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Cannibal Fireflies Are The Femme Fatales Of The Lightning Bug World

By Justin Breen | August 10, 2016 5:33am | Updated on August 10, 2016 5:37pm
 A lightning bug on a human hand. The insects are in decline in parts of the world due to habitat loss.
A lightning bug on a human hand. The insects are in decline in parts of the world due to habitat loss.
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Flickr Creative Commons/KimOnline

CHICAGO — There are many misconceptions about fireflies, starting with the fact they're flies at all.

Fireflies, or lightning bugs, are in reality beetles, and there are more than 100 species of the insects flying around Chicago right now for the next few weeks.

Their flash of "fire" light produces a bright yellow color, but no heat, and it serves several purposes, not just to attract a mate. That's according to Doug Taron, curator of biology at Peggy Notebaert Nature Museum, who's been fascinated with the bugs since he was a little kid.

"Fireflies are wonderful creatures," Taron said of the bugs, which make a chemical cocktail with a light-producing organ in their abdomen.

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The insects' light flash is not just a single strobe. Species — there are 136 in North America — are differentiated using high-speed cameras to watch each flash, which actually contains a super-fast pattern of flashes.

The bursts of light also purposes as a warning to other bugs who might want to eat them and, perhaps surprisingly, are used by some firefly females to draw other species of the bugs to them. In those cases, the male bugs aren't being used for mating; they're being eaten by the females, Taron said.

 There are more than 100 species of fireflies in North America. The bugs are actually beetles, and some female species eat the males of other species.
There are more than 100 species of fireflies in North America. The bugs are actually beetles, and some female species eat the males of other species.
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Flickr Creative Commons/Chris Potako

"They're called femme fatale females," he said. "They're sort of cannibals, but they don't eat their own species, just other species."

Firefly Femme Fatale from Nature Documentary on Vimeo.

Other fireflies might be the only thing lightning bugs eat during the month to month and a half as adults. When they're larvae, they dine on earthworms, potato bugs and other things that live near or just below leaf litter.

If you think of putting plant life in a jar filled with the fireflies you catch has a purpose, think again. Fireflies won't eat whatever's in there, and they don't lay eggs on leaves, grass and other shrubbery either. They lay their eggs in moist soil, Taron said.

Fireflies can be seen all over the city, even Downtown, but they prefer spaces with lawns that aren't heavily manicured, Taron said.

If you want fireflies in your yard, try to leave little corners of your lawn less manicured, Taron said.

"That will provide a home for things the larvae like to eat," he said.

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