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  • As a scientist, and also as a human being,

  • I've been trying to make myself

  • susceptible to wonder.

  • I think Jason Webley last night called it

  • "conspiring to be part of the magic."

  • So it's fortunate that my career as a biologist

  • lets me dive deeply into the lives

  • of some truly wondrous creatures

  • that share our planet:

  • fireflies.

  • Now, for many of you, I know that fireflies

  • might conjure up some really great memories:

  • childhood, summertime,

  • even other TED Talks.

  • Maybe something like this.

  • My seduction into the world of fireflies

  • began when I was back in graduate school.

  • One evening, I was sitting out in my backyard

  • in North Carolina,

  • and suddenly, these silent sparks

  • rose up all around me,

  • and I began to wonder:

  • How do these creatures make light,

  • and what's with all this flashing?

  • Are they talking to one another?

  • And what happens after the lights go out?

  • I've been lucky enough to answer

  • some of these questions

  • as I've explored this nocturnal world.

  • Now if you've ever seen

  • or even heard about fireflies,

  • then you'll know how magically they can transform

  • our everyday landscape into something

  • ethereal and otherworldly,

  • and this happens around the globe,

  • like this hillside in the Smoky Mountains

  • that I saw transformed into a living cascade of light

  • by the eerie glows of these blue ghost fireflies,

  • or a roadside river that I visited in Japan

  • as it was giving birth to the slow, floating flashes

  • of these Genji fireflies,

  • or in Malaysia, the mangrove trees

  • that I watched blossom nightly

  • not with flowers

  • but with the lights of a thousand — (Bleep! Bleep!) — fireflies,

  • all blinking together

  • in stunning synchrony.

  • These luminous landscapes

  • still fill me with wonder,

  • and they keep me connected to the magic

  • of the natural world.

  • And I find it amazing that they're created

  • by these tiny insects.

  • In person, fireflies are charming.

  • They're charismatic.

  • They've been celebrated in art

  • and in poetry for centuries.

  • As I've traveled around the world,

  • I've met many thoughtful people

  • who have told me that God put fireflies on Earth

  • for humans to enjoy.

  • Other creatures can enjoy them too.

  • I think these graceful insects are truly miraculous

  • because they so beautifully illuminate

  • the creative improvisation of evolution.

  • They've been shaped by two powerful

  • evolutionary forces:

  • natural selection, the struggle for survival,

  • and sexual selection,

  • the struggle for reproductive opportunity.

  • As a firefly junkie, the past 20 years

  • have been quite an exciting ride.

  • Together with my students at Tufts University

  • and other colleagues,

  • we've made lots of new discoveries about fireflies:

  • their courtship and sex lives,

  • their treachery and murder.

  • So today I'd like to share with you

  • just a couple of tales that we've brought back

  • from our collective adventures

  • into this hidden world.

  • Fireflies belong to a very beautiful

  • and diverse group of insects, the beetles.

  • Worldwide, there are more than 2,000 firefly species,

  • and these have evolved remarkably diverse

  • courtship signals,

  • that is, different ways to find and attract mates.

  • Around 150 million years ago,

  • the very first fireflies probably looked like this.

  • They flew during the daytime

  • and they didn't light up.

  • Instead, males used their fantastic antennae

  • to sniff out perfumes given off by their females.

  • In other fireflies, it's only the females who light up.

  • They are attractively plump and wingless,

  • so every night, they climb up onto perches

  • and they glow brightly for hours

  • to attract their flying but unlit males.

  • In still other fireflies, both sexes

  • use quick, bright flashes to find their mates.

  • Here in North America,

  • we have more than 100 different kinds of firefly

  • that have the remarkable ability to shine energy

  • out from their bodies

  • in the form of light.

  • How do they do that?

  • It seems totally magical,

  • but these bioluminescent signals

  • arise from carefully orchestrated chemical reactions

  • that happen inside the firefly lantern.

  • The main star is an enzyme called luciferase,

  • which in the course of evolution

  • has figured out a way to wrap its tiny arms

  • around an even smaller molecule called luciferin,

  • in the process getting it so excited

  • that it actually gives off light.

  • Incredible.

  • But how could these bright lights

  • have benefited some proto-firefly?

  • To answer this question, we need to flip back

  • in the family album to some baby pictures.

  • Fireflies completely reinvent their bodies as they grow.

  • They spend the vast majority of their lifetime,

  • up to two years,

  • in this larval form.

  • Their main goal here, like my teenagers,

  • is to eat and grow.

  • And firefly light first originated

  • in these juveniles.

  • Every single firefly larva can light up,

  • even when their adults can't.

  • But what's the point

  • to being so conspicuous?

