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Speaker's Footnotes

Relevant references and citations — with detailed annotations — provided to TED by Sara Lewis.

  • 00:56

    Be assured that no real fireflies were harmed during the filming of this talk! The simulated fireflies in the jar and the field backdrop were created by Firefly Magic, whose landscape lighting products are designed to simulate the magic of real fireflies.

  • 01:47

    This four-hour time-lapse photograph taken by Spencer Black shows Phausis reticulata, the blue ghost firefly in the southern Appalachian Mountains. These glowing males fly in slow, meandering paths over the forest floor in search of their earthbound, flightless females.

  • 01:55

    This long-exposure photo was taken by amateur photographer Tsuneaki Hiramatsu near Okayama, Japan. These Genji fireflies (Luciola cruciata) fly over rivers because they live underwater during their juvenile larval stage.

  • 02:07

    This photograph was taken in Kuala Selangor, Malaysia by photographer Weng Keong Liew. In these fireflies (Pteroptyx malaccae), which are called kelip-kelip in Malay, males congregate in particular mangrove trees every night, where they flash synchronously for hours to attract flying females.

  • 02:30

    In this photograph of Japanese Hime fireflies (Hotaria parvula) taken near Niimi City, Tsuneaki Hiramatsu used time-lapse photography to take several continuous exposures, which he then combined into a single image.

  • 02:37

    Pictured in flight is a male big dipper firefly, Photinus pyralis — he’s about an inch, top to bottom (photographs by Terry Priest).

  • 02:37

    Nowhere on Earth do fireflies have deeper cultural significance than in Japan: The admiration for their ethereal beauty is clearly captured in this 1896 lithograph “Love of Fireflies” (蛍狩り) by Yosai Nobukazu. Information on this very rare lithograph from the private collection of Professor Ross Walker can be found at his online Ohmi Gallery.

  • 02:49

    Probably all of us know some cats who are mesmerized by fireflies — this white kitty was photographed by Terry Priest. Here’s a great site to find out more about evolution.

  • 03:21

    Down here in the grass, I’m checking out some female fireflies. (Photograph by conservation biologist Dan Perlman). Find out more about our ongoing firefly research at Tufts University.

  • 03:48

    Illustrating the spectacular diversity of beetles, this photographic mosaic is by artist and photographer Christopher Marley.

  • 04:10

    As fireflies blossomed over evolutionary time, they evolved remarkably diverse signals that enable them to find and hook up with potential mates. Among the 2,000 firefly species that exist today, some use invisible wind-borne perfumes, others use slow glows and still others use quick, bright flashes of light. The Boston Museum of Science’s Firefly Watch is a wonderful place to learn more about fireflies.

  • 04:49

    There are three major groups of flashing fireflies in North America: Photinus, Photuris and Pyractomena, also known as lightning bug fireflies. (Photograph of a big dipper Photinus pyralis male by Terry Priest.)

  • 04:59

    Bioluminescent creatures abound in the sea, but fireflies are among only a few land animals that can produce light.

  • 05:13

    Different creatures use different versions of luciferase, the enzyme that orchestrates the light-producing reaction. This schematic drawing is by David S. Goodsell from the Protein Data Bank, where luciferase was a featured "Molecule of the Month."

  • 05:55

    During their lives, fireflies undergo quite an amazing transformation known as complete metamorphosis. Originating among insects about 290 million years ago, this lifestyle has proven wildly successful over evolutionary time. Fireflies spend their childhood in a radically different juvenile stage called a larva (the plural is larvae, pronounced: "LAR-vee"). Depending on the climate, this juvenile stage lasts somewhere between several months and two years. These larval fireflies are fierce predators, using their sickle-shaped hollow jaws to inject immobilizing toxins and digestive enzymes into their prey. The photograph by Heinz Albers shows a glow-worm larva (Lampyris noctiluca) attacking a snail.

