Fireflies: The Invertebrate Opera

By Carl Zimmer | June 29, 2009 11:59 pm

Fireflies are the topic of my story on the cover of the New York Times science section tomorrow. It’s the result of a visit I paid last Friday evening to a meadow in Massachusetts, where I listened to Sara Lewis of Tufts University explain the sultry, complex tale of sex, deception, and death that was playing out in front of me.

I first got to know Lewis’s work last summer, when I decided I wanted to include fireflies in my next book, The Tangled Bank: An Introduction to Evolution. Lewis co-authored a fascinating review of firefly biology last year (free pdf from Lewis’s web site). I particularly liked this chart, which shows how different species have evolved different flash signals.

firefly-code.jpg The male, flying around, releases a certain pattern of flashes–a single one second pulse followed by a five secondin the case of Photinus pyralis, for one example. And if a female P. pyralis, sitting on a blade of grass, likes what she sees, she responds three seconds later. Not one. Not six. Three. If she responds at the right interval, he knows he’s found a female of his own species and zeroes in, sending more flashes. She may also be signalling other males at the same time; which male she chooses may come down to subtle features of the flash pattern–for example, a rapid series of pulses as opposed to a slow one.

You can, as I discovered, speak their language with a penlight. You can even play the male or the female, depending on your mood.

There’s lots of strange business going on out among the fireflies. I didn’t have room in the article to describe some of Lewis’s new areas of research. Because female fireflies mate with several males, they can end up with sperm from several males inside them at once. Studies on other animals have suggested that females can choose which male’s sperm they’ll use to fertilize their eggs. Males can also inject chemicals with their sperm that increase their odds of fertilization. It’s clear that in many species, female preferences and male competition can continue after mating ends.

No one knows how this struggle plays out in fireflies. Adam South, one of Dr. Lewis’s graduate students, is investigating this side of the evolutionary equation. He is mating female fireflies with two males apiece and then collecting the eggs they lay. Using DNA tests, he’s determining the paternity of the eggs. Perhaps the males with more attractive flashes have more offspring.

What scientists like Lewis know about fireflies is remarkable, but it’s dwarfed by what they don’t know. Are fireflies on the decline, for example? Unfortunately, there’s no good long-term data. But that’s now an opportunity for some citizen-science you can get involved in. Lewis and some former students have helped organize Firefly Watch, based at the Boston Museum of Science. You can make your backyard part of biology’s new frontier.

Comments (19)

  1. Christina Viering

    Fireflies are fascinating, thanks for the info!

  2. D.M. Hayes

    Great peice Carl. Why is it that the NYTimes can’t italicize scientific names? It drives me nuts!

  3. John Kwok

    Carl,

    This is a bit off topic, but I just looked at the Amazon.com webpage for your forthcoming book and it doesn’t have a publication date. For your sake I hope it’s not due out this fall since it will be competing against Dawkins’s new book.

    Best,

    John

    CZ: John, if you scroll down on the Amazon page, the Tangled Bank is due out October 1. We’ve just handed over the files to the printer, so I think we’re actually going to hit that date. As for Dawkins’s book, which is out on September 22, I think Amazon should offer one of their two-book-package-deals!

  4. John Kwok

    Carl –

    I agree with you completely, but I don’t think Simon and Schuster – Dawkins’s publisher – would be thrilled, especially when they gave him a substantial advance for this. Am sorry that your book is coming out almost two weeks after Dawkins’s.

    Thanks,

    John

  5. Brian

    Some years ago I was in Costa Rica and I was fooling around near dusk with a camera. There were fireflies in the area and I was trying to get a flash picture of one (it being too dark to get a shot otherwise). The fireflies were of course advertising their presence, so at least they were easy to find.

    After a few problematic shots (it’s nearly impossible to frame a shot in twilight), I had a crazy idea. My flash charge indicator was a 2-stage affair, and when charging it was the same colour that the fireflies were flashing. So I turned the camera around and showed a firefly my LED.

    Well! The poor firefly was beside himself (herself?)! I could hardly see a thing, but my hand was on the flash and the firefly was all over that flash unit. It was like being attacked by a butterfly. No danger for me, and I’m a tiny bit worried for the firefly.

    I had always assumed the the LED colour was the sole attractant. However your article indicates that I must have hit upon a compatible blink interval too. That was a complete fluke because there’s no way for the camera operator to control that.

  6. Martin

    When I mentioned this article to my wife, she instantly came back with (apologies to The Doors):

    C’mon baby, light my ass
    C’mon baby, light my ass
    Let’s roll around in the grass
    C’mon baby, light my ass

    I’ll never look at fireflies the same way again.
    Thanks for the article, well-written as always.

  7. Your timing on this article couldn’t be any better and I greatly appreciate it. My company, StoneGears has just released an iPhone App specifically to attract and communicate with fireflies. This info is going to help shape our next version. Please feel free to get in touch!

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The Loom

A blog about life, past and future. Written by DISCOVER contributing editor and columnist Carl Zimmer.

About Carl Zimmer

Carl Zimmer writes about science regularly for The New York Times and magazines such as DISCOVER, which also hosts his blog, The LoomHe is the author of 12 books, the most recent of which is Science Ink: Tattoos of the Science Obsessed.

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