In the animal world, females usually aren’t the ones that show off for potential suitors. But for a species of glowworm in Finland, the females that glow the brightest are not only the most fertile, but they may also be the most pursued by mates, researchers report in the October Biology Letters.
In the nocturnal Lampyris noctiluca, the wingless females use a green glow to attract flying males. Researchers set LED traps and found that males preferred brighter traps, suggesting that males are more attracted to the brightest females. The team also found that females with bigger glowing structures laid more eggs.
Since males can’t accurately judge a female’s size in the dark, the glow could be the first indication of a healthy mate, the scientists say.