"I am unwilling to have them taken out, in fact they have not been cased twelve months, and I thought of boring a hole in an obscure corner with bit and brace, and inserting a saturated sponge, and then closing it again.
"Waterton says — 'The atmosphere of spirit of turpentine will allow neither acarus nor any insect to live in it.' Do you believe this?"
My answer to him, and to all such correspondents, was that I had repeatedly proved that all such little vermin did not care a bit for the fumes of benzoline, nor of any spirits whatever, as I had caused gallons of turpentine, etc.., to be poured into large cases containing specimens without producing the smallest effect, unless it absolutely touched them, but that I had partly succeeded by introducing cyanide of potassium (deadly poison) into small cases containing birds, through a hole bored for the purpose; but it was objectionable —
(I) on the score of its danger to health, should the poisonous vapour escape; and
(2) because it deliquesced rapidly in any but the driest atmosphere, by its affinity for damp, and, consequently, often caused mildew in cases of birds, etc.., into which it had been introduced. The fumes of sulphur during combustion are, on the contrary, really of service in destroying insect life, as evidenced in the fumigation of hospital wards, etc.., but I cannot tell how anyone may burn sulphur in specimen cases without half choking himself, and probably setting on fire the fittings and spoiling the work altogether. It is also objectionable because it readily discharges certain colours from fabrics, flowers, and birds' feathers. My advice is, therefore, to pull to pieces any case infested with insects, to burn all fittings not absolutely valuable, and to drench with turpentine all specimens, together with all the rockwork and fittings desired to be retained. [Footnote: I would indeed advise the destruction by burning of the birds themselves even, should they be common specimens, or easily replaced.]
Crude creosote, in little pots or saucers, is a great deterrent to the visits of insect plagues; it cannot, however, be exposed openly, as its scent is overpowering and decidedly unhealthy for use in private houses. In museums it does very well if cased up.
With regard to camphor in museums, although it is so constantly used, I consider it of no use as a deterrent. A small piece of tallow candle is equally efficacious, and of late I have had much more faith in insect powders, the best of which is, I believe, compounded of the petals of the Russian tansy (Pyrethrum roseum). This has certainly some principle contained in it not obvious to our senses. It is perfectly harmless to man, and to domestic animals, but on insects its action is entirely different. I cannot as yet discover whether insects eat it, or if its smell overcomes them, whether it repels, or attracts them to their doom. A series of experiments has left me just as much in the dark as ever. Certain it is that I have never found insects among skins over which it has been strewn.
There is, however, one slight objection to its use, which is that it stains light-coloured skins, if at all greasy, with its fine, brownish-yellow dust. This is, however, but a trifle, easily avoided, in face of its unquestionable value. I have used it now for many years, and have never had cause to alter my opinion as to its efficacy. The best only must be procured, from some well-known wholesale house, price about 3s. per lb. That sold made up in small quantities is generally adulterated and useless. No curator should ever be without it, and a small quantity should always be placed inside a newly-made skin. It can also be worked up in many of the preservative pastes, or macerated in spirit as a wash, for the inside of skins.
Baking or stowing maggot-infected specimens is recommended by some authors, but I strongly object to it in the case of old or valuable skins, firstly, because the heat can seldom be properly regulated, unless in an apparatus specially constructed; secondly, because heat sufficient to kill the larvae is also sufficient to crimp or twist some part of the plumage or render the skin, if an old specimen, too crisp or tender for ultimate handling; thirdly, because even a moderate degree of heat is sufficient to set free the fat contained in the skin, and thus spoil the feathers.
Perhaps the tyro may remark, "But in a preserved and stuffed skin there ought to be no fat to ooze out." Quite true, there ought not to be, but as skins are usually dressed with arsenical soap, the fat, instead of being dried up, is beautifully conserved, ready to run out at the slightest provocation, or be drawn out by the capillary attraction of the threads used in sewing up — another hard knock for arsenical pastes!