The convergent development of orb-webs in cribellate and ecribellate spiders

Abstract

Orb-webs are highly developed and can be understood as the best technical solution of the problem how to place capture-threads in the most efficient and economical way. They are built by cribellate and ecribellate spiders. Phylogenetical relations between some families of Cribellate and Ecribellate cannot be ignored, but for some important reasons it is difficult to imagine that on the level of orb-weaving cribellate spiders became ecribellate by reducing the cribellum. Thus, these specialised webs must have developed on both sides independently and are the result of a convergent evolution. Steps leading from primitive use of threads for capturing insects to the typical and latter modified orb-webs of Cribellate and Ecribellate can be discerned. © 1972 by the American Society of Zoologists.