The moths themselves are, in the winged state, small and well fitted for making their way through the most minute hole or chink, so that it is scarcely possible to exclude them by the closeness of a wardrobe or a cabinet.[BQ] If they cannot effect an entrance when a drawer is out, or a door open, they will contrive to glide through the key-hole; and if they once get in, it is no easy matter to dislodge or destroy them, for they are exceedingly agile, and escape out of sight in a moment. Moufet is of opinion that the ancients possessed an effectual method of preserving stuffs from the moth, because the robes of Servius Tullius were preserved up to the death of Sejanus, a period of more than five hundred years. On turning to Pliny to learn this secret, we find him relating that stuff laid upon a coffin will be ever after safe from moths; in the same way as a person once stung by a scorpion will never afterwards be stung by a bee, or a wasp, or a hornet! Rhasis, again, says that cantharides suspended in a house drive away moths; and he adds that they will not touch anything wrapped in a lion’s skin!—the poor little insects, says Réaumur, sarcastically, being probably in bodily fear of so terrible an animal.[BR] Such are the stories which fill the imagination even of philosophers, till real science entirely expels them.
The effluvium of camphor or turpentine, or fumigation by sulphur or chlorine, may sometimes kill them, when in the winged state, but this will have no effect upon their eggs, and seldom upon the caterpillars; for they wrap themselves up too closely to be easily reached by any agent except heat. This, when it can be conveniently applied, will be certain either to dislodge or to kill them. When the effluvium of turpentine, however, reaches the caterpillar, Bonnet says it falls into convulsions, becomes covered with livid blotches, and dies.[BS]
The mother insect takes care to deposit her eggs on or near such substances as she instinctively foreknows will be best adapted for the food of the young, taking care to distribute them so that there may be a plentiful supply and enough of room for each. We have found, for example, some of those caterpillars feeding upon the shreds of cloth used in training wall-fruit trees; but we never saw more than two caterpillars on one shred. This scattering of the eggs in many places renders the effects of the caterpillars more injurious, from their attacking many parts of a garment or a piece of stuff at the same time. (J. R.)
When one of the caterpillars of this family issues from the egg, its first care is to provide itself with a domicile, which indeed seems no less indispensable to it than food; for, like all caterpillars that feed under cover, it will not eat while it remains unprotected. Its mode of building is very similar to that which is employed by other caterpillars that make use of extraneous materials. The foundation or framework is made of silk secreted by itself, and into this it interweaves portions of the material upon which it feeds. It is said by Bingley, that "after having spun a fine coating of silk immediately around its body, it cuts the filaments of the wool or fur close by the thread of the cloth, or by the skin, with its teeth, which act in the manner of scissors, into convenient lengths, and applies the bits, one by one, with great dexterity, to the outside of its silken case."[BT] This statement, however, is erroneous, and inconsistent with the proceedings not only of the clothes-moth, but of every caterpillar that constructs a covering. None of these build from within outwards, but uniformly commence with the exterior wall, and finish by lining the interior with the finest materials. Réaumur, however, found that the newly-hatched caterpillars lived at first in a case of silk.
We have repeatedly witnessed the proceedings of these insects from the very foundation of their structures; and, at the moment of writing this, we turned out one from the carcase of an “old lady moth” (Mormo maura, Ochsenheim) in our cabinet, and placed it on a desk covered with green cloth, where it might find materials for constructing another dwelling. It wandered about for half a day before it began its operations; but it did not, as is asserted by Bonnet, and Kirby and Spence, “in moving from place to place, seem to be as much incommoded by the long hairs which surround it, as we are by walking amongst high grass,” nor, “accordingly, marching scythe in hand,” did it, “with its teeth, cut out a smooth road.”[BU] On contrary, it did not cut a single hair till it selected one for the foundation of its intended structure. This it cut very near the cloth, in order, we suppose, to have it as long as possible; and placed it on a line with its body. It then immediately cut another, and placing it parallel to the first, bound both together with a few threads of its own silk. The same process was repeated with other hairs, till the little creature had made a fabric of some thickness, and this it went on to extend till it was large enough to cover its body; which (as is usual with caterpillars) it employed as a model and measure for regulating its operations. We remarked that it made choice of longer hairs for the outside than for the parts of the interior, which it thought necessary to strengthen by fresh additions; but the chamber was ultimately finished by a fine and closely-woven tapestry of silk. We could see the progress of its work by looking into the opening at either of the ends; for at this stage of the structure the walls are quite opaque, and the insect concealed. It may be thus observed to turn round, by doubling itself and bringing its head where the tail had just been; of course, the interior is left wide enough for this purpose, and the centre, indeed, where it turns, is always wider than the extremities. (J. R.)
Cases, &c., of the Clothes-Moth (Tinea pellionella).—
a. Caterpillar feeding in a case, which has been
lengthened by ovals of different colours;
b. Case cut at the ends for experiment;
c. Case cut open by the insect for enlarging it;
d, e. The clothes-moths in their perfect state,
when, as they cease to eat, they do no further injury.
When the caterpillar increases in length, it takes care to add to the length of its house, by working in fresh hairs at either end; and if it be shifted to stuffs of different colours, it may be made to construct a party-coloured tissue, like a Scotch plaid. Réaumur cut off with scissors a portion at each end, to compel the insect to make up the deficiency. But the caterpillar increases in thickness as well as in length, so that, its first house becoming too narrow, it must either enlarge it, or build a new one. It prefers the former as less troublesome, and accomplishes its purpose “as dexterously,” says Bonnet, “as any tailor, and sets to work precisely as we should do, slitting the case on the two opposite sides, and then adroitly inserting between them two pieces of the requisite size. It does not, however, cut open the case from one end to the other at once; the sides would separate too far asunder, and the insect be left naked. It therefore first cuts each side about half-way down, beginning sometimes at the centre and sometimes at the end (Fig. c), and then, after having filled up the fissure, proceeds to cut the remaining half; so that, in fact, four enlargements are made, and four separate pieces inserted. The colour of the case is always the same as that of the stuff from which it is taken. Thus, if its original colour be blue, and the insect, previously to enlarging it, be put upon red cloth, the circles at the end, and two stripes down the middle, will be red.”[BV] Réaumur found that they cut these enlargements in no precise order, but sometimes continuously, and sometimes opposite each other, indifferently.
The same naturalist says he never knew one leave its old dwelling in order to build a new; though, when once ejected by force from its house, it would never enter it again, as some other species of caterpillars will do, but always preferred building another. We, on the contrary, have more than once seen them leave an old habitation. The very caterpillar, indeed, whose history we have above given, first took up its abode in a specimen of the ghost-moth (Hepialus humuli), where, finding few suitable materials for building, it had recourse to the cork of the drawer, with the chips of which it made a structure almost as warm as it would have done from wool. Whether it took offence at our disturbing it one day, or whether it did not find sufficient food in the body of the ghost-moth, we know not; but it left its cork house, and travelled about eighteen inches, selected “the old lady,” one of the largest insects in the drawer, and built a new apartment, composed partly of cork as before, and partly of bits clipt out of the moth’s wings. (J. R.)
We have seen these caterpillars form their habitations of every sort of insect, from a butterfly to a beetle; and the soft, feathery wings of moths answer their purpose very well: but when they fall in with such hard materials as the musk beetle (Cerambyx moschatus), or the large scolopendra of the West Indies, they find some difficulty in the building.