This extensive order of insects is divided into two principal sections—those in which the ovipositor is used as a saw or an auger, and those in which it is modified into a sting. One of the most interesting sections of the Borers includes the Saw-flies, in which the boring instrument is modified into a pair of toothed saws, which are used for cutting incisions in leaves, or in the tender bark of twigs, in which to deposit the eggs. These flies have four transparent wings, sometimes stained with yellow or purple, and their bodies are moderately stout and obtuse, and generally black, red or yellow. The antennæ are very variable in form, and are sometimes knobbed at the end like those of a butterfly; sometimes they are formed of a number of long, slender joints; sometimes of only three—a moderately long basal one, a short middle one, and a long terminal one, composed of a number of joints united into one; and rarely, as in the case of the males of some small species about half an inch long which feed on fir and pine, the antennæ are feathered. The grubs are very like caterpillars, and are sometimes called "false caterpillars"; but a true caterpillar (except in one or two very rare exceptions among foreign species) has never more than sixteen legs, while these "false caterpillars" have more, often as many as twenty-two. They also resemble caterpillars in another way, for the pupæ are enclosed in cocoons. One interesting Australian species, which feeds on gum-trees, proceeds from a black caterpillar with only six legs. The perfect insect has a blackish head and thorax, with three large yellow spots on the latter, yellowish antennæ and wings, and a green abdomen; it measures about an inch and a half across the wings, and has knobbed antennæ. An allied species, found in Tasmania, is said to tend its young larvæ—an unusual habit, except among social insects like bees, wasps, and ants. Among the commonest and the most destructive saw-flies in England are those feeding upon the currant, gooseberry, and pear, of which there are several species, measuring about half an inch across the wings. The commonest flies which lay their eggs on the gooseberry and currant are yellow, with the head, antennæ, and three long spots on the back black, and the wings transparent, with black veins. The grubs are bluish green, with twenty legs, and numerous black dots; and several may often be seen on one leaf. The best-known of the Pear Saw-flies is black, with the wings transparent, except the veins; the grub is very like a slug, and is green or yellow, very slimy, with the front of the body much thickened.
Photo by W. P. Dando, F.Z.S., Regent's Park.
TREE-WASP.
Very similar to the common wasp, but builds its nest in trees instead of in the ground.
The Wood-wasps include only a few species, the grubs of which live in the stems of plants, or in the solid wood of trees. One of the largest feeds on fir- or pine-trees, and the fly measures from half an inch to an inch and a half in length, and varies much in size, though the male is generally much smaller than the female. The female is yellow, with two black bands, and a stout ovipositor half as long as the abdomen. In the male the tip of the abdomen is black, and ends in a rectangular point. The wings are transparent, with yellow nervures.
Photo by Scholastic Photo. Co.] [Parson's Green.
TREE-WASP'S NEST.
Generally built in a thick bush.