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

THERE is another gall, very common in England, which is found upon the oak, and which is generally thought, by persons who are unacquainted with botany or entomology, to be the buds which naturally grow upon the tree.

In these curious galls, the excrescences with which they are covered take the form of leaves instead of hairs, as is the case with the bedeguar and many other galls. These bud-like objects may be found on the young twigs, and may be easily recognized by their shape, which somewhat resembles that of a pine-apple, and the curious manner in which their leafy covering lies regularly over them, like the tiles upon an ornamental roof. The size of the gall is rather variable, but is, on an average, about as large as an ordinary hazel-nut.

The gall is so wonderfully bud-like that I have known the two objects to be confounded—the immature acorns in their cups to be carried off as galls, while the real galls were left on the tree. The incipient naturalist who made the mistake kept the buds for some eighteen months, and was sadly disappointed to find that no insects were produced from them.

The insect whose acrid injection produces this curious effect upon the tree is rather larger than the leaf-gall insect, and is of more slender proportions. It has been suggested that the object of the leafy or hairy covering is, that the insect, which remains in the gall throughout the winter, should have a warm house by which it may be protected from the chilling frost, as well as from the wind and rain.

IF the reader will again refer to the illustration, he will see that from the same branch on which the Cynips Kollari has formed so many galls depend two slender threads supporting one or two globular objects. These are popularly called CURRANT GALLS, because they look very much like bunches of currants from which the greater part of the fruit has been removed. Their color, too, is another reason for giving them this name, as they are sometimes scarlet, resembling red currants, and sometimes pale cream-color, thus imitating the white variety.

These galls are placed upon the catkins of the oak, which are forced to give all their juices to the increase of the gall, instead of employing them on their own development. Some authors think that the insect which forms them is a distinct species, while others think that the galls are the production of the same insect which forms the leaf gall, the punctures being made in the stalk of the catkin and not in the nervure of the leaf.

That this supposition may be correct is evident from the fact that the same insect which forms the oak apples does also deposit its eggs in the root of the same tree, causing large excrescences to spring therefrom, each excrescence being filled with insects. I have often obtained these root-galls, several of which are now before me, some having been cut open, in order to show the numerous cells with which they are filled, and others left untouched, in order to exhibit the form of the exterior. Being nourished by the juices of the root, they partake of the sombre hues which characterize the part of the tree from which they spring, and do not display any of the colors which are seen on the oak apples which spring from the twigs.

There are, however, distinct species of gall insects which pierce the roots of the oak-tree. One of them is termed Cynips aptera, and makes a pear-shaped gall about one third of an inch in diameter. Each gall contains a single insect, and a number of the galls are often found attached by their narrow end to the root-twigs of the tree, something like a bunch of nuts on a branch. There is another insect which is termed Cynips quercus-radicis, which forms a many-chambered gall of enormous size, containing a small army of insects. Mr. Westcott mentions that one of these galls in his possession was five inches long, one inch and a quarter wide, and produced eleven hundred insects, so that the entire number was probably fourteen or fifteen hundred.

No one who is accustomed to notice the objects which immediately surround him can have failed to observe the curious little galls which stud the leaves of several trees, and which are appropriately called SPANGLE GALLS, because they are as circular, and nearly as flat, as metallic spangles.

These objects had been observed for many years, but no one knew precisely whether their growth was due to animal or vegetable agency. That their substance was vegetable was a fact easily settled, but some botanists thought that they were merely a kind of fungus or lichen, while others supposed that they were the work of some parasitic insect.

When closely examined, these “spangles” are seen to be disks, very nearly, but not quite flat, fastened to the leaf by a very small and short central foot-stalk. Réaumur set at rest the question of their origin by discovering beneath each of them the larva of some minute insect, but he could not ascertain the insect into which the larva would in process of time be developed. The task of rearing the perfect insect from the gall is exceedingly difficult, the minuteness of the species and the peculiar manner in which the development takes place being two obstacles which require a vast expenditure of care and patience before they can be overcome.

Supposing a branch containing a number of infested leaves to be placed in water and surrounded with gauze, it will die in a week or two, and yet there will be no sign of an insect. If the branch be kept until the winter has fully set in, the desired insects will still be absent, and the experimenter will probably think that his trouble has been thrown away. The real fact is, that the little insects are not developed until the spring of the following year, and that they pass through their stages of the pupal and perfect forms after the leaves have fallen, and while they are still lying on the ground.

