Foraging advantages of mixed-species association between solitary and colonial orb-weaving spiders.

This study investigated association between solitary orb-weaving spiders and a colonial orb-weaving spider, Metepeira incrassata (Araneae: Araneidae). Spiders were sampled along transects and an index of species association showed that two of the species were associated more frequently than expected based on a null hipothesis of random co-occurrence. The potential advantages of mixed-species association were investigated by comparing prey-capture success of one of these associates, Nephila clavipes (Araneae: Tetragnathidae), when it occurs alone, in single-species groups, and when associated with M. incrassata colonies. Field observations of prey-capture success by all three of these categories of N. clavipes revealed that individuals in M. incrassata colonies captured significantly more prey than solitaries or individuals in single-species groups. The increase in prey capture by N. clavipes in M. incrassata colonies may result from utilization of a foraging niche which intercepts a diffirent spectrum of prey than that available to single-species groups or solitaries. Related to this enhanced prey consumption is greater fecundity of spiders in association with M. incrassata as compared to solitaries or individuals in single-species groups.