Quantitative analysis of orb web patterns in four species of spiders.

The orb webs of the four species Araneus pima (species nova), Araneus diadematus (Clerck), Argiope aurantia (Lucas), and Neoscona domiciliorum (Hentz) built under controlled laboratory conditions were compared and evaluated quantitatively at two different points in the life cycle in regard to size, regularity, shape, and fine structure. Orb webs of two species from one genus can be distinguished, but are more alike than webs from different genera. Mature spiders built highly specific webs, a fact which may play a role in species isolation during courtship. In adults, web measures correlated in size with the spiders' taxon; young spiders' web size measurements corresponded rather to their body weight or leg length. A web's regularity seemed to be closely related to age. Adult and young spiders built oval-shaped webs with eccentric hubs. Mesh width was correlated with leg length at both age levels. Web data support the likelihood of a monophyletic evolution of the four species.