Direction Leaflet Number Six HOW TO PRESERVE A COLLECTION OF SOFT-BODIED INSECTS AND SPIDERS By ALICE GRAY Department of Insects and Spiders The American Museum of Natural History Although most adult insects are preserved by air- drying only, the general collector will find, among his catch, many interesting creatures which cannot be so treated without intolerable distortion. Almost all spiders, ticks, and daddy-long-legs, for instance, are so thin-skinned and succulent that, if simply dried, they shrivel beyond easy recognition. So do the eggs, larvae, and pupae of most insects, and the adults of such diverse kinds as termites, silver-fish, aphids, and many others. Soft-bodied arthropods can be dehydrated artifi- cially, with comparatively little distortion, by methods outlined later in this paper. The processes are, hower, uncertain, laborious, and exacting. Since small but important characters are sometimes obliterated by desiccation, only those specimens which are required for exhibition, rather than for study, should ordinarily be mounted dry. LIQUID PRESERVATION Study specimens, the majority of those taken by any serious collector, are usually killed and permanently preserved in ethyl alcohol somewhat diluted with water, as described in Leaflet Number Three. If you are interested in soft-bodied insects and spiders of all sizes, you will find it convenient to have at hand, in labeled bottles, stock solutions containing ethyl alcohol in various proportions. Assuming the available alcohol to be “completely denatured,” and of the best quality, it will contain about 95% of ethyl alcohol and 5% of methyl alcohol and gasoline. The relative volumes of denatured alcohol and water in the most useful mixtures will then be these: Approximate concentration | Parts by volume | Parts by volume | Use of ethyl alcohol | denatured alcohol | water | 50% | 10 | 9 | For killing very delicate specimens. 60% | 12 | 7 | For “stepping-up” delicate specimens. Rarely needed. 70% | 14 | 5 | For preserving delicate specimens and killing tougher ones. 80% | 16 | 3 | For preserving specimens of average or large size. If you have, or can borrow, a measuring graduate of 100 cubic centimeters capacity, you can easily prepare alcohol of any given concentration from that of any known greater concentration in this manner. Fill the graduate with alcohol to the mark corresponding to the desired percentage of the mixture. Then add water until the total volume reaches the mark corresponding to the known percentage of the original alcohol. Thus, to make a 70% mixture from a 95% solution, fill the graduate with alcohol to the 70c.c. mark and add 25c.c. of water, making 95c.c. in all. The proportions listed in the table above were derived in this way, and although only approximate, are accurate enough for practical purposes. If the water in your district is conspicuously “hard,” you might use distilled water in mixing your reagents, though “soft” tap-water is usually all right. Alcohol of full strength, 95% can be used as a preservative for the larger species, but it will probably make them so rigid that they must be soaked in water before they can be manipulated for examination. If your collection must go for long periods unattended, so that it is in danger of drying out, add to the stock preservative solutions about two percent of