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My Sphecomyia undata has the slender form of a Sphex or mud-wasp. It is of a light brown color, darker on the back, and on the middle of the thighs and shanks; its head is conical, and bears the antennæ on the tip of the cone; its wings are brown on the outer part, with a small transparent spot near the edge, and the inner part is transparent in two large wavy spaces. It is about five eighths of an inch long, and its wings expand one inch and a quarter, or more. It is possible that this singular fly may be the Pyrgota undata of Wiedemann. An insect, closely resembling it, is figured in Griffith's translation of Cuvier's “ Animal Kingdom," under the name of Myopa nigripennis. It is found on fences around gardens in May and June. It sits with its wings half spread, moves slowly, and fies heavily. My Sphecomyia valida, though rather shorter than the preceding, has a thicker body. Its color is brownish yellow, and it is striped with brown. The wings are transparent, and are mottled with small, dusky spots.
Some of the Conopians (Conopida) still more closely resemble slender-bodied wasps than the preceding Sphex-flies. Conops sagittaria, of Say, (nigricornis, Wiedemann) might almost be mistaken for a species of Eumenes. Its hind body is very slender and cylindrical next to the thorax, and swells out behind. Its antennæ are long, and thickened towards the end. Its proboscis is very long and slender, elbowed at the base, and extends far beyond the head. This fly is of a black color; the rings of the hind body are edged with white; the face is yellow; the legs are brownish yellow, shaded with black on the thighs; and the wings are black, with two uncolored and wavy spaces on the inner margin. Its body is five eighths of an inch long, and its wings expand rather more than three quarters of an inch. This fly may be found sucking the honey of flowers in June and July. The Greeks gave the name of Conops to some stinging fly or gnat. The Conopians undergo their transformations in the bodies of humblebees, their young subsisting on the fat contained within the abdomen of their luckless victims.
A host of flies, forming nearly one third of the whole number of species in the order Diptera, will be found to have a short and soft proboscis, ending with large fleshy lips, enclosing only two bristles, and capable of being drawn up within the cavity of the mouth. Their antennæ are generally short, hang down over the face, and end with a large oval joint, bearing a little bristle. Their larvæ, or young, are fleshy, whitish maggots, which never cast their skins, but when the pupa-state comes on, shorten, take the oblong oval form of an egg, and become brown, dry, and hard on the outside. This immense tribe includes the various kinds of flesh-flies, blow-flies, houseflies, dung-flies, flower-flies, fruit-Alies, two-winged gall-flies, cheese-flies, and many others, for which we have no common names, but all composing the tribe of Muscans, or MUSCADÆ. Some of these flies do not strictly conform to the foregoing characters of the tribe, in all respects; but the exceptions are few in number, and the most remarkable of them will be noticed in the following pages.
Many flies of this tribe are parasitic in their larva state, their young living and undergoing their transformations within the bodies of other insects, particularly in caterpillars, which they thereby destroy. These flies belong chiefly to the family of TachiNADÆ, a name applied to them on account of the swiftness of their flight. In form they somewhat resemble houseflies; like them they have very large winglets, and their wings spread apart when they are at rest. They are easily distinguished, however, by the stiff hairs wherewith they are more or less covered, and by the bristles on their antennæ, which are not usually feathered. A large fly of this kind, the Tachina vivida of my “Catalogue,” is often seen on fences, and on plants, and sometimes in houses, towards the end of June and during the month of July. Its large, oval hind body is of a clear and light red color, with two or three black spots, in a row, on the top of it, and a thick row of black bristles across each ring. The face is grayish white, like satin, and the eyes are copper-colored. The thorax is gray, with brownish lines upon it. The antennæ, proboscis, and legs are light red. Its body is short and thick, and is about half an inch long, and its wings expand rather more than nine tenths of an inch.
Most insects are hatched from eggs which are laid by the
mother on the substances that are to serve for the food of her young. Some flesh-flies produce their young alive, or already hatched, and drop them on the dead and putrefying animal matter, which they are to consume and remove in the shortest possible time. An exception from the usual course among insects appears therefore to have been made in favor of these viviparous Aesh-flies, to enable their young promptly to perform their appointed tasks. These insects produce an immense number of young, as many as twenty thousand having been observed by Réaumur in a single fly." Our largest viviparous flesh-fly is the Sarcophaga Georgina of Wiedemann. It appears towards the end of June, and continues till the middle of August, or perhaps later. Its face is silvery white, and there is an oblong square black spot between the eyes, which are copper-colored. The thorax is light gray, with seven black stripes upon it. The hind body is nearly conical, has the lustre of satin, and is checkered with square spots of black and white, shifting or interchanging their colors according to the light wherein they are seen. The legs are black, and the hindmost pair are very hairy in the males. The female is about half an inch long; the male is rather smaller. In the Sarcophagans, or flesh-eaters, as the name implies, the bristles on the antennæ are feathered.
