A new study examines what’s behind a glowworm’s light.

Researchers have found that the brightness of a female glowworm is a signal to males about her qualities as a mate. A study published October 20 in Biology Letters says the brightness corresponds to the number of eggs she will produce. It’s a relatively rare example of females having ornamentation to attract males, says Bruce Lyon, an ecologist at the University of California, Santa Cruz. In many other species, males have gaudy ornaments, from brightly colored feathers to large antlers that help females decide who to mate with, as they indicate good health and, consequently, good genes to pass on to offspring. Female ornamentation is rarer, probably because reproduction takes more time and energy from females and they are pickier about their mates. continue