  • 06:17

    This unidentified lampyrid larva was photographed in Khao Yai National Park in Thailand by Nicky Bay. Firefly larvae often glow while they’re crawling around, and they also glow whenever they’re disturbed.

  • 06:25

    While firefly larvae use their lights as a warning signal, many other animals use bright coloration (often yellow, orange or red) to warn potential predators that they’re poisonous or distasteful. Monarch butterflies are one familiar example of this warning coloration, formally known as aposematism.

  • 06:37

    This is such a great example of evolution’s creative improvisation: The larval lights that originated to perform one function (anti-predator warning signal) eventually got retooled into something entirely new — an adult courtship signal. When this happens, evolutionary biologists call it an exaptation, so fireflies’ bioluminescent courtship signals are an exaptation that originated as a larval defense.

  • 06:50

    This proud male is a big dipper firefly (Photinus pyralis), photographed by entomologist and insect photographer Alex Wild. His light-producing lantern occupies two entire segments of his abdomen, which is typical for Photinus males. Big dipper fireflies could easily be the poster child for all US fireflies, as they’re found across the eastern US from Iowa to Texas, and from Kansas to New Jersey. They’re often abundant and fly close to the ground just at dusk, so even young children can easily capture them.

  • 07:22

    This long-exposure image by Alex Wild shows an Illinois field filled with males of the big dipper firefly (Photinus pyralis).

    This photograph beautifully illustrates how these fireflies got their common name: While they're flashing, males dip down and then rise up sharply, skywriting the letter J with light. More than 30 different species of Photinus fireflies live in North America, and the males of each species use distinctive flash patterns. This is how the females recognize the males belonging to their own species.

  • 07:59

    In Photinus fireflies, females have much smaller lanterns. In this big dipper female, it’s just the yellow spot visible in the middle of her second-to-last segment. While female Photinus fireflies typically can fly, they generally leave the job of mate-searching to males. (Photograph by Alex Wild.)

  • 08:24

    Photinus fireflies find their mates using a call-and-response dialogue spoken solely through flashes. (Photograph by Alex Wild).

  • 08:36

    The technical name for these firefly opinion polls is photic playback experiments, and we’ve done lots of these to figure out what females are looking for. For many different species of Photinus fireflies, we and others have found that females very consistently prefer more conspicuous male flashes. But exactly what females like best turns out to depend on the species. Some females — like Photinus pyralis — prefer longer duration male flashes, while in other species, females prefer male flashes with faster pulse rates. The student who’s testing female preferences here is co-author Taki Michaelidis, decked out in his full anti-mosquito gear.

    These and other experiments on firefly flash signals, mate choice and predation are summarized here.

  • 08:57

    Mating fireflies: Although the traditional idea of sexual selection stopped short with successful mating, it turns out that the tendrils of this key evolutionary process extend far beyond mere copulation. In most animals, each female will mate with several different partners, and these mating males don’t all share equally in siring the female’s offspring. In the face of such female promiscuity, males have devised many ways to ensure their paternity success. (Photograph of mating Photinus fireflies by me).

  • 09:10

    In many — though not all — fireflies, males give females a nuptial gift called a spermatophore (a sperm-containing package that’s manufactured by the male’s reproductive glands). See a photo.

  • 09:20

    It turns out that trading gifts for reproductive success is a pretty popular custom across the animal kingdom. These nuptial gifts come in multitudinous forms, including dead insects, spitballs, blood, love darts and more.

  • 09:32

    This lovely dissection and photo by Dr. Adam South lets us peer directly inside the mating couple to see the spermatophore as it’s being transferred to the female. (We’ve stained it red by feeding males sugar water spiked with a dye called rhodamine B for two days before mating.) You can also see the male’s many reproductive glands responsible for manufacturing the gift (lower portion), as well as the specialized female structures that receive sperm and digest the spermatophore (upper portion).

