tion, and, by means of little paddles on their hinder part, to plunge to the bottom. In the course of a few days they are transformed into perfect Gnats. The chrysalids swell at the head, and the flies burst from their enclosure. If, at the instant of the change, a breeze springs up, it proves to them a dreadful hurricane, as the water gets into their case, from which they are not yet perfectly loosened; this immediately sinks, and they are drowned.

rays

If Gnats were not devoured by fish, water-fowl, swallows, and other animals, the air would often, from their immense multitudes, become darkened: a few instances have occurred in which this has been the case. In July, August, and September, 1776, at Oxford, Gnats were sometimes seen, towards the evening, in such myriads as literally to darken the of the sun; and their repeated bites swelled the exposed parts of the body to an enormous size, and caused the most troublesome and unpleasant sensations. Mr. Swinton, who has given an account of them in the Philosophical Transactions, has stated that one evening, about half an hour before sun-set, he was in the garden of Wadham College, when these insects were observed in numbers almost unexampled. Six distinct columns were observed to ascend from the tops of six branches of an apple-tree in an adjoining garden. Two of these columns seemed perfectly erect, three of them were oblique, and one approached somewhat of a pyramidal form. The bodies of some of the Gnats were greatly distended with blood; one considerably larger than the rest, had as much blood expressed from it as besmeared a space three inches square. About thirty years before this period, many columns of Gnats were observed to rise from the top of the cathedral church of Salisbury. At a little distance, they had so great a resemblance to smoke, as, at first, to occasion an alarm that the church was on fire.

It is impossible to behold and not admire the beautiful structure of the proboscis, through which the Gnat

draws the juices that afford it nourishment. The naked eye is only able to discover a long and slender tube, containing five or six spicule of exquisite fineness. These spiculæ, introduced into the veins of animals, act like the suckers of a pump, and cause the blood to ascend. The insect injects a small quantity of liquid into the wound, by which the blood is made more fluid. The Gnat, as it sucks, swells, grows red, and does not quit its hold till it has gorged itself. The liquor it has injected causes a disagreeable itching, which may in some degree be removed by volatile alkali, or by immediately rubbing and washing the place with cold water.

Gnats are said sometimes to shine in the dark.

The Musqueto-fly is nothing more than a large variety of the Common Gnat. These insects are found in great abundance in the woody and marshy parts of all hot climates; and, during the short summer, throughout Lapland, Norway, and Finland, and other countries equally near the Pole.

It is the female only that bites and sucks the blood; and this operation is so severe, as to swell and blister the skin in a violent manner, and sometimes even to leave obstinate sores. Musquetoes are found in such swarms in the woods, that whoever enters them, is sure to have his face covered, and he is scarcely able to see his way before him. A swelling and disagreeable itching immediately follow the puncture, and these are succeeded by small white ulcers. Even gloves are not always found a protection against these troublesome insects.

The Laplanders, whilst employed in the woods, on the necessary business of cutting timber, are unable to take the refreshment of their meals; for their mouths, as soon as opened, would be filled with Musquetoes. If the wind happen to blow briskly, the animals disappear for the time; but no sooner is it again calm than they return, and crowd every place. They also dread

fully infest the cattle and rein-deer. When these return from the woods, they are found covered with Musquetoes; and, on the insects being swept from their backs and sides, their skins are red with blood.

The lowest class of people, in all the climates where Musquetoes abound, keep them out of their huts, during the day-time, by burning there a continual fire: the Laplander, when in bed, has a better contrivance to defend himself from their stings. He fixes a leather thong to the poles of his tent, this raises his canvass quilt to a proper height, so that its sides or edges touch the ground. Under this he creeps, and passes the night in security. When Mr. Acerbi and his friends arrived in a cottage in the village of Killare, in Lapland, the first favour the women conferred on them, was to light a fire, and fill the room so full of smoke, that it brought tears from their eyes. This was done to deliver them from the molestation of the Musquetoes; and, as a means of effectual prevention, they made a second fire, near the entrance of the apartment, to stop the fresh myriads, which would otherwise have rushed in upon them from without.

The buzzing of Musquetoes is so loud, as to disturb the rest of persons in the night, almost as much as would be done by their bite. The more opulent inhabitants of climates where these insects abound, usually sleep under nets of gauze or n.uslin.

OF THE HIPPOBOSCE, OR SPIDER-FLIES*. The Hippoboscæ form a connecting link betwixt the two-winged and the apterous insects. By some authors they have been denominated mouches araignées,

* The mouth is furnished with a short, cylindrical, straight, two-valved sucker; the valves of which are equal. The antennæ are filiform. The feet are armed with numerous claws; and the body is flat and hard.

or spider-flies, from a distant resemblance which some of them have to Spiders.

A few of the species are found in woods and marshy places; but the greater number of them infest the bodies either of quadrupeds or birds.

THE FOREST-FLY*.

In the neighbourhood of the New Forest, Hampshire, and in several other parts of England, these insects are extremely numerous during the summer season. They collect, sometimes in great numbers, upon the necks and shoulders, under the belly, on the interior part of the thighs, and under the tails of horses, where they run about with an oblique motion, and feed by sucking the blood of these animals through their proboscis. They adhere so firmly with their claws to the hair, that they cannot, without great difficulty, be driven away; and even if this happen to be done, they almost always return after a short flight. So hard and tough are their skins, that it is almost impossible, by crushing, to kill them; and the almost only effectual mode of destroying them is, to tear off their heads.

To all horses that are unaccustomed to their attacks, the Forest-flies are peculiarly obnoxious, nor is it until after a considerable lapse of time, that high-spirited and tender-skinned animals become reconciled to them.

In the production of their offspring these insects are very peculiar. Each female has but one egg at a time. This is extremely singular in its form and appearance, and, in size, is nearly as large as the belly of the paShe fastens it to the hairs of the horse, by a

rent.

* DESCRIPTION. The general colour of the Forest-fly is brown; the thorax varied with pale yellow, and the legs annulate with yellow and brown. The wings are obtuse: they cross each other and are hyaline, with a brown spot near the outer margin, The feet are furnished with four claws.

SYNONYMS. Hippobosca equina. Linn.-L'Hippobosque du Cheval. Cuvier.

gluey matter with which it is covered, and in some place where it is not liable to be rubbed off. To those persons who might be inclined to consider it impossible for so small an insect to produce from its body so large a substance, it may be observed, that the skin of the Forest-fly is like a bladder or purse, very tough, and capable of great expansion.

I have called the above-mentioned production, the egg of the Forest-fly, but in this particular I do not speak correctly; for it should appear, that the real egg is hatched within the body of the insect, where the larva also completes its growth, and that this substance is the pupa, enclosed in a kind of skin, which is so tough and strong, as to be capable of sheltering it from all injury. From its first extrusion it may be observed to have a slight movement, an alternate retracting and expanding of the skin, somewhat similar to the beating of the heart.

At one of the ends there is a kind of valve or cap, divided into two equal pieces. As soon as the insect becomes perfected, it pushes this open with its head, and issues forth.

Forest-flies are occasionally found upon cattle; and, in open countries, even upon dogs.

Apterous Insects*.

OF THE TERMES TRIBET.

The present tribe is arranged by Linnæus among the

* The Linnean_order Aptera, comprises all such insects as are destitute of wings in both sexes.

+ The mouth is furnished with two horny jaws, and has a