The sounds you heard were made by adult spruce beetles (Dendroctonus rufipennis) while in a glass jar. Like several other bark beetles, spruce beetles make these sounds ("stridulate") by rubbing the edge of their hard forewings over a toothed ridge on their abdomen. Bark beetles make different sounds during courtship, to drive away competitors, and during times of stress.
These sounds were recorded by Connie Mehmel and Gordon Hempton on June 4, 2002.
This webpage was last updated on July 29, 2005; reformatted May 2008.