Herbarium specimens will last for hundreds of years if properly cared for. The best conditions for storage include low temperature (from 50–65ºF), low humidity, low light, and infrequent handling. Roaches and certain beetles will destroy plant specimens. You can kill insects in dried plant specimens by freezing them for three or four days, and keep them pest-free in a tightly-sealed plastic bag. There are various ways to achieve these conditions. In a herbarium, plants are stored in folders within airtight cabinets. Any dried plant material is frozen before entering the herbarium, and the space is periodically treated with a pyrethrin spray (an organic insecticide made from chrysanthemums). In the BRIT herbarium, plants are organized alphabetically by the plant family to which they belong, then by the genus, then by geographic area and the species to which they belong. This organization facilitates the use of the herbarium by researchers and the public. You may view an excerpt about how we file specimens in the BRIT herbarium in the appendix.