Sound is made by rasping the proboscis against ridges in this groove stridulitrum (stridulatory organ). They also possess two types of stridulatory organs. This may have led to the lack of the stridulatory organ. Some butterflies have organs of hearing and some species make stridulatory and clicking sounds. The hind legs rub against tiny "peg" like structures, referred to as stridulatory pegs. These are referred to generically as the stridulatory organs. "C. brunneus" produce song by moving stridulatory pegs against their elytra. They differ mainly in details of the stridulatory organ and sensory bristles (trichobothria). "D. heteracantha" possesses a stridulatory apparatus. The shape of their stridulatory mechanism is why they can produce these frequency ranges. Eneopterinae show a great diversity in stridulatory apparatus, signals emitted, and associated behaviour. The cymbium may also be used as a stridulatory organ in spider courtship. No stridulatory signals have been observed; sex recognition is done by contact only. In 2005, Richard Gallon described the monotypic genus "Mascaraneus", which lacks the stridulatory spike setae. The forward-facing side of the coxa of the first leg has stridulatory hairs.