cloud on the tips of its wings. Excepting in this respect, it closely resembles the dark-colored variety of Cynips oneratus, and very little exceeds it in size.

One of our smallest gall-flies may be called Cynips seminator, or the sower. She lays a great number of eggs in a ring-like cluster around the small twigs of the white oak, and her punctures are followed by the growth of a rough or shaggy reddish gall, as large sometimes as a walnut. When this is ripe, it is like brittle sponge in texture, and contains numerous little seed like bodies, adhering by one end around the sides of the central twig. These seeming seeds have a thin and tough hull, of a yellowish white color; they are egg-shaped, pointed at one end, and are nearly one eighth of an inch long. The gall-insects live singly, and undergo their transformations, within these seeds; after which, in order to come out, they gnaw a small hole in the hull, and then easily work their way through the spongy ball wherein they are lodged. They are less than one tenth of an inch long, are almost black, or of the color of pitch, highly polished, especially on the abdomen, and their mouth, antennæ, and legs are cinnamoncolored.

It has been observed that no tree in Europe yields so many different kinds of galls as the oak. Those which I have described are not all that are found on oaks in this country, and they seem to be sufficiently distinct from the galls of European oaks.

Round, prickly galls, of a reddish color, and rather larger than a pea, may often be seen on rose-bushes. Each of them contains a single grub, and this in due time, turns to a gall-fly, which may be called Cynips bicolor, the two-colored Cynips. Its head and thorax are black, and rough with numerous little pits; its hind-body is polished, and, with the legs, of a brownish red color. It is a large insect compared with the size of its gall, measuring nearly one fifth of an inch in length, while the diameter of its gall, not including the prickles, rarely exceeds three tenths of an inch.

Cynips dichlocerus, or the gall-fly with two-colored antennæ, is of a brownish red or cinnamon color, with four little longitudinal grooves on the top of the thorax, the lower part of the an

tennæ red, and the remainder black. It varies in being darker sometimes, and measures from one eighth to three sixteenths of an inch in length. Great numbers of these galls-flies are bred in the irregular woody galls, or long excrescences, of the stems of rose-bushes.

The small roots of rose-bushes, and of other plants of the same family, sometimes produce rounded, warty, and woody knobs, inhabited by numerous gall-insects, which, in coming out, pierce them with small holes on all sides. The winged insects closely resemble the dark varieties of the preceding species, in color, and in the little furrows on the thorax ; but their legs are rather paler, and they do not measure more than one tenth of an inch in length. This species has been named Cynips semipiceus.

Monstrous swellings of buds, and various other kinds of excrescences, may often be seen on plants; but my specimens of the insects producing them are not in a condition to be described. The foregoing account, however, will serve to illustrate the habits of some of our most common gall-flies, and explain the origin, forms, and structure of their singular productions. Such excrescences, as soon as they are observed on plants of any value, should immediately be cut off, and put into the fire. Fortunately the parasitical insects, that live at the expense of the fourwinged gall-flies, are almost or quite as numerous as the latter, and, as already stated, limit them in their powers of multiplication.

DIPTERA.

GNATS AND FLIES. MAGGOTS. - REMARKS UPON AND DESCRIPTIONS OF SOME OF the Diptera. — Radish-Fly. — Two-WINGED Gall-Flies, and Fruit-Flies.

- HESSIAN FLY WHEAT-FLY. CONCLUSION.

UNDER the name of DIPTERA, signifying two-winged, are included all the insects that have only two wings, and are provided with two little, knobbed threads in the place of hind-wings, and a mouth formed for sucking or lapping.

Various kinds of gnats and of flies are therefore the insects belonging to this order. The proboscis or sucker, wherewith they take their food, is placed under the head, and sometimes can be drawn up and concealed, partly or wholly, within the cavity of the mouth. It consists of a long gutter, usually ending with two fleshy lips, and enclosing, in the channel on its upper side, several fine bristles, from two to six in number, which are sometimes as sharp as needles, and are then capable of inflicting severe punctures. These piercing bristles really take the place of the jaws of biting insects, and hence the wounds made therewith, by gnats and mosquitos, are very properly called bites. The saliva of these insects flowing into the wounds, renders them more painful, and is the cause of the inflammation and itching that follow. The grooved sheath of the proboscis is usually very large and fleshy in the flies that only lap or sip their food. Two small, jointed feelers are commonly found attached to the base of the proboscis. Gnats and flies have softer bodies than most other winged insects. The head is large, and fastened to the thorax by a very slender neck. The eyes, especially in the males, are large, and occupy the whole of the sides of the head. The antennæ, in gnats and mosquitos, are rather long, slender, and many-jointed ; in flies, they are short, consisting of only two or three thick joints, the last of which often bears a little bristle or delicate feather. The wings are filmy, like those of Hymenopterous insects, but usually have a greater number of veins in them. Just behind the wing-joints there are two little, convex scales, which

