Preservation: Methods for killing and preserving specimens varies by species group as well as life stage. Most hard-bodied stages are killed in a killing jar or frozen before being mounted on a pin for display in a collection box. Over periods of years, dry brittle specimens are vulnerable to color fading if exposed to sunlight and attacks by book lice or dermestid (carpet) beetles if kept in a dark place and/or without chemical protection such as the fumigant – paradichlorobenzene (PDB), the repellant – napthaline (moth balls) or the pest strip – dichlorvos (DDVP). Soft-bodied insects and immature stages are usually killed and preserved in some type of fluid such as rubbing alcohol or a special preservative fluid, sometimes after first being boiled in water, and are stored in vials. Keeping vials filled with alcohol over a period of years is difficult due to evaporation or leaks requiring periodic inspection and re-filling. Specimens of tiny arthropods like mites and thrips are usually mounted on microscope slides for study.

For in-depth information, see:

Killing specimens
Keeping good records
Preservation considerations