ANATOMY OF THE WOOD-PECKER.

season, the month, and often the very day recurs, when it is wanted. If chance has done this, infinite wisdom could not have done it better.

A variety of instances might be adduced to show with what admirable skill individuals of this tribe are formed for peculiar modes of life; but I shall mention only one, by way of confirming and illustrating the former remarks. The structure of the WOOD-PECKER is deserving of our notice. Its food is generally in or under the bark of trees. It has therefore feet and claws which enable it to fix itself upon the stems of trees of all dimensions, and in all positions, perpendicular, horizontal, or oblique, and to move along them without danger of falling. In order to this, two of its toes are disposed forward, and two backward. Its tail assists also in the pursuit of its food. Placing itself on the perpendicular stems of trees, it would be in danger of falling backwards; but the 'feathers of its tail are remarkably strong, which it places against the tree, and is by that means enabled to remain in the same position for a considerable time. "Their tongue," says Ray, speaking of these birds, "they can shoot forth to a very great length, ending in a sharp stiff bony rib, dented on each side; and at pleasure thrust it deep into the holes, clefts, and crannies of trees, to stab and draw out insects lurking there; as also into ant-hills, to strike and fetch out the ants

and their eggs. "" h Derham informs us, "that their

THE STRUCTURE OF INSECTS.

tongue encompasses part of the neck and head, the better to exert itself in length, and again to retract it into its cell." This member, by a curious apparatus of bones and muscles, the bird exerts with considerable force. As it makes its nest in holes in the stems of trees which it excavates for itself, it is necessary that its bill should be formed for such hard labour. It is so in fact. It is hard, strong, and made like a wedge; and a ridge runs along the top of it, which greatly adds to its strength. Various ends are to be accomplished;-and what a curious apparatus of means is provided, all the parts of which are most wisely adapted.

INSECTS.

j

Amongst those animals which are formed for living in or flying through the air, we may rank the various tribes of winged insects, the general structure of which I shall now consider.-Their form is suited to passing through the air. They are covered with a sort of horny or shelly substance, in the shape of

Derham's Physico-Theol.

j RAY supposed the various species of insects to be ten thousand. There are more than one thousand different species of beetles in Great Britain. St. Pierre says there are six thousand species of flies; and nearly eight hundred different butterflies.

WINGS OF INSECTS.

rings surrounding their bodies, which are in the stead of bones, to strengthen and preserve them in their proper shape. To these rings the muscles and other instruments of motion are attached. In these species which have no bones, but whose bodies consist of such a succession of rings curiously incased into each other, there is a power of contracting and dilating them; thus all the movements of this kind are performed. The head, in some species, changes its form every moment. It contracts or dilates, appears or disappears, at the pleasure of the animal. These motions are permitted by the flexibility of the members, or coverings of the head. In other species, the form of the head is permanent, owing to the hardness of the coverings, which are scaly or crustaceous, and approaches nearer to that of the more perfect animals.*

As perspiration is essential to the preservation of animal life, and so hard a substance will not admit of this process, insects are provided with holes on their sides, which serve at once for perspiration and breathing. Their bodies are covered all over with hairs, many of them are decked with the most beautiful appearances, which, when viewed through the microscope, surpass in splendour the finest works of art, set with the most costly jewels.

and

Their WINGS are supplied with slender bones, by which they are distended and strengthened; these

* See Smellie.

THE EYES OF INSECTS.

are covered with a fine membrane, in some like a net-work, as the dragon-fly; in others, adorned with beautiful feathers, as the butterfly. The wings of some are constantly extended; such insects are almost perpetually flying about.-Those of others are supplied with joints for folding them up close to their bodies. Insects of this description live principally upon the ground, where their wings are more exposed to danger, from which they are defended by another kind of wings (elytra) which serve not for flying, but merely for covering and defence. These elytra resemble leather, of a hard and solid nature, and are often of a beautiful colour, as in the lady-bird. Their outer surface is convex, to keep off wet; the inner surface is concave, fitted to the shape of their body, and the protuberance occasioned by the folding up of the wings. At first sight, indeed, these insects do not appear to have wings.

The ORGANS OF SIGHT, with which insects are endowed, are peculiar to themselves, but admirably adapted to their necessities. The external covering of their eyes is hard and transparent, like glass. They consist, for the most part, of one lens only; but in those of the butterfly, and many of the beetles, they are numerous. Pugett discovered upwards of seventeen thousand lenses in the cornea of a butterfly; and Leuwenhoek, eight hundred in a fly.'

1 See Entomology, in Encyclop. Brit.

EYES OF INSECTS LENTICULAR-ANTENNE.

"This lenticular power of the cornea (says Derham) supplies the place of the crystalline, if not of the vitreous humour too; there being neither of those humours that I could ever find: but instead of humours and tunics, I imagine that every lens of the cornea has a distinct branch of the optic nerve ministering to it, and rendering it as so many distinct eyes.

Smellie remarks that no other animals but the insect tribes have more than two eyes. Some of them have four, as the phalangium; others, as the spider and scorpion, have eight eyes. In a few insects, the eyes are smooth; in all the others, they are hemispherical, and consist of many thousand distinct lenses. The eyes are absolutely immoveable: but this defect is supplied by the vast number of · lenses, which, from the diversity of their positions, are capable of viewing objects in every direction. By the smallness and convexity of these lenses, which produce the same effect as the object glass of a microscope, insects are enabled to see bodies that are too minute to be perceived by the human eye.

Insects are supplied with ANTENNE, which grow on the fore-part of the head: each insect is provided with two; in some they are more numerous. They are a kind of horns, and are supplied with