or deep brown, and the tail is furnished with two long bristles. This insect, which is common in many parts of Europe, is com. memorated as a most remarkable instance of the brevity of animal life; since after its change into the perfect animal it survives but a very few hours, perishing in the course of the same evening that gave it birth. It is to be recollected, however, that its larva lives in its aquatic state two, and even sometimes nearly three years; and is in this state so tenacious of life that Swammerdam assures us, that one which he pierced with a pin, to a board, in order to preserve it, lived all the next day notwithstanding. According to the figure given by Swammerdam, it is extremely allied to the larva of the ephemera vulgata; residing chiefly in tubular cavities, which it forms in the mud or clay of the waters it inhabits, occasionally coming out in quest of food. In this respect it agrees with the larvæ of several others of this genus, which have a similar habit of forming tubular hollows in the banks of their native waters. When arrived at full growth, the larva, or, more properly, pupa, rises, like that of the common ephemera, to the surface of the water, generally between the hours of six and seven in the even. ing; and the skin of the back cracking, and springing off with an elastic motion, the fly is almost instantaneously evolved, as in the common species; after which it flies to the nearest convenient spot, and again divesting itself of its pellicle, appears in its perfect or ultimate state. It now flies again to the water, and flutter. ing over its surface, as if sporting with its innumerable compa. nions, enjoys all the pleasures of its short remainder of existence; the female breeds, deposits her eggs, and, like the male, perishes before, or with the dawn of the approaching day.

This species, according to Swammerdam, is extremely frequent in the mouths or entrances of the Rhine, the Maes, the Wael, the Leck, and the Isel. It appears in the fly or perfect state about midsummer, and the season of its appearance lasts only three days, none being seen again till the following year.

[Swammerdam. Shaw.

SECTION XI.

Gnat. Musquito.

Culex pipiens.-LINN.

THE Common gnat is produced from an aquatic larva of a very singular appearance, and which, when first hatched from the egg*, measures scarcely more than the tenth of an inch in length. In the space however of fourteen days, it arrives at the length of something more than half an inch. In this state the head is very large, and furnished on each side with a pair of jointed processes resembling antennæ; the thorax large and angular; the body sud. denly lessening from this part, and continuing of nearly equal diameter to the tail, which is of an abruptly truncated figure, and tipped with four foliaceous processes: before the setting on of the tail is a long, tubular, projecting process, nearly at a right angle from the abdomen, and terminating in a tubular opening, verged by four ovate scales, two of which exceed the rest in size: the whole animal is of a brownish colour, semitransparent, and beset on each side the head, body, and tail, with large tufts of hair: its motions are very lively, and are conducted with a kind of convul. sive rapidity, in different directions, and to a small distance at a time. It feeds on the minute vegetables, and animal particles, which it finds in plenty in the stagnant waters in which it resides; and, when arrived at its full growth, casts its skin, and commences chrysalis, the aspect of which is hardly less singular than that of the larva, the head and thorax appearing connate, and exhibiting a large oval mass at the upper part of the animal, while the whole body bends downwards beneath the thorax is furnished on each side with an upright short tube or spiracle, and it is from these parts that the animal frequently hangs suspended from the surface of the water: the tail is tipped with a pair of leaf-shaped processes. This chrysalites, like the larva from which it proceeded,

* The eggs of the gnat are deposited in close-set groupes of three or four hundred together, and are very small, of a brown colour, and of a cylindric shape, with pointed tips: the whole groupe is placed on the surface of the water, close to the leaf or stalk of some water-plant.

is loco-motive, springing about the water nearly in a similar manner. When ready to give birth to the included gnat, which asually happens in the space of three or four days, it rises to the surface, and the animal quickly emerges from its confinement.

The gnat is supposed to feed both on animal and vegetable juices, but perhaps chiefly on the latter; since, as Reaumur ob. serves, of the millions on millions which swarm in the marshy regions where they are evolved, it can rarely fall to the lot of one in a hundred to taste blood once in its life.

The inconveniences, and even torments, experienced from these insects, in some parts of the world, are hardly to be conceived by those who inhabit the more favoured regions of the European continent. Instances have often been known to occur, of persons whose faces or limbs have been thrown into such a severe inflam. mation, as even to threaten the most serious consequences.

A warm rainy season is most favourable to the evolution of gnats; and, in such summers, particular districts in most countries are occasionally pestered by their legions. In the Philosophical Transactions, for the year 1767, we have an instance of this kind in the neighbourhood of Oxford, communicated by the late learned Mr. Swinton, of that University.

