk, and come out perfect insects in about two weeks, when they lay eggs for a second brood, which eat, go into the ground for the winter, and come out flies the next spring. The best remedies are dusting air-slacked lime on the vines or showering them with strong soap suds. Another saw fly injurious to fruit trees will be noticed under Slug Worm.
Elm Saw Fly (Cimbex ulmi).
Fir Saw Fly (Lophyrus abietis).