Natural selection is based on the struggle for survival, but sexual selection is driven by the struggle for reproductive opportunity. And sexual selection turns out to be quite a powerful evolutionary force – it’s the reason we can enjoy such melodious birdsong, extravagant peacock tails, gigantic deer antlers, and such spectacular firefly flashes!
We know that fireflies give bioluminescent courtship signals, but firefly sex goes way beyond flashing. While mating, many male fireflies give the female a spermatophore, which is an elaborate, sperm-containing package. This firefly “nuptial gift” represents a hefty male investment that’s entirely home-made: it takes several glands to manufacture each gift. Until recently, though, we’ve been largely in the dark about the composition of these mysterious gifts.