The flies that abound in stables in August and September, and sometimes enter houses on the approach of rain, might be mistaken for house-flies, were it not for the severity of their bites, which are often felt through our clothing, and are generally followed by blood. Upon examination they will be found to differ essentially from house-flies in their proboscis, which is very long and slender, and projects horizontally beyond the head. The bristles on their antennæ are feathered above. Cattle suffer sorely from the piercing bites of these flies, and horses are sometimes so much tormented and enraged by them as to become entirely ungovernable in harness. The name of this kind of fly is Stomoxys calcitrans; the first word signifying sharp-mouthed, and the second kicking, given to the fly from the effect it produces on horses. It lays its eggs in dung, where its young are hatched, and pass through their transformations. The larvæ and pupæ do not differ much in appearance from those of common house-flies.
* “ Mémoires," Vol. IV., p. 417.
The next three flies have feathered bristles on their antennæ. The first of them, a large, buzzing, and stinking meat-fly, named Musca (Calliphora) vomitoria, is of a blue-black color, with a broad, dark blue, and hairy hind body. It is found all summer about slaughter-houses, butchers' stalls, and pantries, which it frequents for the purpose of laying its eggs on meat. The eggs are commonly called fly-blows; they hatch in two or three hours after they are laid, and the maggots produced from them come to their growth in three or four days, after which they creep away into some dark crevice, or burrow in the ground, if they can get at it, turn to egg-shaped pupæ, and come out as flies, in a few days more; or they remain unchanged through the winter, if they have been hatched late in the summer. A smaller fly, of a brilliant blue-green color, with black legs, also lays its eggs on meat, but more often on dead animals in the fields. It seems hardly to differ from the Musca (Lucilia) Cæsar of Europe. The house-fly of this country has been supposed to be the same as the European Musca domestica; but I cannot satisfy myself on this point for the want of specimens from Europe. It is possible that our sharp-biting stable-flies, the meat-flies, and the house-fly, may really be distinct species from those which are found in Europe. Our house-fly is the Musca Harpyia, or Harpy-fly, of my “Catalogue.” It begins to appear in houses in July, becomes exceedingly abundant in September, and does not disappear till killed by cold weather. It is probable that, like the domestic fly of Europe, it lays its eggs in dung, in which its larvæ live, and pass through their changes of form. The Americans are accused of carelessness in regard to flies, and apparently with some reason. But, if these filthy, dung-bred creatures swarm in some houses, covering every article of food by day, and absolutely blackening the walls by night, in others comparatively few are found; for the tidy housekeeper takes care not to leave food of any kind standing about, uncovered, to entice
them in, and makes a business of driving out the intruders at least once a day. If a plateful of strong green tea, well sweetened, be placed in an outer apartment accessible to flies, they will taste of it, and be killed thereby, as surely as by the most approved fly-poison. In the first volume of “The Transactions of the Entomological Society of London,” Mr. Spence gives an account of a mode of excluding flies from apartments, which has been tried with complete success in England. It consists of netting, made of fine worsted or thread, in large meshes, or of threads alone, half of an inch or more apart, stretched across the windows. It appears that the flies will not attempt to pass through the meshes, or between the threads, into a room which is lighted only on one side; but if there are windows on another side of the room they will then fly through; such windows should therefore be darkened with shutters or thick curtains.
The Anthomyians, or flower-flies (ANTHOMYIADA), are easily distinguished from the preceding flies, which they otherwise resemble, by the smaller size of their winglets, and by the mesh in the middle of their wings, which is long, narrow, and
open at the end. They are smaller insects than the foregoing, their flight is more feeble, their wings, when at rest, do not spread so much, and the bristle on the last joint of their antennæ is not often feathered. Most of them frequent flowers, and are sometimes seen sporting together, in large swarms, in the air, like certain kinds of gnats. In the larva state some of them live in manure, and in rotten vegetable substances; others are found in the roots of living plants, such as onions, radishes, turnips, and even in the pulpy parts of leaves and of stems, which they devour. The latter have nearly the same form as the maggots of common flies; some of the former are shorter, flattened, and fringed on the sides with feathery hairs.
Many instances are recorded of these fringed maggots having been discharged from the human body. They are supposed to be the young of a fly named Anthomyia (Homalomyia) scalaris.*
For an account of the transformations of the fly of privies, with figures, see Swammerdam's "Book of Nature," translated by Hill, Part II., p. 38, plate 38.