Homes Without Hands: Being a Description of the Habitations of Animals, Classed According to Their Principle of Construction - Page 37

One of the wood-boring bees is especially worthy of notice, because some of its habits were remarked a century ago by Gilbert White, who did not know its name, but chronicled its method of obtaining padding for the nest. We will call it the HOOP-SHAVER (Anthidium manicatum). It is one of the summer insects, seldom appearing before the beginning of July, and is a rather stout-bodied insect, grayish-black, with yellow lines along the sides of the abdomen. The last segment of the male is notable for its termination in five teeth. Its length is rather under half an inch, and it is a very remarkable fact that, contrary to general usage among insects, the male is larger than the female.

This bee seldom takes the trouble of making its own burrow, but takes advantage of the deserted tunnel of some other insect, such as the musk-beetle or the goat moth. When she has selected a fitting home, she enlarges it slightly at the end, and then goes in search of soft vegetable fibre wherewith to line it. The mode of procuring the fibre is thus mentioned by White. "There is a sort of wild bee frequenting the garden campion for the sake of its tomentum, which probably it turns to some purpose in the business of nidification. It is very pleasant to see with what address it strips off the pubes, running from the top to the bottom of a branch, and shaving it bare with the dexterity of a hoop-shaver. When it has got a vast bundle, almost as large as itself, it flies away, holding it secure between its chin and its fore legs."

After performing this part of her duty, she makes a number of cells, using the same material, together with some glutinous substance, places an egg in each cell, and then leaves them. When the larvæ have obtained their full dimensions, they spin separate cocoons within the cells, and in the following summer the perfect insects make their appearance.

IF the reader will visit any fir wood, and look out for the dying and dead trees which are sure to be found in such places, he will probably see that many of them are pierced with round holes, large enough to admit an ordinary quill. These are the

The mode in which the Sirex carries on its operations is simple enough.

With the long and powerful ovipositor the mother insect introduces her eggs into the tree, and there leaves them to be hatched. As soon as it has burst from the egg the young grub begins to burrow into the tree, and to traverse it in all directions, feeding upon the substance of the wood, and drilling holes of a tolerably regular form. Toward the end of its larval existence it works its way to the exterior of the trunk, and there awaits its final change, so that when it assumes its perfect form it has only to push itself out of the hole, and so finds itself in the wide world. The insects may often be seen on the trunks of the trees, clinging to the bark close to the hole out of which they have emerged. Sawyers frequently destroy the grubs while they are cutting trees into planks, but as many of the larvæ escape the saw, they remain in the boards, and afterward emerge in houses, to the great consternation of the inmates. Should such a circumstance occur in the house of any reader of this book, he may at once infer that the wood from which the insect escaped was not properly seasoned. I have known the Sirex to be so numerous that it has fairly driven the inhabitants out of their rooms, for it has a very ferocious appearance, and, on account of its long ovipositor, is always thought to be armed with a venomous sting of peculiar potency.

Two species of Sirex inhabit this country. In general appearance they are very similar to each other, but the species just mentioned is nearly twice the size of its relative. They inhabit similar localities, and I have now before me a piece of a fir-tree in which are the holes of both species. These insects are not only interesting in their habits, but they furnish many beautiful objects for the microscopist.

In the accompanying illustration, we have three excellent examples of wood-boring insects. In the centre of the drawing is seen a portion of a tunnel, which is completely hollowed out, and divided into cells. This is the dwelling which is constructed by the splendid South African CARPENTER BEE (Xylocopa Capensis), a wood-borer of great power. She sets about her work in a curiously systematic manner, each action being exactly calculated, nothing left to chance, and all useless labor saved.

When the insect has fixed upon a piece of wood which suits her purpose, usually the trunk or branch of a dead tree, an old post, or a piece of wooden railing, she bores a circular hole about an inch and a half in length, and large enough to permit her to pass. Suddenly, she turns at an angle, and drives her tunnel parallel to the grain of the wood, and makes a burrow of several inches in length. None of the chips and fragments are wasted, but are carried aside and carefully stored up in some secure place, sheltered from the action of the wind.

The tunnel having now been completed, the industrious insect seeks rest in change of employment, and sets off in search of honey and pollen. With these materials she makes a little heap at the bottom of the tunnel, and deposits an egg upon the food which she has so carefully stored.