Oxford, November 15, 1766.

"The gnats have been more numerous, as well as more noxi ous, here, during the months of July, August, and September, 1766, than perhaps they were ever known before in the memory of man. So many myriads of them have sometimes occupied the same part of the atmosphere, in contiguous bodies, that they have resembled a very black cloud, greatly darkened the air, and almost totally intercepted the solar rays. The repeated bites likewise of these malignant insects have been so severe, that the legs, arms, heads, and other parts affected by them, in many persons, have been swelled to an enormous size. The colour also of these parts, at the same time, was red and fiery, perfectly similar to that of some of the most alarming inflammations.”

Mr. Swinton adds, that the swarms of these animals were ob served to ascend in columns of at least fifty or sixty feet in height. But of all the European nations, that of Lapland seems to be

the greatest sufferer from these vexatious animals; which, during the beats of the short summer, fill the air with such swarming myriads, that the poor inhabitants can hardly venture to walk out of their cabins, without having first smeared their hands and faces with a composition of tar and cream, which is found by experi. ence to prevent their attacks. Yet even this seemingly unfavour. able circumstance may be considered, in another point of view, as constituting one of the advantages of the country, being, in the expressive words of Linnæus, "Lapponum calamitas felicissima," since the legions of larves which fill the lakes of Lapland form a delicious and tempting repast to innumerable multitudes of aquatic birds; and thus contribute to the support of the very nation which they so strangely infest.

It may be added, that the formidable insect called the musquito, so much dreaded by the inhabitants of the West Indies, and America, where its bite seems to operate with peculiar malignity, is supposed to be no other than a variety of the common European gnat, which derives additional vigour from the warmer and moister atmosphere of the regions of the western hemisphere.

The true structure of the proboscis or piercer of the gnat, which, in its immediate operation, produces no very acute pain, but which is so often succeeded by such troublesome consequences, is not very easily determined. It seems however to consist of an external scaly sheath or tube, longitudinally divided by a continued slit, and so flexible as to be conveniently doubled or bent, in a greater or less degree, while the secondary or included tube is in the act of absorption. This secondary or included tube appears to consist of fine parallel linear parts, forming, by their junction or juxtaposition, a firm, yet exquisitely fine, sucker, which is forced into the skin of the animal attacked by the insect. The swelling which takes place after the bite, must be supposed to be owing to some acrimonious fluid injected into the punctured part, and which may cause the blood to flow with greater facility into the proboscis, during the time that organ is employed.

[Swinton. Phil. Trans. Shaw,

SECTION XII.

Ichneumon.

Ichneumon.-LINN.

THE animals of this genus provide for the support of their offspring in a manner highly extraordinary; depositing their eggs in the bodies of other insects, and generally in those of caterpillars. For this purpose the female ichneumon, selecting her victim, and fastening upon it, pierces its skin with her abdominal tube, and introduces her eggs beneath the surface. In vain the tormented animal endeavours to evade this cruel operation: the ichneumon maintains her hold, nor ceases till she has discharged her whole stock. These eggs in a few days hatch, and the young larves, which resemble minute white maggots, nourish themselves with the juices of the unfortunate animal, which however continues to move about and feed till near the time of its change to chrysalis; when the young brood of Ichneumon-larvæ creep out, by perforating the skin in various places, and each spiuning itself up in a small oval silken case, changes into chrysalis; the whole number forming a groupe on the shrivelled body of the caterpillar which had afforded them nourishment; and, after a certain period, emerge in the state of complete Ichneumons. One of the most familiar examples of this process, is afforded by the well-known caterpillar of the common white or cabbage butterfly; which, in the autumnal season, may be frequently observed to creep up some wall, or other convenient surface, in order to undergo its own change into chrysalis; but, in the space of a day or two, a numerous tribe of small maggots will be seen to emerge from it, and immediately proceed to envelop themselves in distinct yellow silken cases; the whole forming a groupe around the caterpillar. The ichneumons proceeding from these are the species called by Linnæus ichneumon glomeratus their colour is black, with yellow legs: they usually make their appearance in about three weeks from the time of their spinning themselves up. Other small species of Ichneumon pierce the skins of newly changed chrysalites of butterflies and moths, in which their larves remain during their own incomplete state; as the ichneumon puparum of Linnæus, a very small species, of a gilded