Flash Signals, Nuptial Gifts and Female Preference in Photinus Fireflies

The evolution of male courtship signals such as the bioluminescent flashes of fireflies may be shaped, at least in part, by female preference for particular characteristics of the male signal. These female preferences for male courtship signals may arise as a result of the benefits of choosing males with particular traits. One possible benefit of mate choice occurs if females can use male courtship signals as an honest indicator of male nutritional contributions at mating, nuptial gifts. This paper reviews female preference for male flash characteristics in Photinus fireflies (Coleoptera: Lampyridae), and the potential for females to use male flash characteristics to predict nuptial gift quality. In Photinus firefly species with single pulse flashes females preferentially respond to flashes of greater intensity and duration. Male Photinus provide a nuptial gift to females at mating in the form of a spermatophore and flash duration serves as a good predictor of spermatophore mass for males collected early in the season. However, Photinus fireflies do not feed as adults, so spermatophore mass decreases with subsequent matings. In response, nutrient-limited females may stop preferentially responding to longer duration flashes, increasing their overall responsiveness later in the mating season as they forage for spermatophores. Therefore, the evolution of male courtship signals in Photinus fireflies is the product not only of female preference for male flash characteristics, but also the costs and benefits of female choice that shape these preferences.