POLENECIA PRODUCTA AND ITS WEB - STRUCTURE AND EVOLUTION (ARANEAE, ULOBORIDAE)

The web of Polenecia producta is interpreted as being a modified orb w eb. The position of the hub directly upon a twig amongst irregularly p laced branches decides the web's structure. Since the radii have to be fixed in the vicinity corresponding to the local possibilities, and s ince these possibilities vary very much from case to case, a great var iety of web scaffoldings results. All of them are characterized by a l ack of symmetry. These asymmetries, for their part, prevent the produc tion of capture threads by circling around and fixing them obliquely t o the radii as do orb weavers. P. producta adapts itself to this situa tion by attaching the adhesive material along the radii. Under these c ircumstances temporary spirals, like those of orb weavers, would be wi thout function. The short pieces of such spirals present in the webs o f P. producta are interpreted as vestiges of once functional structure s. The silk deposits P. producta lays down upon the hub can, in certai n respects, be compared with stabilimenta of other Uloboridae. The rel atively late onset of web building in P. producta (instar II spiderlin gs) is related to the ontogeny of the spinning apparatus.