Title: A Comparison of Capture Thread and Architectural Features of Deinopoid and Araneoid Orb-Webs
Author: Brent D. Opell
Abstract: Orb-webs constructed by the superfamilies Deinopoidea and Araneoidea share a common architecture, but differ in both their orientation and the type of capture thread that they contain. This study uses transformational analyses to determine which web features these clades share and which features are unique to the Araneoidea and may be associated with changes in web orientation and capture thread composition. It examines relationships among spider weight, the cross sectional area of capture thread axial fibers, and features of orb-web architecture in four species of the Family Uloboridae that construct horizontal orb-webs containing cribellar thread and four araneoid species that construct vertical webs containing adhesive capture thread. In both groups, spider weight was positively related to web area and the number of radii in a web were positively related to the number of spirals. In uloborids, weight was negatively related to the number of spirals per web area and axial fiber cross sectional area was positively related to the number of radii per capture spiral turn. In araneoids, spider weight was positively related to axial fiber cross sectional area. The number of radii per capture spiral turn was greater in uloborid webs, and the weight-specific axial fiber cross sectional area was greater in araneoid webs. Many of the features that distinguish araneoid orb-webs appear to equip them to absorb the greater forces of prey strike that are associated with a vertical orb-web orientation.