Ontogenetic variation in the predatory behavior of the orb-weaver spider Azilia histrio: detecting changes in behavioral organization

Abstract

Spiders in different ontogenetic stages vary in their predatory behavior. The more advanced the development of an individual, the more similar is its behavior to that of the adult. Studies have shown that the behavior of subadult and adult spiders are similar, but the similarity may be superficial, since the analytical approach usually adopted cannot evaluate important features, such as the organization of the foraging system. Systems are characterized by a modular organization, which needs appropriate analytical approaches to be properly evaluated. We tested whether there is a difference between the predatory sequences of adult and subadult spiders (Azilia histrio) and identified the most appropriate methodological procedure for the characterization of this difference. We used multivariate analysis, contrasting an approach that focuses on frequency of behavioral categories, taken independently, with an approach that directly evaluates the sequential organization of behavioral categories, thus allowing the analysis of the structure of the foraging system. While the independent variables approach did not show differences between ontogenetic stages, the organizational analytical approach resulted in a number of important differences between the ontogenetic stages. We describe the foraging system for the first time in the genus Azilia, while discussing hypotheses for the observed organizational change.