Caterpillars and other immature stages of insects should be preserved in
80 per cent grain alcohol. Caterpillars, grubs, and maggots should first
be heated 5 to 10 minutes in water just at the boiling point. This
treatment sterilizes the specimens and prevents their discoloration by
bacteria in the digestive system.
Many soft-bodied adult insects, including bristletails, springtails,
stoneflies, and caddisflies, also should be preserved in fluid. If
pinned, they shrivel to such an extent that few identifying characters
can be seen. The preserving fluid in the vials in which insects have
been placed should be changed at the end of the first day or two.
Some hard-shelled insects may be preserved in fluid. Ants and beetles
may be thus treated temporarily and later pinned and dried.