Ask Sam: Are There More Fireflies This Summer?

Jul 27, 2018

Hey little guy. How are you doin?
Credit Flickr Creative Commons | blueskyfantasie

Every other Friday on Morning Edition NHPR’s Sam Evans-Brown tracks down answers to questions about the outdoors for our listeners in a segment we call “Ask Sam.” 

Christopher from Bradford, Vermont, asks: “I saw something today that I haven’t seen ever — I think — driving home tonight. I have never seen so many lightning bugs as I’ve seen tonight. I mean, literally thousands of lightning bugs on either side of interstate 91 in the grassy area. And I’m wondering, why am I seeing that now? Why all the sudden am I just noticing thousands of lightning bugs in this area?”

Ah, fireflies. The most charismatic of the bugs. Who doesn’t get all starry-eyed after seeing a field full of fireflies?

To answer this question, I reached out to Professor Sara Lewis of Tufts University, who laid down some basic firefly life-history knowledge. Just in case you’ve never seen one up close and in the light, fireflies are beetles, but that’s really only the end of their life.  Most of the 2,000 or so different species of fireflies spend as much as two years as a larva in the ground, where — yes — they still glow. (except you’ve probably never seen them, because as Sara says, “when was the last time you were digging in your garden at night?”)

Just like other things that live in the soil in New England, firefly larvae like it when things are moist, and while the headlines have mostly been about drought conditions in the state, lately, our weather memories are relatively short. “Last fall we had pretty wet conditions, and this spring we had wet conditions,” says Sara. In theory this could be leading to what would seem like a very firefly-ful year.

Though we should mention that we don’t actually know that there are more lightning bugs this year, because there isn’t a great census of firefly populations. Instead we have anecdotes from listeners who call me or email Sara Lewis saying, “there are a lot of fireflies this year!” If you’d like to help remedy that problem, Massachusetts Audubon is getting a citizen science effort going, so you can spend 10 meditative minutes a week counting fireflies in your yard FOR SCIENCE!

So that’s a pretty straightforward answer. Can I blow your mind with some firefly facts, now?

My favorite is that most fireflies, like most moths, don’t eat. They’re only a winged insect for a few weeks or months, and during that whole time, they’re living on the calories stored up as a vicious, voracious larva. That whole time as a beetle they’re just trying to reproduce — essentially gonads with wings.

This doesn’t mean that there is zero exchange of nutrients, though. When they mate, males give females “a really fancy, beautiful, coiled nuptial gift,” says Sara Lewis, “It’s exactly what it sounds like: it’s a mating gift. It’s packed with protein and other stuff.”

Now there’s a very notable exception to the no mouth-parts general rule. There’s another sub-family of fireflies, the photuris fireflies, who have been dubbed by researchers as the firefly femme-fatales. The females of these lightning bugs lure in unsuspecting males by mimicking the patterns of flashes that each species uses. When the hapless male gets close enough, she seizes him and sucks him dry. This provides the female photuris with more than just a meal, it’s her only source of lucibufagins, the defensive compound that makes other fireflies a bad meal to predators.

That should give you something to think about everytime you drive down a lightning bug speckled stretch of I-91. It's not just a light show out there, it's love and life, deception and death. What a drama!

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