Costly mating delays drive female ornamentation in a capital breeder

How fecundity might be traded off with mate attraction and other aspects of reproduction in females remains poorly understood. We investigated these allocation trade‐offs using the common glowworm ( Lampyris noctiluca ), a lampyrid beetle, in which flightless, sedentary females only use resources gathered during the larval stage to attract flying males by glowing. While sexual signaling was not found to have a significant fecundity cost, a delay in successfully attracting a mate greatly increased the risk of reproductive failure, with fecundity losses being more severe in small females. These findings are among the first to show that failure to quickly attract a mate can decrease female fecundity. The results also show how the length of delay before mating can drive the evolution of female sexual ornamentation.