Test of the prey-attraction hypothesis for the scorpion fluorescence

A striking feature of most scorpion species is fluorescence under ultraviolet light, but few studies have investigated the adaptive benefit of this trait. A hypothesis is that fluorescence may lure prey towards the scorpion improving foraging success. In this study, we investigated whether the fluorescence of the scorpion <i>Centruroides granosus</i> Thorell, 1876 lures the house cricket <i>Acheta domesticus</i> Linnaeus, 1758. We performed two experiments: 1) an arena in which crickets were exposed to both fluorescing and black-painted non-fluorescing scorpions and 2) a tunnel in which crickets could walk out through one of the two exits, each with a scorpion treatment. None of the experiments provided evidence that the scorpion fluorescence is attractive to house crickets since they did not show preference for any of the two scorpion types. Variables such as cricket sex or scorpion sex did not influence their response towards the fluorescence; however, crickets were on average closer to male scorpions in the outdoor arena and closer to female scorpions in the laboratory arenas. Moreover, male crickets were more active than females in the tunnel experiment, in line with the results of the arena experiment showing that male crickets were on average closer to the scorpions in the laboratory. We discuss potential implications and suggest that more experimental work is required to investigate potential adaptive benefits of the scorpion fluorescence under various biotic and abiotic factors.