Leave me alone: solitary females attract more mates in a nocturnal insect

Spatial distributions of sexual competitors and potential mating partners have a large impact on sexual selection and mating systems. Typically, such effects are investigated with regard to male aggregations. However, females may also need to compete for mating opportunities. Here, we investigated consequences of clustering and rival attractiveness on female mate attraction success under field conditions in a nocturnal beetle, the common glow-worm, <i>Lampyrus noctiluca</i>. We placed dummy females of two glow intensity (attractiveness) levels either alone or in clusters of varying attractiveness compositions. We found that by displaying alone rather than in a cluster, females have a higher probability of mating and greater potential to exercise mate choice. Within clusters, females of both attractiveness levels had the highest probability of mating when having neighbours of only the less attractive type. These results show that both the presence and attractiveness of rivals can strongly influence females' mate attraction. The findings also suggest that the distribution of wild females matches better with female than male benefits. Hence, the results highlight the important links between spatial distribution of females, male mate searching and sexual selection.