July 9, 2012

Fireflies Light Up Each Others Lives With Gifts

John Neumann for redOrbit.com - Your Universe Online

A team of biologists from Tufts University in Boston may have answered the question of what attracts fireflies to each other. Dr. Adam South, with supervision from colleague Sara Lewis, who have been studying fireflies for 20 years, used LED lights to mimic the flashes of amorous male fireflies.

In the wild, females are very picky about what males they reveal themselves to during this part of the courtship routine. Females will only “flash back” to males they are attracted to. The researchers showed one group of females artificial male flashes in patterns and durations that had been proven attractive in previous studies. Another group of females saw “unattractive” flashes.

After several minutes of the courtship flashing, males and females were paired together in miniature chambers. The biologists recorded the encounters under infrared light to see what was happening in the dark, reports Victoria Gill in Science for BBC Nature.

Their footage revealed that females were much more likely to mate with males that had larger nuptial gifts to offer. Once the males and females were together, the quality of the flashes did not seem to affect the outcome of their meeting.

South and his team found that females preferred male fireflies that brought the largest, most nourishing gift, in the form of a spermatophore: a package containing sperm and nourishment for the female.

The results have presented the scientists with a further mystery; since the spermatophore is transferred internally, it is not clear how the female uses the size of this gift to decide whether to mate with a male.

South presented the findings, saying he was surprised to discover that, “attractive flashes only seem to benefit males during the early stages of firefly courtship. Initially, flashes are important,” he explained. “[But] once males make physical contact, females switch to [this] alternative cue.”

The team study fireflies in order to fully understand the remarkable displays and sometimes bizarre behavior that has evolved in the pursuit of sex. He continued by explaining that it was “critical to study all possible episodes” in the insects´ sexual behavior, “to truly understand the reproductive ecology of [the] species”.

“If we had stopped studying the mating habits of fireflies after the flashing stopped,” he said, “we would have missed this amazingly complex and incredible story.”

The team presented their findings at the First Joint Congress on Evolutionary Biology in Ottawa, Canada.