Homes Without Hands: Being a Description of the Habitations of Animals, Classed According to Their Principle of Construction - Page 36

The larva of the Musk Beetle is a mighty borer, making holes into which an ordinary drawing-pencil could be passed. Old and decaying willow-trees are its favorite resort, and in some places the willows are positively riddled with the burrows. If such a tree be sawn open longitudinally, a curious scene is presented to the spectator. In some spots, the interior is hollowed out by nearly parallel burrows, until it looks as if it had been tunneled by the ship-worm, while sections are made of burrows that turn suddenly aside, or gradually diverge toward the yet uneaten parts of the timber. In some of the holes will be found the long white grubs, in others the pupa may be seen lying quiescent, while a perfect beetle or two may possibly be discovered near the entrance of the holes. Nor are the Musk Beetles the only tenants of the tree, for there is generally an assemblage of wood-lice, centipedes, and other dark-loving creatures, which have crawled into the deserted holes, and taken up their abode within the tree.

If the reader will refer to the accompanying illustration, he will see that in the upper right-hand corner is represented a beetle

Rhagium, etc.

within a curiously-woven cell. This beetle belongs to the genus Rhagium. As long as the insect remains in its larval condition, it differs in little from the wood-boring larva. When, however, it is about to change into the pupal state, it makes a beautifully worked cocoon in which it spends the time which intervenes between the change into the pupa and that into the perfect insect. The cocoon is made of woody fibres, which the larva bites and tears away, and the hollow in which the cocoon rests is usually in the bark. The fibres are rather long and narrow, as may be seen by reference to the illustration, which represents the cocoon and insect of the natural size. As the woody fibres are of a pale-straw color, the cocoon presents an agreeable contrast to the sombre hues of the bark in which it is bedded. When the insect has attained its perfect form, its first care is to escape from the dwelling which has served it so well through its long period of helplessness; and by means of the sharp and powerful jaws with which it is furnished, it gnaws a hole through the side of the cocoon and so escapes into the open air. In the illustration, the beetle is represented in the act of making its way through the cocoon.

THE magnificent insect which is known to entomologists as the HARLEQUIN BEETLE (Acrocinus longimanus) also belongs to the wood-burrowers, and in the British Museum may be seen a piece of a tree in which the beetle is still lying, its enormously long limbs packed up into a very small compass. Exotic wood-burrowing beetles are very plentiful, and there is no doubt that several rare or doubtful British species have been introduced as grubs within foreign timber, and that they have made their way out after importation. The Docks are celebrated for the arrival of such distinguished strangers, and a fine collection of exotic beetles has been made by searching the cargoes of timber, after they have been discharged from the ships in which they were brought over the sea.

WE now come to the wood-boring bees, the name of which is legion, and a few examples of which will be now described and figured.

Immediately below the cocoon of the Rhagium may be seen a tunneled branch, containing two curiously-formed cells. These cells are made of rose-leaves, and are the work of the ROSE-CUTTER BEE (Megachile Willoughbiella), or WILLOW BEE, as it is often called, because its burrows are so frequently made in decaying willow-trees. This species is very common in most parts of England, and is therefore a good example of the wood-boring bees. The method by which the nests are made is very curious. After the insect has bored a hole of suitable dimensions in some old tree, she sets off in search of materials for the cells, and mostly betakes herself to a rose-bush, or laburnum-tree. She then examines one leaf after another, and having fixed on one to her mind, she settles upon it, clinging to its edge with her feet, and then, using her feet as one leg of a pair of compasses, and her jaws as the other, she quickly cuts out a nearly semicircular piece of leaf. As she supports herself by clinging to the very piece of leaf which she cuts, she would fall to the ground, when the leaf was severed, did she not take the precaution of balancing on her wings for a few moments before making the last cut. As soon as the portion of leaf is severed, she flies away with it to her burrow, and then arranges it after a truly curious fashion.

Bending each leaf into a curved form, she presses them successively into the burrow in such a manner that they fit into one another, and form a small thimble-shaped cell. At the bottom of the cell she places an egg and some bee-bread, this substance being composed of pollen mixed with honey, and then sets to work upon another cell; and in this manner she proceeds until she has made a series of cells, some two inches in length. When the cells are first made, the natural elasticity of the leaf renders them firm, and as they become dry and stiff in a few days, they are then so strong that they can be removed from the burrow, and handled without breaking.

