insects so dark and dense that even when cleared in xylol they obstruct the light and are visible only as silhouettes. Such specimens are often improved by bleaching. Naturally colorless and very thin-skinned specimens may become invisible when cleared. These should be dyed. The stain used to color these specimens will not “take” unless they also have been treated briefly with a bleaching solution, so the very dark and the very light require the same kind of special treatment before the dehydration begins. The bleach commonly used for this purpose in laboratories is a 10% aqueous solution of sodium hydroxide. Common household “Chlorox,” which is a 5% aqueous solution of sodium hypochlorite, does about as well. Put a small quantity of the bleaching solution in a glass dish, and place the dish on a white paper so that can see the specimen easily. Transfer the specimen to this solution from the first alcohol bath. Watch it closely, through the microscope if possible. Great care is necessary to avoid over bleaching. When the appendages become pale and easily movable, it is time to stop. Further treatment will dissolve the membranes of the joints, and the insect will fall apart. Rinse the specimen in clear water to remove the bleach, then return to dilute alcohol and continue the preparation as with un- bleached specimens. Bubbles of gas are sometimes formed inside of the body during bleaching. These will probably dissolve before the preparation is com- peted. If still present when the insect reaches the final bath, squeeze the abdomen gently to force the bubbles out through the needle hole. There are many stains which may be used to tint colorless specimens. Basic fuchsin is one of the more commonly used. It is a clear purple-red dye which you can buy, ready to use, from a scientific supply house. Apply it to specimens which have been bleached and run up to 95% alcohol. Put a little of the dye in a small container and allow the specimen to soak in it for a minute or two. Rinse in 95% alcohol, If the insect is not bright pink all over, dip it again. but do not permit it to become too dark. After dying and rinsing in alcohol, continue the preparation with carbol-xylene, xylene, and balsam, as has already been described. After seeing what this method of slide preparation can do, you might like to try more complicated and professional ones. For expert advice, consult an article called “Mounting Aphids and Other Small Insects on Microscope Slides” by E. O. Essig, which was published in the January, 1948, issue of the “Pan-Pacific Entomologist. If you do not have access to a museum or university library which subscribes to this journal, you can obtain a copy for seventy-five cents by writing to the California Academy of Sciences, San Francisco 18. California. DRY MOUNTING BY CHEMICAL DEHYDRATION There are many large soft-bodied arthropods which cannot readily be inflated. Some of these can be dry mounted by replacing their natural moisture with a liquid which so hardens the tissues that they shrink but little when that liquid is removed. To minimize distortion, the replacement is accomplished by degrees, delicate and succulent specimens pro- gressing more gradually than leathery ones. The simplest method is to remove the water with alcohol and the alcohol with xylene, exactly as though the animal were to be slide-mounted. Xylene evaporates rapidly, leaving the specimens dry, rigid, and usually unwrinkled, but somewhat smaller than in life. Al- though a pattern may persist, color will be almost wholly lost. Species which are translucent when living come out perfectly opaque. The reagents used to dehydrate large arthropods are those used in slide preparation: 70 and 95% alcohol, carbol-xylene, and xylol. Additional equipment includes: 1. Stender dishes or small covered jars, 2 or 3 inches deep and big enough around to accommodate the outstretched legs of your largest specimen. If you are preparing one specimen only, one dish will do. Change the liquids. If you are going to mount a series, provide one dish for each bath, and transfer the specimens. 2. Insect or dressmaker's pins, and if possible, some needle points or “minuten nadeln.” 3. A few pieces of cork or balsa wood about 1/8” thick and small enough to fit easily into the dishes. 4. Forceps, with which to handle the specimens and the small pins. 5. Oil colors, for restoring the pigmentation of the finished product. Reagents, dishes, and other equipment, if not obtainable locally, should be ordered from a reliable scientific supply house. As an example of the process, let us suppose that you wish to mount a large spider in a walking position. First, observe how it stands in life, the height of the body from the ground and the attitude of the legs. Then, kill the specimen by dropping it into boiling water for about half a minute. Spread out the body on a chip of balsa wood and pose it carefully, bracing and supporting it with pins as shown in Fig. 12. During the process of dehydration, the chip floats up-side- down on the surface of the liquid, a fact which must be taken into account when placing the pins. When the specimen is secure against drooping, even in an in- verted position, fill a dish with 70% alcohol. Float the chip, face down, upon the surface. Put on the lid, and leave it over night. On the following day, remove the float from the