Tiny water insect makes record-breaking song with his penis

By Ed Yong | June 17, 2011 8:00 am

If you walk by a European river on a summer’s day, you might get to hear the animal kingdom’s champion vocalist. His song sounds like a train of chirps, and from a metre away, it’s as loud as whirring power tools. The din is all the more incredible because it is produced by an insect just two millimetres in length – the lesser water boatman, Micronecta scholtzi

Micronecta means “small swimmer” and it is aptly named. It’s among the smallest of the several hundred species of water boatmen that row across the bottom of ponds and streams with paddle-shaped legs. The males are the ones that sing, and they often do so in large choruses to attract the silent females. These songs are famously loud. Even though the insect lives underwater, you can hear its call from the riverbank, several metres away.

Now, Jérôme Sueur from the Natural History Museum in Paris has measured Micronecta’s song using underwater microphones. He found that it the small swimmer is a record-breaker. On average, it reaches 79 decibels, about the level of a ringing phone or a cocktail party. But at its peak, it reaches 105 decibels – more like a car horn, a power tool or a passing subway train.

There are animals that make far louder calls. The record goes to the sperm whale, which can create clicks of around 236 decibels underwater (equivalent to 170 decibels on land). Other animals, including elephants, hippos and dolphins can produce louder calls than Micronecta.

But pound for pound, there is no competition. All of these animals are very big, and it stands to reason that large objects can produce louder sounds – think about the difference between a concert amp and a set of headphones. The sperm whale, for example, grows up to 16 metres in length and weighs up to 14 tonnes. Micronecta, on the other hand, produces its phenomenal song with a body that’s no bigger than one of these letters. Sueur compared the ratio of call intensity to body size for 227 different animals, from whales to insects, and found that the water boatmen out-sang them all.

How does such a tiny insect make such a loud noise? It’s not clear. It seems to do so by rubbing its ribbed penis against ridges on its belly, playing its genitals like a miniature fiddler. But the “bow” here is just 50 micrometres long, and there are no obvious body parts to amplify the noise.

But maybe the amplifier isn’t a body part at all. Like other water boatmen, Micronecta traps a layer of air around its body using microscopic hairs. This layer helps it to breathe, but Sueur speculates that it could also act as an echo-chamber, reflecting the sound of the penis-fiddling again and again. The details, however, are a mystery. As Sueur writes, “To observe the micro-mechanics of such a small system remains a significant challenge.”

Sueur also has an idea about why the water boatman’s song is so loud. He compares the song to the complex melodies of birds or the long antlers of deer – it’s a sexual signal that indicates a strong, powerful mate. If females prefer loud males over quiet ones, the male’s song would become exaggerated over time.

There are some obvious ways of testing this. If Sueur is right, females should prefer louder males, which should be easy to test with speakers and some recordings. Sueur also thinks that M.scholtzi probably has no predators that hunt by sound – otherwise, such hunters would limit the evolution of an extreme song by snatching up the loudest males. We know nothing about what eats M.scholtzi and Sueur plans on finding out.

Reference: Sueur, Mackie and Windmill. 2011. So Small, So Loud: Extremely High Sound Pressure Level from a Pygmy Aquatic Insect (Corixidae, Micronectinae). PLoS ONE http://dx.doi.org/10.1371/journal.pone.0021089

More on animal calls:

Comments (15)

  1. marsha

    You can’t read this story with a straight face. Very interesting and quite funny.

  2. Can a recording contract be far behind?

  3. For these boys really size doesn’t matter

  4. i_am_leech

    Another proof for the saying about importance of sizes ,-)

  5. Dan

    Aaargh, how can you leave us high and dry without an mp3 of this sound?!

  6. Adela

    Dan there is an MP3 at the page that the official bug name links to, and pretty pictures.

  7. So long as it doesn’t tweet pictures of its package; the other bugs will ask it to step down.

  8. HL_guy

    Imagine if they had Twitter… the scandal.

  9. Charles Sullivan

    Where’s the greater water boatman? That’s what I want to know.

  10. Marc

    When I saw the headline, I thought it was another story about Anthony Weiner.

  11. Gunnar

    Some possible contenders for the title “loudest animal by size” are the snapping shrimp – a group of Crustaceans in the family Alpheidae. Using their asymmetrical claws, they can produce sounds as high as 218 dB. The sound is used both to stun prey and to communicate with other members of the same species.

    See for instance http://www.youtube.com/watch?v=ONQlTMUYCW4&feature=related.

    It is, however, not as nice as a good erotic penis song.

  12. They looked at snapping shrimp – not even close!

  13. Gunnar

    Victory for the penis! Hurray!

  14. Matt B.

    A singing sword?

    I think the method of comparison should avoid the presumption that size and loudness are in a linear relationship. Sizes and loudnesses of various animals should be plotted to find a curve that gives an expected output for each input. (Statisticians must have a word for this; is it “regression”?) Then the animal that has the highest ratio of loudness to expected loudness wins.

  15. Hello world, my name is penis.

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