  • 09:53

    Once the firefly’s gift reaches the female, it takes on a lovely spiral shape, like the corkscrew-shaped pasta called rotini. Here we get to see the unusual (and rather embarrassing) situation where a male has prematurely released his spermatophore. (Photograph by Wilson Acuna.) Yet it also captures how expensive this bling is for a male: This gift is huge compared to the male’s body size!

    Gift-giving is an important part of firefly economics, because most fireflies eat little or nothing once they’ve become adults. Our radiolabeling studies revealed that a female uses protein from the male’s gift to help provision her eggs. And in another study, we found that the more often a female mates, the more eggs she can lay. So maybe it’s not surprising that females should try to use a male’s flash signals to predict what material resources he can offer. Sometimes this seems to work, but sometimes it doesn’t.

    Although I didn’t mention it in my talk due to time constraints, we’ve found that gift-giving also helps the males: Those with bigger spermatophores enjoy higher paternity success.

  • 10:15

    But the scariest predators by far just so happen to be other fireflies: the predacious Photuris fireflies. (Head-on view photograph by Dwight Kuhn). These big, active and fast-moving fireflies specialize in eating their smaller cousins, certain Photinus fireflies. Studies conducted by Jim Lloyd and others have documented the many devious ways they capture their prey.

  • 10:28

    Most fireflies taste quite nasty (trust me) because they contain defensive steroids called lucibufagins. Fireflies do have a few predators, for instance spiders, daddy long-legs and assassin bugs.

  • 10:42

    Around 1997, the late Tom Eisner, Jerry Meinwald and their colleagues at Cornell discovered that Photuris predators can’t make lucibufagins on their own: Instead, they need to obtain these defensive compounds from their prey. By sequestering the prey’s lucibufagins, these females gain protection for themselves and also defend their eggs against predators.

  • 10:53

    Providing a textbook example of aggressive mimicry, these "femmes fatales" lure in males of other species by mimicking the flash responses normally given by the prey's own females. These predators are smart, too. Females have signal repertoires: One female managed to lure in males belonging to four different prey species, using a distinctive mimicked response for each one. (Photograph of eavesdropping "femme fatale" by Don Salvatore, flying prey male by Terry Priest).

  • 11:42

    Predatory Photuris fireflies are actually pretty good at this — a female will seldom need to answer more than 10 males before she’s successful in snagging one. (Both photographs of Photuris eating Photuris prey are by Jim Lloyd.) The gory remains show what’s left of one Photinus carolinus male that was chewed up and spit out by a Photuris female. (Photograph by Lynn Faust.)

  • 12:28

    In 2010, participants from 13 countries wrote the Selangor Declaration on the Conservation of Fireflies, which recognizes that firefly populations are declining, and emphasizes the need for habitat protection to prevent their loss.

  • 12:40

    Our sheer ingenuity has enabled humans to conquer darkness, yet stray light can disrupt the natural cycles of all sorts of nocturnal creatures, including birds, turtles, frogs and insects. In the Swiss village of Biberstein, artist and firefly enthusiast Stefan Ineichen looked at how streetlamps affect the mating rituals of Lampyris noctiluca, the common European glow-worm. Glow-worm females are flightless, and they pay no attention to streetlamps in choosing a spot for their nightly display. But their males only search in darker places, avoiding the bright circles cast by streetlamps. So many lonely female glow-worms who display their wares near streetlamps will probably die before they get a chance to mate. (Photograph by NASA.)

  • 12:54

    This female glow-worm (Lampyris noctiluca) photo is by Jason Steel.

  • 13:33

    This one-hour time-lapse photo contrasting the precise pattern of star trails and the haphazard flashes of fireflies was taken in June 2009 in rural Ontario by Steve Irvine. The fireflies are mostly Photuris (greenish-yellow flashes) with some Pyractomena (orange flickers).

  • 13:42

    Special thanks to all the photographers who so generously shared their work, and to the Prezi team for pulling together this wonderful presentation.