Cerambycidae: Acanthocinus aedulis male on Scots pine showing the stridulatory organ between the prothorax and anterior elytra (longitudinally oriented "pars stridens" in center-posterior end of dorsal prothorax). Both sexes can "squeak" or stridulate rather loudly. I have observed females stridulating when a male is guarding and she is laying eggs. Both sexes stridulate vigorously if you pick them up. The "plectrum" or scraper is located on the underside of the dorsal (upper side) part of the prothorax (the piece after the head). The "pars stridens" is the "comb" structure whose "teeth" are plucked or scraped. When one plucks a comb you get a sound, likewise, during stridulation. The "comb" or pars stridens (in latin) is made up of may fine rows of lines (or teeth) like on a phonograph record. In fact if the light strikes the pars stridens from the correct angle the whole area diffracts light into a spectrum of rainbow colors! You can see another pars stridens on top of the head of a female bark beetle from California, Ips paraconfusus where you can see the rainbow colors.

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Images © 1996 by John A. Byers, Chemical Ecology.