Tufts researchers shine light on firefly mysteries

In battle of the sexes, male fireflies may lie when it comes to love

This summer, in a darkened meadow west of Boston, Tufts University biologists are continuing to shine new light on the frenzied love life of fireflies. For the first time, researchers will explore the question of whether male fireflies’ flashing light – previously shown in one species to indicate superior physical and genetic quality – has evolved in another species to provide misinformation to prospective mates. In other words, are some male fireflies lying in order to find romance?

“If female mate choice is adaptive, we would expect that the more attractive males would provide females with greater material benefits and/or genetic benefits,” said Sara Lewis, associate professor of biology in the School of Arts & Sciences. “On the other hand, sexual conflict theory predicts that male signals may evolve to provide uninformative or even misleading cues about male quality.”

Funded by the National Science Foundation and a Tufts Faculty Research Award, such research may ultimately help further our understanding of human communication, signal evolution, and biomedicine.

In previous research published in 2003, Lewis and her then-doctoral student Christopher Cratsley found that female fireflies of one species (Photinus ignitus) are strongly attracted to males who give longer flashes because that signal indicates males that can provide better nutrition for their offspring. But the Tufts research team has recently found evidence suggesting that the preferred males in a related species (Photinus greeni) do not provide any such benefit.

“It’s possible that the male flash pattern may have evolved to provide misinformation,” Lewis explained. “Although males and females both try to maximize their reproductive output and contribute to the next generation, this is not necessarily a co-operative venture and conflict often arises in nature.

“For example, in Drosophila fruitflies, males’ efforts to maximize their sperm’s competitive ability have led to the evolution of chemicals produced by their reproductive glands. These chemicals kill the sperm of other males that have mated with the same female but they are also toxic to the female — hence conflict.”

In a collaborative research effort with insect physiologist and Tufts postdoctoral research fellow Dr. William Woods, Lewis is also examining other questions, such as how much energy the males’ “flashy” courtship displays require–an effort that will involve laboratory testing in tiny respirometry chambers to measure the carbon dioxide produced during flashing and resting.