  • Well, we know that these juveniles

  • make nasty-tasting chemicals

  • that help them survive their extended childhood,

  • so we think these lights first evolved as a warning,

  • a neon sign that says, "Toxic! Stay away!"

  • to any would-be predators.

  • It took many millions of years

  • before these bright lights

  • evolved into a smart communication tool

  • that could be used not just to ward off potential predators

  • but to bring in potential mates.

  • Driven now by sexual selection,

  • some adult fireflies

  • like this proud male

  • evolved a shiny new glow-in-the-dark lantern

  • that would let them take courtship

  • to a whole new level.

  • These adults only live a few weeks,

  • and now they're single-mindedly focused on sex,

  • that is, on propelling their genes

  • into the next firefly generation.

  • So we can follow this male out into the field

  • as he joins hundreds of other males

  • who are all showing off their new courtship signals.

  • It's amazing to think that the luminous displays

  • we admire

  • here and in fact everywhere around the world

  • are actually the silent love songs

  • of male fireflies.

  • They're flying and flashing their hearts out.

  • I still find it very romantic.

  • But meanwhile, where are all the females?

  • Well, they're lounging down below

  • surveying their options.

  • They have plenty of males to choose from,

  • and these females turn out to be very picky.

  • When a female sees a flash

  • from an especially attractive male,

  • she'll aim her lantern in his direction,

  • and give him a flash back.

  • It's her "come hither" sign.

  • So he flies closer and he flashes again.

  • If she still likes him,

  • they'll strike up a conversation.

  • These creatures speak their love

  • in the language of light.

  • So what exactly do these females consider sexy?

  • We decided to conduct some firefly opinion polls

  • to find out.

  • When we tested females using blinking LED lights,

  • we discovered they prefer males

  • who give longer-lasting flashes.

  • (Laughter) (Applause)

  • I know you're wondering,

  • what gives these males their sex appeal?

  • Now we get to see what happens

  • when the lights go out.

  • The first thing we discovered

  • is that once a male and female hook up like this,

  • they stay together all night long,

  • and when we looked inside

  • to see what might be happening,

  • we discovered a surprising new twist

  • to firefly sex.

  • While they're mating,

  • the male is busy giving the female

  • not just his sperm

  • but also a nutrient-filled package

  • called a nuptial gift.

  • We can zoom in to look more closely

  • inside this mating pair.

  • We can actually see the gift

  • it's shown here in red

  • as it's being passed from the male to the female.

  • What makes this gift so valuable

  • is that it's packed with protein

  • that the female will use to provision her eggs.

  • So females are keeping their eyes on this prize

  • as they size up potential mates.

  • We discovered that females use male flash signals

  • to try to predict which males

  • have the biggest gifts to offer,

  • because this bling helps the female lay more eggs

  • and ultimately launch more of her own offspring

  • into the next generation.

  • So it's not all sweetness and light.

  • Firefly romance is risky.

  • For the most part, these adult fireflies

  • don't get eaten because like their juveniles

  • they can manufacture toxins that are repellent

  • to birds and other insectivores,

  • but somewhere along the line,

  • one particular group of fireflies

  • somehow lost the metabolic machinery

  • needed to make their own protective toxins.

  • This evolutionary flaw,

  • which was discovered by my colleague Tom Eisner,

  • has driven these fireflies

  • to take their bright lights out into the night

  • with treacherous intent.

  • Dubbed "femme fatales"

  • by Jim Lloyd, another colleague,

  • these females have figured out how to target

  • the males of other firefly species.

  • So the hunt begins with the predator

  • she's shown here in the lower left

  • where she's sitting quietly

  • and eavesdropping on the courtship conversation

  • of her intended prey,

  • and here's how it might go.

  • First the prey male flashes, "Do you love me?"

  • His own female responds, "Maybe."

  • So then he flashes again.

  • But this time, the predator sneaks in a reply

  • that cleverly mimics exactly what the other female just said.

  • She's not looking for love: she's looking for toxins.

  • If she's good, she can lure this male close enough

  • to reach out and grab him,

  • and he's not just a light snack.

  • Over the next hour, she slowly

  • exsanguinates this male

  • leaving behind just some gory remains.

  • Unable to make their own toxins,

  • these females resort to drinking the blood

  • of other fireflies to get these protective chemicals.

  • So a firefly vampire,

  • brought to you by natural selection.

  • We still have a lot to learn about fireflies,

  • but it looks like many stories will remain untold,

  • because around the world, firefly populations

  • are blinking out.

  • The main culprit: habitat loss.

  • Pretty much everywhere, the fields and forests,

  • the mangroves and meadows that fireflies need to survive,

  • are giving way to development and to sprawl.