"Previous firefly research focused on flash pattern differences between firefly species," Lewis added. "But this study is one of the first to examine how and why flash patterns differ within a species."
Cratsley, who graduated with a Ph.D. from Tufts in 2000, and is now an assistant professor of biology at Fitchburg State College, explained "fireflies have an adult life of only two weeks, and during that time all of their energy is devoted to courtship and mating. At the very most, males have only about 10 opportunities to mate, so they need to stand out in the frenzied crowd of male competitors, and communicate to females that they're worthy of consideration for mating."
In their research, Cratsley and Lewis carefully recorded male flash signals, and found that some males produced longer flashes while others produced shorter ones. They used computer-generated flashes and light- emitting diodes to simulate male firefly behavior and see which flash types the females responded to most by tracking the females' response flashes. They found that females were much more responsive to the longer light flashes.
"We were curious to know why females should care so much about the duration of any male's flash," said Lewis. "We were surprised to find that flashes appear to be a male's way of bragging about what he can offer to a potential mate."
After the lights go out and mating begins, she noted, male fireflies provide females with a 'nuptial gift' that accompanies their sperm. This gift, also known as a spermatophore, is a high-protein nutritional package that females digest and use to provision their eggs. By measuring the duration of a male's flashes and comparing them to the spermatophore size of the same males, Lewis and Cratsley discovered that the length of a male firefl
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Contact: Craig LeMoult
craig.lemoult@tufts.edu
617-627-4317
Tufts University
14-Apr-2003