To get the female fireflies in the mood, the researchers relied on LED lights programmed to make two kinds of flashes. Some females saw only artificial male flashes determined by previous research to be highly attractive to females; others saw unattractive flashes.
Male fireflies were also split into two groups: virgins whose nuptial gifts were large since the males had never mated and males whose spermatophores were smaller because they had mated the previous night. After several minutes of courtship flashing, males and females were put together in pairs, and the Tufts biologists videotaped their close-up courtship behaviors under infrared illumination. Because they take place under cover of darkness, many of these behaviors had never before been observed.
Analysis of hours of firefly video revealed that once a female was in close quarters with a male, she was much more likely to mate with males that had larger nuptial gifts to offer, as determined by the researchers' later examination. The females didn't seem to care what kind of male flashes they had seen.
"We were surprised to discover that attractive flashes only seem to benefit males during the early stages of firefly courtship," said South. "Initially, flashes are important. Female fireflies preferentially respond to males based on temporal flash characteristics. Once males make physical contact, however, females switch to an alternative cue -- one that's related to male nuptial gift size. What makes this especially intriguing is that females have no way to directly evaluate gift size, since it's created and transferred internally."
Furthermore, when females mated sequentially
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