Crickets Lose Ability to Sing: “Evolution in Action”

Ten years ago male crickets on the Hawaiian islands of Oahu and Kauai began to fall mysteriously silent, and now scientists have discovered why.

Some male field crickets have wings that no longer produce noise. Photograph by Nathan Bailey

The culprit is a parasitic fly, relatively new to the region, that’s attracted to the sound of the male field cricket’s song. After the fly’s arrival, crickets on both islands underwent a genetic mutation on their wings that prevents them from singing, according to study leader Nathan Bailey, an evolutionary biologist at the University of St. Andrews in Scotland. By keeping silent, the crickets avoid becoming dinner.

These silencing mutations occurred separately on Oahu and Kauai at almost exactly the same time, creating a rare case of rapid, convergent evolution, according to a study published recently in the journal Current Biology.

“It’s not often you get to watch these things happening in the field,” said Robin Tinghitella, an evolutionary biologist at the University of Denver who studies field crickets.

“We are finding evidence of evolution in action happening right in front of us,” said Tinghitella, who was not involved in the new study.

Silenced Song

When the ancient Polynesians began their diaspora through the South Pacific—including Hawaii—they brought the field cricket with them.

Males sing by rubbing a pointed scraper on the end of one wing against a file on the other, which is a modified wing vein that contains several teeth. (Also see “World’s Loudest Animals—’Power Saw’ Cricket, More.”)

The sound resonates through special structures in the wing and lures the females toward an attractive male. The males’ song also serves several other functions, including a show of aggression.

This singing scheme has worked effectively for thousands of years on islands across the Pacific Ocean, but at some point after the crickets arrived in Hawaii—scientists still aren’t sure exactly when—the parasitic fly Ormia ochracea arrived. (See Hawaii pictures.)

The flies’ larvae use the song to find a male cricket and then burrow inside. The larvae then consume the male from the inside out, using the nutritious cricket to aid their development. Within a week, the cricket is dead and the larvae are developed and ready to move on.

Not Over Till the Male Cricket Sings

Bailey and colleagues studied changes to the wing shape of crickets from both islands. Because the changes are slightly different in each population and the mutations occurred in different parts of the genome, Bailey is confident that the mutations happened separately on each island.

“Losing the ability to sing means a lot of behavioral dynamics will be changed,” he noted. For instance, these quiet males may have a tougher time finding females. (See “Cricket Has World’s Biggest Testicles (But Puny Output).”

Interestingly, though, the silent males have a strategy—mooching off males that can still sing.

“On Kauai, there are still roughly 5 percent [of] normal males, whereas about half of the males we found on Oahu are normal,” Bailey said.

The silent males depend on their more vocal counterparts to sing to attract females: When the females come to check out the singing males, the silent males pounce.

Just call them the strong, silent types.

Follow Carrie Arnold on Twitter and Google+.

Carrie is a freelance science writer living in Virginia. When she's not writing about cool critters, she's spending time outside, drinking coffee, or knitting. You can visit her website at http://www.carriearnold.com
  • Ima Ryma

    Mr. Cricket for ages sang
    A luring South Pacific tune,
    Aimed at lady cricket shebang
    Over Mr.Cricket to swoon.
    Then came a parasitic fly,
    Also quite lured by the song’s sound,
    Causing Mr. Cricket to die
    By burrowing in him around.
    So Mr. Cricket quickly changed
    His tune to silence so to solve
    Unwanted guests, and rearranged
    His come on – he had to evolve.

    Hush hush woo for Mr. Cricket.
    The singing – just had to kick it.

  • Mojtaba Najafi

    I wonder how is it possible for evolution to take such a quick pace. Wouldn’t it mean less rate of animal extinction?
    By the way, fascinating poem, Ima. To tell the story in such a beautiful rhyme is just wonderful.

  • Joshua Alvarez

    This isn’t evolution in action! This is actually an example of micro-evolution. Read more here –> http://on.fb.me/1tLixMt

  • Jake

    This kind of reminds me of what I’ve heard about rattlesnakes in Texas losing their ability to rattle: A bunch of rattlesnake roundups take place there in which snake hunters collect hundreds (thousands?) of snakes for festivals. Naturally, the snakes that usually get found tend to rattle the most. As a result, the ones that are left tend to be the quiet ones that give little or no rattle warning.

    This external selection pressure has favored these silent rattlesnakes, who get to reproduce and spread their genes. In the past, when the buffalo were roaming the Texas plains, I imagine the selection pressure was the reverse: That is, the snakes that didn’t rattle often got smashed underfoot by an oblivious grazing buffalo.

    It seems the parasite is creating a similar selection pressure on crickets.

  • nmgene

    We are over run with crickets here in Arizona and they dont sing. The crickets in Michigan do but not here.

  • Lemon Juice

    I have never heard of this. That’s a really new thing for me. But why the scentists in our country never give these funny knowledge to publics?

  • Ethne

    Natural selection I’d believe. More of the male silent crickets were left to breed and their “silent mode” carried to the next generation. Evolution? The term evokes the idea of the transformation into a new species, not a modified species. Not buying it!

  • Jason

    This isn’t evolution, it’s still a cricket, this is called natural selection whereby the loudest crickets are killed and the quiet ones survive.

  • manisha

    It is due to the process of Natural Selection i.e survival of the fittest(queit ones).

  • manisha

    It may be due to natural selection i.e survival of the fittest(silent ones),but not evolution because cricket remains cricket.

  • Rhonda Oliver

    Such odd comments. Natural selection is a driving force of evolution. It is part of the evolutionary process. To say it is natural selection and not evolution shows a lack of understanding as to what evolution is.

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