open and shut with the motion of the wings; they are called the winglets. The two balancers or poisers are short threads, knobbed at the end, and placed on each side of the hindmost part of the thorax, immediately behind the winglets. The thorax is often the thickest and hardest part of the body; to it the hindbody is more or less closely united, and the latter, in many females, ends with a tapering, retractile tube, wherewith the eggs are deposited. The legs are six in number, and each of the feet is provided with two claws, and two or three little cushions or skinny palms, by the help whereof the insects can walk on the smoothest surfaces, and on the ceilings of rooms, with the back downwards, as easily as when upright; for the palms act like suckers, and thus prevent them from falling.

Mosquitos and gnats are active both by day and night, but flies take wing only during the day. The life of these insects, even from the time when they are first hatched, is generally very short, seldom lasting more than a few weeks; but of some kinds several broods are produced in the course of a single summer, and often in the greatest profusion. In certain countries and seasons they multiply so fast, and appear in such immense swarms, as to become a serious annoyance both to man and beast.

The young insects, hatched from the eggs of gnats and of flies, are fleshy larvæ, usually of a whitish color, and without legs. They are commonly called maggots, and sometimes are mistaken for worms. They vary a good deal in their forms, structure, habits, and transformations, so that it is somewhat difficult to give any general description of them. Their breathing-holes are usually situated near the extremities of the body. Aquatic maggots often have a tubular tail, through which they breathe, and the orifice of this tube is sometimes surrounded with beautiful featherformed appendages. The larvæ or maggots of the gnats, and of nearly all those flies which have four or six bristles in the proboscis, have a distinct head covered with a horny shell. Larvæ of this kind, when fully grown, cast off their skins to become pupa or chrysalids. These pupæ are usually of a brown color, and somewhat resemble the chrysalids of certain moths, or more nearly those of Hymenopterous insects; for their short and imperfect legs and wings, though folded on the breast, are not immova

bly fastened to it. They commonly have several small thorns on each end of the body, and a row of smaller prickles across each of the rings of the back. By the help of these thorns and prickles they work their way out of the places wherein they had previously lived, just before they burst open their pupa-skins to come forth in the perfected or winged state. The pupe of mosquitos are not prickly, but they possess the power of swimming or tumbling about in the water, by the help of two little fins on their tails.* The larvæ of the Dipterous insects in general do not make cocoons; those of some gnats (Mycetophila), which live in tree mushrooms, or boleti, not only cover themselves with a silken web, under which they live, but also spin cocoons, wherein they undergo their transformations. The larvæ of the other flies are not so variable in their forms as the foregoing. They are commonly plump, whitish maggots, obtuse behind, and tapering before, with a small and soft head, that can be drawn within the forepart of the body. They take their food almost entirely by suction, for their jaws are merely two little hooks, that enable them to fasten themselves upon the substances which serve for their nourishment. They increase rapidly in size, and when they are fully grown, they change their forms, without casting off their skins at all, merely by the gradual shortening of their bodies, which take an oblong oval shape, and turn hard and brown on the outside. The hardened skin of the larva thus becomes a shell or kind of cocoon, within which the insect is afterwards changed to a pupa, having its imperfect limbs folded on its breast, and from which, in due time, it comes forth in the form of a fly, by forcing off one end of the shell.†

In the introductory chapter‡ a short account has already been given of the habits of the various kinds of gnats and flies, belonging to the principal families of this order. Besides the few species that are injurious to vegetation, and are to be more fully described hereafter, there still remain some of our native flies, that deserve a passing notice, on account of their size, or of peculiarities in their forms, structure, and habits, although they are not to be included among the insects which are hurtful to plants.

* See pages 5 and 6.

+ See page 6.

+ Page 15.