Fireflies Blink in Sync

Male fireflies need rhythm to find a female, although it takes something more to actually find a mate.

A new study shows that when male fireflies synchronize their flashes, it helps their female counterparts to find males of her own species among the other species of fireflies flitting about on warm summer evenings. When she sees males flashing together in the right pattern, she can then answer with her "come hither" counter flash.

"What the females are doing is looking for the number and tempo of flashes," said firefly researcher Andrew Moiseff of the University of Connecticut. That's much easier for her to see when the guys work together.

"The dialogue is that the males are flying and flashing their species-specific pattern," said Moiseff. And a female of their species on the ground sees and recognizes this flash pattern, then sends out another flash signal which says, "Hey guys! I'm one of your species, but female."

Moiseff and his colleagues confirmed this behavior by rigging up light emitting diodes (LEDs) to mimic the flash patterns of fireflies. His paper on the synchronous flashes appears in the July 9 issue of the journal Science.

"Since visual clutter increases with population density, these results also suggest that flash synchrony could be much more widespread in other firefly species," said Sara Lewis, a professor of evolutionary and behavioral ecology at Tufts University.

All this flashing is not the end of the mating game, however.

"Six to a dozen males may be attracted," said Moiseff. "We don't know if she's distinguishing among males when she responds."

When a female firefly -- which is really a kind of beetle -- ventures to give the signal, she is calling quite a crowd. In the field it's not at all uncommon to find a solitary female surrounded by a dozen hopeful males, Moiseff said. So there is yet another level of selection that is going on which researchers have yet to discover, he said.

"This is a really nifty experimental study exploring the benefits of male flash synchrony in roving fireflies," said Lewis. "The fact that female fireflies are more likely to give a flash in response to synchronous signals than to non-synchronous ones is a big deal. For a firefly male, we know that getting a female to answer him is at least half the battle to winning a mate."

Anyone who lives in an area with fireflies can experiment for themselves with a flashlight, Moiseff suggested.

"You'll typically have three to four species in your backyard," said Moiseff. If you watch carefully, you'll see the different species' flash patterns of the males in the air.

By flashing a small flashlight on the ground, you can imitate a female and sometimes get males to drop down to the ground to check out your flashlight, he said.

"These insects, like so many insects, are very complex," said Moiseff. They may have small brains, but they are capable of some amazing behaviors.