Mr. F. Smith, who has given so much time and research to the history of the Hymenoptera, has discovered the insect that inhabited the galls to be Cynips longipennis, and has remarked that the perfect insects do not make their appearance until the month of March.

WE now pass from the British galls to those which are found in various other countries. A few of the more interesting examples are figured in the accompanying illustration.

Should the reader have the curiosity to examine for himself the structure of the British galls (as I trust he will do), he will find that when he cuts a juicy specimen, such as that of the leaf gall, his fingers will presently be stained with purple-black. He may wash his hands as much as he likes, but he will not wash away the stain, which soon looks as if it had been produced by spilling ink on the hands. There is reason for such an appearance, inasmuch as the staining liquid is really ink, though of a paler hue than that which is used for writing. A little lemon-juice will soon discharge the color, and then the soap and water will remove the last remnants of the stain.

Ink is made by mixing a solution of the sulphate of iron (properly called green vitriol or copperas) with a decoction of certain oak galls. Perhaps I may mention that a "decoction" signifies water in which any substance has been submitted to boiling heat, but not dissolved. Tea, for example, is, when properly made, a decoction of the leaf, though when made with hot, but not boiling water, it has no right to the name. The solution of copperas is only pale green, and that of the gall is nearly colorless, although when mixed they become deeply black. The old practical joke of forcing a dupe to stain his hands and face black depended on the knowledge of these properties.

Ink Galls. Hungarian Gall.

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Dead Sea Apple. Galls of Cynips polycera.

Before the victim went to wash his hands, some of the decoction of galls was poured into the water, while the towel with which he was supplied had been damped with the copperas solution and then dried. The consequence of this combination was, that although the hands and face might be washed perfectly clean, yet, as soon as they were dried with the prepared towel, the union of the two substances produced ink, and both hands and face were deeply stained.

Now when a gall is cut with a knife, the slightly acid juice acts upon the steel, and so a kind of ink is produced, which is pale, but still a veritable ink. There is a well-known method of secret writing which depends on this property of iron and tannin, the principle contained in the galls.

A quill pen is dipped in the solution of copperas, and the required message is written, usually between the lines or among the words of a letter on unimportant subjects, so as to avoid the suspicions which would be aroused by a sheet of blank paper. The almost colorless solution leaves no mark, and the letter passes without comment until it reaches the person who is in the secret. He pours some decoction of galls into a wide and flat vessel, and warily dips the letter into it, so as to wet it; or he saturates a cloth with the decoction, and lays the letter upon it. The tannin then acts upon the solution of iron, ink is formed by their combination, and the formerly invisible words immediately become plain and legible.

Foreign Galls.

A decoction of oak bark would make ink, though of inferior quality, and so would tea, inasmuch as the tea-leaf contains a large amount of tannin. In fact, whenever the ink in the bottle becomes thick, it can always be restored by adding to it a little strong tea, which not only gives the requisite liquidity, but does so without affecting the blackness, which would probably be the case if simple water were added.

The two principal ingredients of the ink which is in common use are sulphate of iron and the galls of a species of oak called Quercus infectoria, which grows in large quantities in the Levant. They are technically termed Aleppo galls, and are divided into several classes, according to their value. Besides these two ingredients a little gum is added, in order to give consistency, and a very little corrosive sublimate or creosote, to prevent the growth of mould. The proportions are generally six ounces of pounded galls, four ounces of copperas, and four ounces of gum-arabic to six pints of water.

In the upper left-hand corner of the illustration two of these galls are seen upon a branch of the oak.

They are necessarily much reduced in size, their ordinary dimensions being about equal to those of Cynips Kollari. For the purposes of trade they are divided into black, blue, green, and white galls. The last-mentioned class of galls includes those from which the insects have escaped, and which are consequently weakened in astringency. They are so called because they assume a paler hue than the three first classes, in which the insect still remains. In shape, the ink gall is nearly spherical, with a slight tendency to a pear-like form, and their exterior is defended by a few short, stout, and rather sharp prickles.

I can not but think that the gall insect affords a proof that the most insignificant objects of creation have their uses, provided that we could only discover them. Nature is a vast treasure-house, or rather a city of treasure-houses, very few of which have been unlocked because no one has found the keys. No one, indeed, is likely to do so as long as he chooses to despise "little things," and if the only acknowledged benefit conferred on mankind by the insect tribes had been the ink gall, it is a boon so great that every insect ought to deserve our respect as the possible donor of some similar aid to civilization at present unknown.