[Alcohol and Corrosive Sublimate.]—The same author recommends another preparation consisting of alcohol with a variable quantity of corrosive sublimate added, the strength of the solution varying from 100 parts of alcohol to 1 part of corrosive sublimate for the strongest, to one-tenth of 1 part of sublimate in 100 parts of alcohol for the weakest. The insects are allowed to remain in this mixture not longer than two hours before drying. The last-described preparation is said to preserve the specimens from mold. Both of these solutions are very poisonous and should be used with care.
[Two Liquids to preserve Form and Color.]—Professor Packard also quotes the formula of A. E. Verrill for preserving insects in their natural color and form. Two formulas are given; the first consists of 2½ pounds of common salt and 4 ounces of niter dissolved in a gallon of water and filtered. The specimens should be prepared for permanent preservation in this solution by being previously immersed in a solution consisting of a quart of the first solution and 2 ounces of arsenite of potash in a gallon of water. Professor Packard gives also the formula of M. H. Trois for preserving caterpillars, for which it is claimed that the colors of the caterpillars are preserved perfectly, even when exposed to strong light. The formula for this solution is as follows:
| Common salt | grams | 2.35 |
| Alum | do. | 55 |
| Corrosive sublimate | centigrams | 18 |
| Boiling water | liters | 5 |
Allow the liquid to cool and add 50 grains of carbolic acid, and filter after standing five or six days.
[Glycerin.]—Glycerin, either pure or mixed with water or alcohol, is frequently used to preserve the larvæ of delicate insects. It preserves the color and form better than alcohol, but particularly in the case of larvæ, it causes a softening of the tissues which renders them unfit for study.
[The Wickersheim Preserving Fluid.]—This valuable preserving fluid has been known for some time, but is not very commonly used, on account of frequent disappointment due to the difficulty attending its preparation. It is claimed for it that animal or vegetable bodies impregnated with it will retain their form, color, and flexibility in the most perfect manner. The objects to be preserved are put in the fluid for from six to twelve days, according to their size, and then taken out and dried in the air. The ligaments remain soft and movable, and the animals or plants remain fit for anatomical dissection and study for long periods, even years. It is said to be especially valuable for the preservation of larvæ and soft-bodied insects. In order to perfectly preserve the colors, it is necessary to leave the specimens in the fluid, or, if they are taken out, they should be sealed up in air-tight vials or vessels. The formula for the fluid is as follows:
Dissolve 100 grams alum, 25 grams common salt, 12 grams saltpeter, 60 grams potash, 10 grams arsenious acid in 3,000 grams boiling water. Filter the solution, and when cold add 10 liters of the liquid to 4 liters of glycerin and 1 liter of methyl alcohol.
Footnote:
[7] Annual Report of the Smithsonian Institution for 1886, Part II, Report of the National Museum, pp. 182–186. Washington, 1890.