Most hard-bodied insect specimens and some other hard-bodied invertebrates such as certain
Arachnida, are preserved as pinned specimens. Either while still fresh, or after rehydrating them if necessary because they had dried out, specimens are transfixed by special stainless steel
entomological pins. As the insect dries the internal tissues solidify and, possibly aided to some extent by the integument, they grip the pin and secure the specimen in place on the pin. Very small, delicate specimens may instead be secured by fine steel points driven into slips of card, or glued to card points or similar attachments that in turn are pinned in the same way as entire mounted insects. The pins offer a means of handling the specimens without damage, and they also bear labels for descriptive and reference data. Once dried, the specimens may be kept in conveniently sized open trays. The bottoms of the trays are lined with a material suited to receiving and holding entomological pins securely and conveniently. Cork and foam plastics are convenient examples. However, open trays are very vulnerable to attack by
museum beetle and similar pests, so such open trays are stored in turn inside glass-topped, insect-proof drawers, commonly protected by suitable
pesticides or
repellents or barriers. Alternatively, some museums store the pinned specimens directly in larger trays or drawers that are glass-topped and stored in cabinets. In contrast to such dried specimens, soft-bodied specimens most commonly are kept in "wet collections", meaning that they are stored in alcohol (most commonly 70%
ethanol) or similar preservative or
fixative liquids, according to the intended function. Small specimens, whether hard or soft bodied, and whether entire,
dissected, or
sectioned, may be stored as
microscope slide preparations. ==Wet specimens==