Dermestes.—The greatest enemy of the zoological collector and conservator, and one which is world-wide in its distribution, is a small beetle, one-third of an inch in length, commonly called the "bacon beetle." Its flight is rather feeble, but "it gets there just the same." The most common species, Dermestes lardarius, is of a dark, dirty-brown color, with a broad, transverse band of dull gray encircling the middle of the body. The imago is not of much consequence as a destroyer, but the larva, a nasty, hairy, brown-backed, and white-bellied abomination half an inch long, and with an appetite like a hog, is the incarnation of all that is pestiferous. A skull that has been "roughed out" and put away without poisoning will soon be literally swarming with Dermestes larvæ, and half-buried with the brown, powdery excrementation they leave behind. If the curator ever sees a fine, brown dust falling in little heaps out of any part of a mounted specimen, he may know that Dermestes larvæ are at work.
Not long ago the National Museum was visited by another species of the bacon beetle, Dermestes maculatus, a gray-colored variety, beside which his congener seemed harmless and inoffensive. Maculatus was an unmitigated terror. He disdained to graze modestly on the outside of a specimen, as did lardarius, but simply began to eat wherever he "lit," and went straight in to a depth of an inch or so, as if shot out of a gun. An unhappy stuffed monkey that once crossed the track of this little fiend had half a dozen neat round holes eaten through the dry skin of his side, and straight on into the hard tow filling for quite an inch. A gimlet could not have done the work half so well. The most ridiculous thing was that this insatiable little monster attacked a plaster cast, and bored it full of holes also! Fortunately for the National Museum, the stay of this highly interesting stranger was of brief duration. He came in 1885, and vanished that same year—so far as my observations went.
Moths.—Next in destructiveness are the tiny moths, of which four species are to be fought in the museum and the household. These are the clothes moth (Tinea flavifrontella), the fur moth (T. pelionella), the carpet moth (T. tapetzella), and the grain moth (T. granella). The perfect moth is of course by preference a night-flying insect, and very seldom flies in the daytime except when disturbed. The imago is harmless, but the larva—a tiny, white worm no thicker than a pin, and about one-tenth of an inch in length—will soon shave the hair off an unpoisoned elk or deer head more smoothly than you could do it with the best razor ever made. Of course moth larvæ are most active and destructive during the breeding season—the warm months from May to October—but in warm rooms they sometimes keep at work all through the winter.
In one sense the moth is the zoologist's most dreaded foe, for the reason that its work is so subtle and unseen. Often the first intimation the victim has of the presence of his enemy is when dusting a favorite head he suddenly knocks off a section of hair half a foot square, exposing underneath the smooth, bare skin covered with fine gray dust. The larvæ of the moth attack birds and quadrupeds in one way only, that is by eating the roots of the hair or feathers, and the epidermis. Mounted heads of large ruminant animals are the particular prey of these abominable pests, because they cannot be protected by glass cases, and are seldom touched save with a feather duster.
In ethnological collections all the garments of skin and leather, and all the textile fabrics are subject to the attacks of the Tineids, as they also are to those of the species to be noticed next.
Anthrenus.—Although I have seen this "buffalo bug" try hard to make an impression on mounted mammals, I have not yet seen it do harm except to furs and leather or woolen garments. The adult buffalo bug (Anthrenus lepidus) is a tiny, round, brown beetle, with white spots on its elytra, and, as usual, it is the larvæ that do the mischief.
Symptoms of the Presence of Insect Pests.—Whenever little heaps of brown dust are seen accumulating here and there on a pedestal underneath a mounted specimen, know that dermestes are actively at work somewhere above. Sometimes the larvæ will even show themselves on the hair, which means a bad case.
If a perfect moth is seen flying in a case, or resting on a specimen, search at once for the larvæ. The best way to do this is to go over a specimen with a rough brush, or a comb, to see if the hair pulls out at any point. If a tuft of hair gives way at its roots, and you see a bare spot underneath, it means moth larvæ.
Poisoning.—Let us take first the case of a mounted specimen which is known to be infested with the larvæ of either Dermestes or Tineids. It must be treated thoroughly all over with a powerful poison, not only to kill the insects already there, but to poison any larvæ that may be hatched hereafter and seek to attack it.
If possible, remove the specimen from its pedestal, and beat out of it whatever dust it may contain. Procure a quantity of alcohol sufficient when diluted with fifty per cent of water to completely saturate the hair (or feathers) of the specimen, and dissolve in it some corrosive sublimate—about one ounce to every three pints of the liquid. The point to strive for in making up such a solution is to make it as strong with the corrosive sublimate as it can be without leaving on dark hair a gray (or white) deposit when the liquid has evaporated. In practice I always mix the liquid, and then test it with a tuft of black or brown hair. If the deposit left is quite apparent to the eye, a little more alcohol and water must be added. The principle of the process is simply this: The alcohol, being at once very penetrating and very volatile, and also capable of combining chemically with the corrosive sublimate, is used as a vehicle for the distribution of the poison. The poison is carried to the roots of the hair and left there as a deposit when the liquid evaporates. In Chapter XVIII. the method of applying this solution is described. Arsenic water, also described there, is equally good, and any intelligent person can make up either solution and apply it successfully without the slightest difficulty.