Having now shown her powers as a burrower and a purveyor, she exhibits her skill as a builder, and proceeds to construct, above the inclosed egg, a ceiling, which shall be also the floor of another cell. For this purpose, she goes off to her store of chips, and fixes them in a ring above the heap of pollen, cementing them together with a glutinous substance, which is probably secreted by herself. A second ring is then placed inside the first, and in this manner the insect proceeds until she has made a nearly flat ceiling of concentric rings. This ceiling bears some resemblance to the operculum of the common water snail. The reader will probably remember, that the ceilings constructed by the ant are made on similar principles. The thickness of each ceiling is about equal to that of a penny.

The number of cells is extremely variable, but on the average each tunnel contains seven or eight, and the insect certainly makes more than one tunnel. As each tunnel generally exceeds a foot in length, and the diameter is large enough to admit the passage of the wide-bodied insect who makes it, the amount of labor performed by the bee is truly wonderful. The jaws are the only boring instruments used, and though they are strong and sharp, they scarcely seem to be adequate to the work for which they are destined.

In the illustration, the upper part of one of these tunnels is shown, and in the two uppermost cells the egg has not been hatched. In the lower cells the young larva is given, in order to show the attitude in which it passes its early life. When all is completed the entrance is closed, with a barrier formed of the same substance and in the same manner as the ceilings.

As far as is yet known, no member of the genus Xylocopa is indigenous to this country.

Among the insect nests in the British Museum is a fine example of the burrow made by a Brazilian member of this genus, Xylocopa grisescens. It is a very large insect, and the hole is so wide that it will easily admit a man's thumb. There is in the same case a nest of a curious Australian bee, Lestis bombylans. The insect is very like a humble-bee, but remarkable for the bright steel-blue of its body, and the absence of hair. The burrow runs through a branch, but is not in the centre, having at least three fourths of the thickness of the wood on one side, and only one fourth on the other. All the cells are filled with bee-bread.

In the upper right-hand corner of the illustration may be seen a curious-looking insect, having its abdomen at the end of a very long footstalk. This is the Pelopœus spirifer, an insect belonging to the family Sphegidæ. It is rather a pretty insect, though formidable in aspect, the body and abdomen being black, and the limbs and long footstalk bright yellow. The genus Pelopœus is widely spread over the hot parts of the world, and its members are rather diverse in their habits. Many of them are notable builders, using mud as the material with which they make their nest, and will therefore be described under the head of Builders. The present species, however, takes rank as a wood-burrower, and, as may be seen from the illustration, makes a long tunnel inside a branch, and divides it into cells. True to the instinct which seems common to its kind, the Pelopœus does not make the divisions of wood-chips, as is the case with the Xylocopa, but uses mud for the purpose. Instead of storing her cells with bee-bread, she captures spiders, and with their bodies supplies her future young with food, just as is the case with so many earth-boring hymenoptera.

THE last figure in the illustration represents one of the wood-boring beetles, and is given in order to show the curious effect which is produced by its tunnels. The beetle mostly prefers the twigs of the aspen as a home, and its presence can always be detected by the swollen aspect of the injured twig, looking as if the tree were affected with gout. This is a British insect, Saperda populnea by name, and in some places it is extremely injurious to the aspen and poplar, always choosing the second or third year's wood, and effectually spoiling its farther growth. The larva has a small, flat head, a suddenly-enlarged thorax, and a body tapering regularly to the tail.

Of this genus there are many species, each taking its own tree. Saperda cylindrica, for example, prefers the pear, plum, and other stone fruit, though it is sometimes found in the nut. It always completes its larval existence in the centre of the stem. Another species prefers the oak. It is fortunate for the owners of woods that the Saperda is greatly persecuted by a parasitic fly belonging to the genus Tachina, and that its numbers are much thinned by the dipterous usurper.

THE Lepidoptera number among their ranks some of the most destructive wood-boring insects that inhabit this country.

There is, perhaps, no insect which makes so large or so ramified a burrow as the common GOAT MOTH (Cossus ligniperda). This insect is far more plentiful than is generally supposed, but as in its larval and pupal state it is deeply buried in some tree-trunk, and in its perfect condition seldom ventures to fly by day, not one in a thousand is ever seen by the eye of man. This moth breeds in several trees, such as the willow, the oak, and the poplar, the first-mentioned tree seeming to be its chief favorite. Kent is one of the counties wherein this moth is found in greatest profusion, and in the fields round my house there is scarcely a willow of any size which has escaped the ravages of the Goat Moth caterpillar.

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