Sex and Rock & Roll - The World's Loudest Penis?

If it's too loud nearby a river in Paris, you can blame M. scholtzi singing a raucous love song, exclusively by males wooing females.

From National Geographic Daily News:

{Note: A loud rock concert is at about 115 decibels...}

Engineers and evolutionary biologists in Scotland and France recorded the boatman--which is roughly the size of a grain of rice--"singing" in a tank. The aquatic insect's songs peaked at 105 decibels, roughly equivalent to the volume of a pounding jackhammer within arm's reach.

The chirps are loud enough that humans can hear the sounds while standing at the edge of a boatman's pond. Fortunately for nature lovers, though, nearly all the sound is lost when the noises cross from water to air.

Remarkably, the boatman creates his songs by rubbing his penis against his belly, in a process similar to how crickets chirp. Sound-producing genitalia are relatively rare within the animal kingdom, but animals have evolved hundreds of other ways to boost their hoots, howls, and snaps.

--Rachel Kaufman

From PLoS One:

Specimens of M. scholtzi were collected in a river in Paris (France, 48°49.42â²N-02°25.93â²E) and in a pond in Morsang-sur-Orge (France, 48°40.03â²N-02°20.59â²E) from August to September 2009 and 2010.

The mechanism behind the intense sound production of M. scholtzi is not clearly identified. The sound is produced by rubbing a pars stridens on the right paramere (genitalia appendage) against a ridge on the left lobe of the eighth abdominal segment [15]. This sound emission system does not measure more than 50 µm in length, and there are no obvious body or external resonating systems that could amplify the sound, as observed in insects, amphibians, mammals and birds [30]-[35]. The high sound output (~124 dB) observed in Panulirus spiny lobsters has been explained by the use of stick-slip friction instead of a classical stridulation [36], [37]. This mechanism might occur in M. scholtzi, but to observe the micro-mechanics of such a small system remains a significant challenge.