Orb web traits typical of Uloboridae (Araneae)

Abstract. Web designs have long been used to characterize spider taxa and to deduce the relations between them; but systematic documentation of the amount of variation in webs within and between taxonomic groups is rare. This study, based on previously published observations and new observations of 15 species in the family Uloboridae, including two genera, Octonoba Opell, 1979 and Siratoba Opell, 1979, whose webs were previously undocumented, reviews the taxonomic distribution and variation in 22 orb web traits in at least 43 species in 11 genera in uloborids. These traits appear to occur in all orb-weaving genera in which reasonable samples are available, though only small samples are available for many species. Larger samples of the webs of three species of Uloborus Latreille, 1806, two of Hyptiotes Walckenaer, 1837, and one each of Zosis Walckenaer, 1841, Siratoba, Octonoba, Waitkera Opell, 1979 and Philoponella Mello-Leitão, 1917, revealed greater intra-specific consistencies in some traits than others. Hub traits were especially consistent. Variations in three traits may represent adjustments to the size of the space in which the orb is built. “Primary” webs, which combine orb and sheet-web traits, are built by spiderlings newly emerged from the egg sac and by adult males in at least five genera of orb-weaving uloborids and may be unique to this family. Preliminary comparisons between uloborid and araneoid orbs suggest that uloborid orbs may also differ from araneoid orbs in combining several other traits.