There is another bee allied to this genus, that employs the petals of the scarlet poppy for this purpose, but unfortunately it is not a native of England. Another species of burrowing bee, Megachile centuncularis, seems rather capricious in its choice of burrows, at one time making its tunnel into an old post or decaying tree, at another into the mortar of old walls, at another into the ground. It is extremely variable in size, sometimes barely exceeding a quarter of an inch in length, and sometimes reaching twice that size. Mr. Smith mentions that this is perhaps the most widely distributed bee in the whole family of Apidæ, extending even as far northward as Hudson's Bay.

On the left hand of the same illustration may be seen a figure of one of the pith-boring bees, many species of which inhabit this country. This is the insect termed Hylæus dilatatus, and in order to assist the reader in identifying it, a figure of the insect itself is given on the right hand of the nest. Usually, the Hylæus is obliged to bore its way through the pith by sheer labor, but it will always avoid such a task if possible, and make its cells in a hollow already existing. Such has been the case with the nest from which the illustration was drawn, which was made in the hollow stalk of a hemlock. Here let me mention that all hollow stalks and twigs are likely localities for the nests of insects, and that toward the autumn a rich collection may often be made by the simple process of examining all such objects, and splitting them carefully with a knife. Even the reeds and rushes of the river are apt to contain nests, some of them being exceedingly rare.

The particular species of Hylæus which is here figured is by no means common, appearing to be a very local insect, confined to certain spots, and seldom seen except in those favored localities. Very many species of pith-boring insects are known, most of them inhabiting the dry twigs of the bramble and garden rose. If at the cut end of a branch a round hole be found in the pith, the observer may be sure that a nest of some kind is within. Generally, on carefully laying the branch open, there appears a whole series of cells, one above the other, and in such a case, the cells which are farthest from the aperture always contain the larvæ of female insects, those nearest the entrance being the males.

Sometimes the nests which are found in the bramble contain the larvæ of Osmia leucomelana, a pretty little bee, scarcely more than a quarter of an inch in length, black in color, with a very glossy abdomen, and a white, downy look about the legs. Five or six cells are made in each branch, and the perfect insect appears about the month of June.

Other bees of this genus are extremely clever in saving themselves labor. Although they can dig industriously when obliged to do so, they will never exert this power without compulsion. The smaller species are very fond of making their cells inside straws, and a thatched roof often contains thousands of nests, which are unsuspected by man, and only discovered by the tomtits and other birds, whose keen eyes soon detect the hidden insect, and whose ready bills pull the straws out of the thatch, and pick the larvæ from their cells. Nail-holes in garden walls are often filled with cells, and so are the auger-holes in old rails and posts, from which the wooden pins have fallen.

Several species select localities even more remarkable, and make their nests in the empty shells of snails. The common banded snail is a favorite with these bees, and in the British Museum may be seen a whole series of such nests. The number of cells necessarily varies with the size of the snail-shell and the number of its whorls, but on the average four or five cells are found in each snail-shell. The process of forming the cells is very simple. First, the bee deposits a quantity of pollen and honey, then she places an egg upon the pollen, and then she makes a partition with vegetable fibres torn by her teeth and kneaded firmly together. Lastly, the whole opening of the cell is closed by a wall formed of clay, tiny bits of stick, and small stones, and then the bee goes off in search of another shell. These shells may often be found under hedges, in moss, hidden by grass, and on examination the nests of bees will frequently be seen in them.

In the Museum there is a beautiful example of ingenuity on the part of the builder. Instead of choosing the shell of the banded snail, she has taken that of the great garden snail, and filled it with her cells. Thus it is evident that the shell is too large for the formation of a single cell, and the little architect has, with the greatest ingenuity, evaded the difficulty by placing two cells side by side. When, however, the smaller whorls of the shell were filled, and the bee approached the opening of the shell, the space was too great even for the two cells placed side by side. This difficulty was, however, overcome as readily as the former, and instead of placing the cells perpendicularly, the bee laid them horizontally, and thus filled up the space.

When the Osmia burrows into wood, she sets to work in a very deliberate manner. "A bee," writes Mr. F. Smith, "is observed to alight on an upright post, or other wood suitable for its purposes. She commences the formation of her tunnel, not by excavating downward, as she would be incommoded with the dust and rubbish which she removes; no, she works upward, and so avoids such an inconvenience. When she has proceeded to the length required, she proceeds in a horizontal direction to the outside of the post, and then her operations are continued downward. She excavates a cell near the bottom of the tube, a second and a third, and so on to the required number. The larvæ when full fed have their heads turned upward. The bees which arrive at their perfect condition, or rather those which are first anxious to escape into day, are two or three in the upper cells—these are males; the females are usually ten or twelve days later. This is the history of every wood-boring bee which I have bred, and I have reared broods of nearly every species indigenous to this country."

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