The pattern of prey utilization of the orb-weaving spider
Araneus pinguis was studies by comparing between arthropods restrained in the empty webs (spiders were removed) and those unattacked in the
intact webs (spiders were not removed). The number of arthropods was larger in the empty webs than in the intact webs. In
the empty webs, web area, mesh width, number of radii, and signal thread length were presumed to affect the number of arthropods
left in a single web. As for the intact webs, web area, mesh width, and web-exposure time were important factors. In the empty
webs, the density of arthropods decreased away from the hub. On the other hand, the density of unattacked arthropods in the
intact webs was the same throughout the web.
Arthropods in the empty webs were larger than those in the intact webs. The upper limit in size of unattacked arthropods increased
along with the distance from the hub in the intact webs, but not in the empty webs. These results indicate increase in the
minimum size of eaten arthropods increased in the former. This positive sizedistance relation may have resulted from the adaptive
switching of spiders’ alternative foraging methods (i.e., the rapid attack at encounter and the later eating during web deconstruction)
on the basis of the prey profitability.