stridulating moth wang

SEM photo of Pyralid moth genitals showing ridges and scraper (From Conner 1999)

I’m on the radio, talking about one of my favorite sciency words:  Stridulation.

strij əˌlāt  VERB.

The act of rubbing two body parts together to produce a sound.  Sounds are usually made when a scraper is rubbed across a finely ridged surface.  Most common in grasshoppers and crickets, but beetles, true bugs, and spiders also produce sound this way.

Example use in a sentence: “I ran across the street in corduroy pants and made a loud stridulating noise.”

It can be hard to make a hookup if you’re a small insect, so many insects use stridulation to produce sounds that travel long distances. Insects sing to tell a mate where they are, and sometimes also to tell competitors where their territory is.

A few insects use their genitals to produce “acoustic emissions”.  And of course that’s what I talked about in the interview.  My part of the interview starts at 35:18.

Play the interview!

A bit more background on the insects I talked about:

Water boatmen (Corixidae) are little insects found swimming near the bottom of ponds and streams. They stridulate underwater; most species use antennal pegs they rub on their heads.  One tiny water boatman species, Micronecta scholtzi, is special. It holds the record for loudest stridulation… with a penis.  In fact, this minute insect—it’s entire body is only 2mm long––is the loudest animal on the planet in terms of noise produced with or without schlong stroking.

Male pygmy water boatmen rub their rod on a series of ridges on their belly, rather like a bow and a fiddle. The penis of the lesser water boatman is 50 micrometers long (0.005 mm).  That’s comparable to the width of a human hair sliced in half.  How loud a noise can they produce with their tiny penile whammy bar?  Between 90 and 105 decibels. That’s a sound level similar to a motorcycle. (The ultimate proof that size doesn’t matter when it comes to a penis.)


This isn’t the only phallic party trick in Class Insecta, though.  Waterbugs are impressively noisy, but some moths can jam sonar with their genitals. At least three different families of moths produce ultrasound with the same file and scraper system found in other insect singers, but in a rather unusual place.  They use their ultrasound both for sexy signals to attract a mate and as protection from predators.  How does one use naughty bits as protection from predators?

Bats use echolocation to bounce ultrasound off a potential snack, pinpointing its location.  By interfering with the sound returning to a bat’s ears, ultrasonic sonar-jamming moth ‘nads confuse the bat. Check out this video of ultrasound production.

The descriptions of the moth genitals that do this are cringe inducing: rasping scales … against needle like spines”, for example.  Generally, rasping spines and needles are not something associated with gonads unless you’re reading 50 Shades of Grey.

To produce the ultrasound, male moths rub modified “claspers”, structures normally used to grab females during mating. Female moths rub their “genital plates” together.  About the closest analogy I could make with a human would be rubbing your labia together to produce ultrasound.  (It’s not an accurate analogy, but I’m really hoping at least a few of you try it.)

The last of the genital stridulators I know of is a crane fly.  I’m afraid I have to report that the descriptions of this fly made me snorfle like a 12-year-old:

“the male began to vibrate his genitalia in bursts, and continued to do so nearly continually for more than 10min… the male’s genitalia function to produce stridulation during copulation….the function of this behavior and of these structures is to stimulate the female.”

From this research, one can only conclude that crane flies ARE apparently ribbed for her pleasure!  Also, that tantric crane fly sex lasts 10 minutes.

I’ve been focusing on the ribald aspects of genital stridulation, but all of these are as interesting for their evolutionary history as their titillating details. Thousands of insects stridulate, all in slightly different ways. A few of them have modified existing body parts to produce their symphony of science with some unusual instruments.  As Charles Darwin said, “from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.”  

Hopefully I’ve ruined “Air On A G-String” for you forever.
Gwynne D.T. & Edwards E.D. (1986). Ultrasound production by genital stridulation in Syntonarcha iriastis (Lepidoptera: Pyralidae): long-distance signalling by male moths?, Zoological Journal of the Linnean Society, 88 (4) 363-376. DOI:

Eberhard W. (2009). Genitalic stridulation during copulation in a species of crane fly,Tipula (Bellardina) sp. (Diptera: Tipulidae), Revista de Biología Tropical, 57 (1) DOI:

Conner ‘Un chant d’appel amoureux’: acoustic communication in moths, The Journal of experimental biology, PMID:

Sueur J., Mackie D., Windmill J.F.C. & Soares D. (2011). So Small, So Loud: Extremely High Sound Pressure Level from a Pygmy Aquatic Insect (Corixidae, Micronectinae), PLoS ONE, 6 (6) e21089. DOI:

Posted by Gwen Pearson

Writer. Nerd. Insect Evangelist. Have you heard the good news? BUGS!


  1. LOL. Wish I’d taken biology now.

  2. This is very interesting. Did not know that water boatmen were the loudest. I thought that distinction belonged to cicadas.

  3. Mark–it’s loudest as determined by sound pressure generated/body size. So, the loudest animal is actually a sperm whale (>200 dB); but when you look at ratio of body size/sound produced, the water boatman is clearly in it’s own class of noisy! Ed Yong’s paper that I linked and the original paper have more on that.

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