Body-colour variation in an orb-web spider and its effect on predation success

Abstract

Animal body coloration serves several functions such as thermoregulation, camouflage, aposematism, and intraspecific communication. In some orb-web spiders, bright and conspicuous body colours are used to attract prey. On the other hand, there are other species whose body colour does not attract prey. Using a spider species showing individual body-colour variation, the present study aimed to determine whether or not the variation in body colour shows a correlation with predation rates. We studied the orb-web spider (Cyclosa argenteoalba) using both field observations and T-maze experiments, in which the prey were exposed to differently coloured spiders. Cyclosa argenteoalba has silver- and black-coloured areas on its dorsal abdomen, with the ratio of these two colours varying continuously among individuals. The bright and conspicuous silver area reflects ultraviolet light. Results of both field observations and colour choice experiments using Drosophila flies as prey showed that darker spiders have a greater chance of capturing prey than silver spiders. This indicates that body-colour variation affects predation success among individuals and that the bright silver colour does not function to attract prey in C. argenteoalba.