THE history of an insect, like the history of a man, is an account of life from first to last, from birth to death. Insects are so constituted, that the history of an individual is the history of its race: climate, season or circumstance exercises but little power of creating differences among them; a bee is as essentially a bee, and a butterfly a butterfly, at the equator as at the poles; and in either situation performs the same acts. Insects of all kinds, and in all situations, resemble each other in the following particulars:-they proceed from the parent as eggs; the eggs are hatched and become grubs, in which state they eat,

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increase rapidly in size, and are invariably without wings; the grubs, when full grown, become for a time motionless; their skin opens, and from it comes forth the perfect insect, which has four wings, and does not increase in size. In a very great number of insects the grub changes its skin, and completely alters its form, when it becomes motionless; indeed, almost as great a transformation takes place as on its final change to a perfect insect; when this is the case, the animal, in its motionless state, is called a chrysalis. Thus we have four stages in the life of an insect,―four states which it is necessary thoroughly to understand; the egg (ovum), which is motionless, and apparently lifeless; the grub (larva), which is active, but without wings, voracious, and grows rapidly; the chrysalis (pupa), which is quite motionless, and does not occur in all insects; the perfect insect (imago), which is active, has wings, does not grow, and which, by laying eggs, perpetuates its kind. The names egg, larva, pupa, and imago, are the terms generally employed in descriptions; the three last answer equally well for Latin and English, but it must be borne in mind that the words, grub, maggot and caterpillar, are synonymous with the term larva; and perfect insect, fly, &c., are synonymous with the term imago; and the English and Latin words are used in English descriptions almost indifferently. These transformations, often spoken of as the metamorphosis of insects, are in reality nothing more than a continual casting of the outer skin; the larva often casts its skin four or five times, without any very remarkable change of form; every casting of the skin is a step towards arriving at ultimate perfection. In every insect the skin must be cast a certain number of times, and the last casting brings it to maturity.

On account of their small size, it is difficult to find common examples of the eggs of insects; those laid on meat by

the blue-bottle fly must be known to many; the silk-worm's eggs again are not unknown; but the generality of insects' eggs are so concealed, and so little conspicuous, that they are found with difficulty. Examples of larvæ are numerous; the maggots found in wasps' nests and used in fishing, -the maggots in apples and nuts,—the maggots in cheese, and in decaying substances, and the caterpillars which devour our cabbages, and those which spin webs on our apple, pear, and plum trees, are familiar to us all: these are insects in the larva state. The pupa state is more difficult to find, because insects generally crawl away into crevices or hide themselves underground, before changing to this state; an angular pupa, of a green colour, with small black spots, which produces a common white butterfly, may, however, be frequently seen on palings and garden walls, and the smooth brown pupa of moths are continually dug up in gardens. The imago, or perfect state, is exemplified in butterflies, moths, gnats, flies, wasps, bees, ants, beetles, grasshoppers, earwigs, cockroaches, bugs, fleas, may-flies, and dragon-flies. All descriptions of insects in scientific works relate to the imago state, unless the contrary is distinctly expressed.

The mode in which the life of an insect is passed, differs very widely in the various states of its existence: it often happens that the larva inhabits the water and the imago the air; sometimes the larva inhabits the water, the pupa inhabits the earth, and the imago returns to the water. The following brief histories will in some degree exemplify this.

History of the Simulia.* -The eggs of the Simulia or sandfly (sometimes also called the mosquito), appear to be at present unknown; there is, however, little doubt, that like those of other gnats, they are deposited on the surface

* Authority;-M. Fries, in Entomologisches Archives.'

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of the water, and in that situation are hatched by the warmth of the sun combined with the moisture of the water. larva is found on the stems of water-plants (Phellandrium, &c.), on those portions which are always covered by the water it is long, cylindrical, considerably thickened posteriorly, and nearly transparent; its head is distinctly separated from the body, and is of an oblong form; it has four jaws moving horizontally, each bifid at the tip, and two little horns in the usual place of antennæ, inserted in the front of the head, rather towards each side; each of these is composed of two joints, the first or basal joint stout, the second or apical one, divided into many rays, which fold back on the first joint: there are two very small eyes on each side of the head. The body of the larva is divided into twelve segments, besides the head; of these, the second is incrassated, and furnished below with a retractile conical foot; the last segment is very minute, and furnished with two small prehensile feet: the air-tubes, so very plainly seen in other aquatic larvæ, are totally wanting; neither is there the least appearance of spiracles or breathing-holes in the sides.

The motion of the larva in the water is tolerably brisk; but on any object coming in contact with it, it instantly becomes motionless, attaches itself by the anterior prehensile foot, and remains for a long time perfectly still and immovable. When it moves from one place to another, its progression is undulating, somewhat like that of a leech, being performed in this manner:-the anterior foot is firmly attached to some object, then the posterior pair of feet are brought up to it, the back arching up during the operation; the anterior foot then releases its hold; the body is again elongated, the foot attached further on, and the posterior feet again brought up to it. The food of the larva is unknown: when full grown, it spins a little silken sheath, in

shape like a watch-pocket, which is attached to the plant