Orb-web, no web: unusual mating behaviours in an orb-web spider

The evolution of the orb-web was associated with a major radiation in
spider diversity. The major functions of orb-webs are prey capture and as
substrates for courtship and mating. However, the use of orb-webs has
associated costs, and the modification and loss of orb-webs has evolved
multiple times. While variation between species is evident, such as
reductions in or loss of the orb-web for foraging, this kind of variation
within species is rarely seen. Here, I describe laboratory observations of
foraging and mating without an orb-web in a typical orb-weaving spider,
the Australian garden orb-weaver (Hortophora biapicata). I discuss these
behaviours, which are likely cases of opportunistic plasticity, in an
ecological and evolutionary context. Further investigation of these rare
and unusual behaviours may provide unique insights into the function and
origin of important traits associated with the orb-web, and the evolution
of extended phenotypes.