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Insects and other
arthropods stridulate by rubbing together two parts of the body. These are referred to generically as the
stridulatory organs. The mechanism is best known in
crickets,
mole crickets, and
grasshoppers, but other insects which stridulate include
Curculionidae (weevils and bark beetles),
Cerambycidae (longhorned beetles),
Mutillidae ("velvet ants"),
Reduviidae (assassin bugs),
Buprestidae (metallic wood-boring beetles),
Hydrophilidae (water scavenger beetles),
Cicindelinae (tiger beetles),
Scarabaeidae (scarab beetles),
Passalidae (Bessbugs),
Largidae (bordered plant bugs),
Miridae (leaf bugs),
Corixidae (water boatmen, notably
Micronecta scholtzi), various
ants (including the
Black imported fire ant,
Solenopsis richteri), some
stick insects such as
Pterinoxylus spinulosus, and some species of
Agromyzidae (leaf-mining flies). While
cicadas are well-known for sound production via abdominal
tymbal organs, it has been demonstrated that some species can produce sounds via stridulation, as well. Stridulation is also known in a few
tarantulas (Arachnida), certain centipedes, such as
Scutigera coleoptrata, and some
pill millipedes (Diplopoda, Oniscomorpha). It is also widespread among decapod crustaceans, e.g., rock lobsters. 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). One of the
wolf spiders,
Schizocosa stridulans, produces low-frequency sounds by flexing its abdomen (tremulation, rather than stridulation) or high-frequency stridulation by using the cymbia on the ends of its
pedipalps. In most species of spiders, stridulation commonly occurs by males during sexual encounters. In the species
Holocnemus pluchei, females also possess stridulatory organs, and both sexes engage in stridulation. In the species
Steatoda nobilis, the males produce stridulation sounds during mating. The anatomical parts used to produce sound are quite varied: the most common system is that seen in grasshoppers and many other insects, where a hind leg scraper is rubbed against the adjacent forewing (in
beetles and
true bugs the forewings are hardened); in crickets and
katydids a file on one wing is rubbed by a scraper on the other wing; in longhorned beetles, the back edge of the
pronotum scrapes against a file on the
mesonotum; in various other beetles, the sound is produced by moving the head—up/down or side-to-side—while in others the abdominal
tergites are rubbed against the
elytra; in assassin bugs, the tip of the mouthparts scrapes along a ridged groove in the
prosternum; in velvet ants the back edge of one abdominal tergite scrapes a file on the dorsal surface of the following tergite. 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 and tarantulas). This kind of communication was first described by Slovenian biologist
Ivan Regen (1868–1947). ==Vertebrate stridulation==