The first description of the stridulation of this beetle was written by the early entomologist René Antoine Ferchault de Réaumur in 1737:
when one holds it, it lets a little cry be heard, produced by the friction of its last abdominal segments against the elytra, the more one presses the elytra against the body, the louder it criesMore recent studies have confirmed this description, and also shown that stridulation is common in the Lily Beetle subfamily (Criocerinae). The stridulatory apparatus consists on a file on the last tergite - the dorsal end of the abdomen - made of microscopic parallel ribs, which are scraped by files of sharp denticles in the underside margins of the elytra. The sound is produced while the abdomen contracts, and these contractions can be amazingly rapid, up to 200 times per minute and is loud enough to be heard if the beetles are less than 30 cm from your ear. The high variability of the chirps and the situations in which they are produced suggest that this behaviour is a defence mechanism: the beetle will chirp if captured and the sound can startle the potential predator to release the beetle before swallowing it. In other beetle species chirping is used in intraspecific communication, with the lily beetle, is is yet another way of avoiding being eaten.
Michael Schmitt & Dieter Traue. 1990. Morphological and Bioacoustic Aspects oî Stridulation in Criocerinae (Coleóptera, Chrysomelidae). Zool. Anz, 1990, 225: 225-240.