When the specimen has dried, the hair must be dressed by brushing and combing it. If the white poison shows on the hair, take a sponge, and with either hot water or alcohol sponge off the surface of the hair, leaving all the unseen poison undisturbed. If your solution contains the proper amount of poison, and is thoroughly applied, I warrant that insects will never again touch that specimen, even though it should exist a thousand years.
It often happens that moths get into cases of birds, or mammals, or insects, which cannot be treated as above without damaging the specimens. In such an event there are several poisons of a volatile character which give off fumes so deadly that no insect can live in them. The best for this purpose is naphthaline crystals, exposed in the cases in little bags made of musquito-netting, used in abundant quantity, and left in the cases, which must of course be kept closed as tightly as possible. In insect collections each box should have a little cone of crystals,[12] as a standing menace to all would-be marauders. Liquid or crystal bisulphide of carbon, exposed in saucers on the bottom of a tightly closed case will also kill whatever living insects may be found therein; but it does not destroy eggs, and by the time it has evaporated another generation of destroyers may have been born, hungrier than the first.
A half-ounce bag of naphthaline crystals will last about three months. Mr. John B. Smith, who published in the "Proceedings of the Entomological Society of Washington," vol. i., No. 2, p. 113, a very interesting paper on "Museum Pests," found in treating some boxes of coleoptera that were infested with Trogoderma that both bisulphide of carbon and naphthaline killed all larvæ and imagoes, and held all the eggs in a dormant condition, even through the summer months, until the poison had all evaporated, when the eggs began to hatch.
At present naphthaline in the form of crystals has become the most popular of the various volatile poisons, and among ornithologists, mammalogists, and entomologists is very generally used. It prevents mould, destroys bacteria and schizomycetes; the salt is perfectly neutral, is not poisonous to man, and is cheap, costing only twenty-five cents per pound.
Poisoning Textile Fabrics and Skin Clothing.—Objects of this class can not be put through any liquid poison, for the reason that some would be made hard and stiff, some would lose their colors, and all would come out in bad shape generally. To meet the exigencies of such cases one alternative is to poison the atmosphere of an air-tight case with some of the volatile poisons already mentioned, and the other is to treat each article with some powerful liquid poison, applied as a fine spray with an ordinary atomizer of gutta-percha, which can be purchased for from one to two dollars. The immense collections of the department of ethnology in the National Museum have necessitated a great amount of poisoning in both these ways, especially the latter, which has the merit of being permanent. In the "Smithsonian Report for 1887," vol. ii., pp. 549-558, Mr. Walter Hough has published a very complete, lucid, and valuable paper on "The Preservation of Museum Specimens from Insects, and the Effects of Dampness," which every zoological conservator should read and hold for ready reference.
In spraying large objects Mr. Hough uses either a Shaw & Geary No. 2 air-compressor (cost, $15) or a four-nozzle gutta-percha atomizer ($2.50), and the spray is from the following solution:
| Saturated solution of arsenic acid and alcohol | 1 pint. |
| Strong carbolic acid | 25 drops. |
| Strychnine | 20 grains. |
| Alcohol (strong) | 1 quart. |
| Naphtha, crude or refined | 1 pint. |
For treating specimens of ordinary size with the concentrated fumes of bisulphide of carbon, the National Museum uses a galvanized sheet-iron tank 3 × 2 × 2 feet, which has around its upper edge a deep groove filled with water, into which the rim of the cover fits when the tank is closed. The centre of the cover contains an air-hole, which is also capable of being hermetically closed in the same way. This tank should be used in the open air, if possible, so that the fumes will not injure the health of the operator.
Poisoning Rugs.—It has long been a problem how to poison a fur rug to protect it from insects, and yet to keep out of it the dry mineral poisons which would be injurious to the health of the little ones, the dog, and the cat, who are "tenants in common" of the bear-skin on the floor. Mr. F.S. Webster has solved the difficulty by poisoning all his rugs on the inside with our old and valued friend, arsenical soap. It strikes into and through the skin, of course, and, contrary to previous expectations, it is by no means offensive, or even noticeable by odor in the finished rug.
Furs.—Even in Washington, the City of Moths, Mrs. Hornaday carried the family rugs and furs, and all woolen clothing, through eight summers, unscathed, by the liberal use of camphor gum alone. If the crumbled gum is sprinkled liberally into the folds of anything when it is being folded or rolled up, its protection against moths is assured.