Dear Tom,
I’ve heard that fireflies are decreasing in numbers, but in early August the fields south of Davenport, Iowa, were aglow with them. Why do they flash? Does the weather affect their flashing?
–Steve Pond, Chicago
Dear Steve,
Firefly numbers worldwide have declined precipitously in recent years, but the cause is unknown. All of the more than 2,000 species of fireflies have one thing in common– bioluminescence, the ability to produce visible light–but does the weather have anything to do with it? Dr. James Case at the University of California at Santa Barbara says, “Behaviorally, luminescence in fireflies functions in mating, with each species tending to have a distinct communication flash code.” The flashes enable females and males to communicate with each other in preparation for mating, and weather has nothing to do with it.
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