Stridulation

[strij-uh-leyt]

Stridulation is the act of producing sound by rubbing together certain body parts. This behavior is mostly associated with insects, but other animals are known to do this as well, such as a number of species of snakes and spiders. A dedicated stridulation apparatus has also been discovered in males of one (as of April, 2007) bird species, the Club-winged Manakin. Common onomatopoeic words for the sounds produced by stridulation include chirp and chirrup.

Insect stridulation

Insects and other arthropods stridulate by rubbing together two parts of the body. These are referred to generically as the stridulatory organs, though in many groups the entire structure is called a stridulitrum. The mechanism is best known in crickets and grasshoppers, but other insects which stridulate include Scolytinae (bark beetles), Cerambycidae (longhorned beetles), Mutillidae ("velvet ants"), Reduviidae ("assassin bugs"), Glaresidae ("enigmatic scarabs"), the Black imported fire ant (Solenopsis richteri), larval Lucanidae (stag beetles), Passalidae (Bessbugs), Geotrupidae (earth-boring dung beetles) and some species of Agromyzidae (leaf-mining flies). Stridulation is also known in some species of millipede (class Diplopoda).

The mechanism is typically that of one structure with a well-defined lip or ridge (the "scraper") being moved across a finely-ridged surface (the "file"), and vibrating as it does so, like the dragging of a phonograph needle across a vinyl record.

Stridulation in several of these examples is for attracting a mate, or as a form of territorial behaviour, but can also be a warning signal (acoustic aposematism, as in velvet ants). This kind of communication was first described by Slovenian biologist Ivan Regen (1868-1947).

Snake stridulation

A number of species of venomous snakes are known to stridulate as part of a threat display. They arrange their body into a series of parallel C-shaped (counterlooped) coils that they rub together to produce a sizzling sound, rather like water on a hot plate. The most well known examples are members of the genus Echis (saw-scales vipers), although those of the genus Cerastes (North African desert vipers) and at least one bush viper species, Atheris desaixi, are known to do this as well.

Spider stridulation

Most spiders are silent, but some tarantula species are known to stridulate. When disturbed, Theraphosa blondi, the Goliath tarantula, can produce a rather loud hissing noise by rubbing together the bristles on its legs. This is said to be audible to a distance of up to 15 feet (4.5 m).