Fireflies and Mating Behavior

Carl Zimmer has an interesting article on a firefly researcher, Sara Lewis, in today's NY Times. She has been studying firefly mating behaviors for the past 25 years. Fireflies, also known as "lightning bugs," communicate with potential partners using the light displays we know so well.

The more Dr. Lewis watched firefly courtship, the clearer it became that the females were carefully choosing mates. They start dialogues with up to 10 males in a single evening and can keep several conversations going at once. But a female mates with only one male, typically the one she has responded to the most....

If females preferred some flashes over others, Dr. Lewis wondered why those preferences had evolved in the first place. One possible explanation was that the signals gave female fireflies a valuable clue about the males. Somehow, mating with males with certain flash patterns allowed females to produce more offspring, which would inherit their preference.

It is possible that females use flashes to figure out which males can offer the best gifts. In many invertebrate species, the males provide females with food to help nourish their eggs. Dr. Lewis and her colleagues discovered that fireflies also made these so-called nuptial gifts — packages of protein they inject with their sperm....

Receiving nuptial gifts, Dr. Lewis and her colleagues have shown, can make a huge difference in the reproductive success of a female firefly. “It just about doubles the number of eggs a female can lay in her lifetime,” she said. One reason the effect is so big is that fireflies do not eat during their two-week adulthood. A slowly starving female can use a nuptial gift to build more eggs.

There is much more about Lewis's research and firefly behavior at the link. One of the more interesting details is that there is at least one species of firefly that preys on other firefly species. It tracks potential prey by their flashes, and the types of flashes most attractive to females are also most likely to draw the predator's attention.

I have become more interested in fireflies since enrolling in the Firefly Watch sponsored by the Museum of Science in Boston. Firefly Watch is a citizen science program that asks participants to spend ten minutes once a week recording the flashing behavior of fireflies in their yard or other habitat. So far I have only noted one flash pattern among the fireflies in my neighborhood – a single, yellow-green flash repeated at regular intervals. Based on the appearance of the fireflies I see in daylight, I think these probably belong to the Photinus genus.