Fireflyers International Network (FIN) has just announced the first-ever World Firefly Day, an annual event to raise awareness about these tiny insects and spark interest in their conservation. Their goal is to get firefly fans all over the globe to celebrate by participating in local firefly-watching festivals, education programs, art exhibits, night walks, and more. For more info, visit the FIN website here.
“Tis strange – but true; for truth is always strange. Stranger than fiction.”
– Lord Byron, Don Juan (1823)
The previous episode left our Pyractomena larva hanging – literally – doing some aerial pupation, very unusual behavior for a firefly! Forsaking the amphibious wanderings of its snail-eating childhood, the pupa now hangs quietly. But inside, a maelstrom of cellular reorganization and growth is transforming its larval body. In just a few weeks, it will emerge as an adult firefly. At this next stage, our Pyractomena will have only one thing on its mind: sex. And yup – you guessed it: Pyractomena fireflies have strange sexual habits, too!
Most male lightningbugs fly & flash to win females. But after racing to emerge early, Pyractomena borealis males forcibly mate with their child brides! Continue reading
We’ve already heard (previous post) about the weird hunting habits of Pyractomena larvae – they’re amphibious. So let’s continue our Pyractomena tour, moving along to consider another strange behavior: they pupate en plein air!
Once they’re ready to metamorphose into adult fireflies, the larvae of most North American lightningbugs seek safety underground. Immobile, they huddle for weeks in soil chambers, finally emerging to light up our skies as adult fireflies. But no cold dark cellars for Pyractomena fireflies! Instead, these strange fireflies climb up onto vegetation to undertake a feat known as aerial pupation.
If you’ve been paying some attention, you probably already know that here in North America, we’ve got several different kinds of lightningbug fireflies. Those in the genera Photinus and Photuris are common and relatively well-studied. But the Pyractomena lightningbugs – also pretty common – are a black box. We know so little about them! And more’s the pity because Pyractomena have a pretty bizarre lifestyle, making them quite a bit different from our other fireflies.
So here’s the first taste of Pyractomena strangeness: these amphibious larvae are snail-eaters! Continue reading
Autumn happens to be quite an exciting time for fireflies. But, yeah I get it – you probably can’t imagine fireflies beyond summer. After all, that is when adult get all reproductive and stuff. But there’s cryptic chapter in the firefly’s life story, and it’s starting right now.
Once mated, the female firefly will produce 30-100 eggs, laying them one-by-one in some moist dirt or moss. After a few weeks, these eggs hatch out into tiny larvae that immediately burrow down underground. Though adult fireflies only live a few weeks, their progeny will spend up to two years hanging out underground.
Baby fireflies happen to be voracious predators. They’re constantly on the hunt for earthworms, snails, and any other soft-bodied prey. They attack creatures that are much bigger than themselves. How do they manage this? First, they use their sharp, sickle-shaped jaws to inject the prey with paralyzing neurotoxins. Next, they secrete digestive enzymes to liquify their prey, then they slurp it up. Earthworm smoothie, anyone?
When they’re disturbed, larval fireflies glow from two tiny lanterns located at the tip of their abdomen. All firefly larvae can light up, across 2000+ species, even when the corresponding adults cannot. So we think fireflies’ light-producing talent first evolved because it gave these juveniles some advantage.
But … what’s the point of these juveniles being so conspicuous?
We know that fireflies contain nasty-tasting chemicals that help them avoid getting eaten (see earlier post). Lots of poisonous creatures use bright coloration to warn off potential predators. Yet firefly larvae are mainly active at night or underground, where having bright colors would be futile. But a flash in the darkness would certainly do the trick – like a neon sign, it blazes out “I’m toxic – stay away!”
So get ready to watch for firefly larvae crawling along roadsides and wooded paths, glowing dimly. Often overlooked, these juveniles should rightly be celebrated as the original inventors of fireflies’ magical lights.
OK, I’ve learned a lot about Twitter hashtags. For instance:
#firefly will usher you directly into the great TV series Firefly, a sci-fi cult classic that Fox inexplicably cancelled after just one season. The story centers on the crew of Serenity, a Firefly-class starship (because tail section lights up on take-off). Premiered on Fox in 2002, the show featured a smart script, terrific ensemble acting, heartthrob Nathan Fillion, and a great theme song. In spite of all this, and to the eternal dismay of its many loyal fans, the show went extinct after just a single season. Yet it lives on in the Twitterverse.
Meanwhile, #fireflies yields an endless stream of tweets and Youtube remixes posted by fans of the song “Fireflies” by Owl City. Topping the US and Canadian charts in 2009, this song ties together insomnia, fireflies and summer. Most frequently tweeted are these lyrics: Continue reading
Recently I’ve learned via Twitter that lots of cats (dogs, too) enjoy chasing after fireflies. But please don’t let your pets eat the fireflies! This is for their own sake, not for the fireflies.
Living in a world full of insect-eating predators, fireflies have evolved potent defenses to protect themselves. Firefly blood carries a bitter-tasting and toxic chemical called lucibufagin (lucifer = Latin for light bearer + Bufo = toads that produce similar chemicals).
Lucibufagin (often nicknamed LBG) makes a powerful poison because it is effective against almost any animal. It binds to and disables an enzyme, known as the sodium-potassium pump, that’s essential for all animal cells. This enzyme actively transports ions across cell membranes, generating an electrical potential that allows us to do really important things like think and move our muscles. To protect themselves, many plants and a few animals have converged on stocking similar toxins in their chemical arsenal.
Every June, fireflies light up the Smoky Mountains with their exuberant courtship displays – sure, it all seems very romantic. But a few years ago I spent some weeks with colleagues studying the predators that take advantage of these dense breeding aggregations. We knew that certain insectivores – like birds and lizards – avoid eating fireflies because they’re toxic. So we didn’t expect to find many predators enjoying this luminous feast. Little did we realize how gore-filled that summer would turn out to be!*
* You can read our Dark Side paper here: Lewis, S.M., L. Faust, and R. De Cock. 2012. The Dark Side of the Light Show: Predators of Fireflies in Great Smoky Mountains. Psyche, 634027.
People often ask me this excellent question. Yet it doesn’t have a quick or easy answer. One reason is that different species live in different habitats. For instance, the salt marsh firefly Micronaspis floridana is restricted to intertidal regions along the Florida coast. Another reason is that certain things matter to adult fireflies, whereas different things matter to the juveniles.
For adult fireflies, what’s most important is finding a dark place for their courtship displays. Artificial lights – streetlamps, outdoor security lights, even car headlights – can disrupt firefly courtship conversations. Such bright backgrounds make it difficult for fireflies to see each other’s courtship signals. Another desirable habitat feature for adult females is easy access to suitable egg-laying sites, like moss, moist soil, or decaying wood.