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Fewer Fireflies?

A summer emblem grows scarce

by Jeff Mortimer

posted 8/6/2009

"Suddenly, they're not there," says Scio Township resident Eleanor Lord.

When Lord and her husband, Tony, immigrated to the United States four years ago, they were delighted by the nightly display of fireflies, the beguiling beetles who decorate summer yards with their bioluminescent mating signals. "We don't have them in the U.K.," she says. "They're just magical. We saw a lot in our garden that first year." But this year, she says, "we sat on our deck for something like three hours the other night and saw four."

"There used to be lots of fireflies," agrees Arsenio Ablao, a Pauline Boulevard resident, "but not lately. I don't see them much anymore."

What's going on? It's not clear.

"They seem to be fine at my house," says Mark O'Brien, insect collections manager at the U-M Museum of Zoology. "All insects have population fluctuations, and what may seem to be a dearth of one species in one area may only be a blip."

In fact, along much of the East Coast, some say this has been the best summer in memory for fireflies--perhaps because of rainy weather.

But Jim Lloyd, a University of Florida professor who has studied fireflies for almost half a century, is convinced they're declining. "Everything that I've seen down here in Florida and as I've traveled around the country indicates there aren't anywhere near as many as there used to be," he says. "Over the past thirty-five years, I've seen fewer and fewer and fewer."

Possible causes, Lloyd says, are increased artificial light, which makes it harder for the romantically inclined to find each other; a lowering of water tables from pumping groundwater, which reduces the number of snails and earthworms that firefly larvae feed on; and habitat loss.

The latter might be the most likely suspect in the case of Photinus marginellus, the type of firefly that seems to be the most common in Ann Arbor. Of the nearly 200 firefly species in North America, they are among the poorest fliers

...continued below...


and thus highly site-specific. If the patch of ground they inhabit is wiped out, so are they. But this doesn't explain the decline in the Lords' yard, which remains a great firefly habitat. So maybe it's just that we had an unusually cool June and July this year.

What's a firefly lover to do? Minimize outdoor lighting. Forgo pesticides and bug zappers. Leave some deadwood in the yard for larva habitat. It is, admittedly, not much.

"We've just made it hell for fireflies and everything else," Lloyd says. "It's not like they can pack up and leave. They die out."    (end of article)

[Originally published in August, 2009.]

 

 
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