PREDATION ON DISPERSING MISUMENA-VATIA SPIDERLINGS AND ITS RELATIONSHIP TO MATERNAL FORAGING DECISIONS

Misumena vatia (Thomisidae) spiderlings leaving nests guarded by their mothers experienced lower predatory pressure than those leaving unguarded nests. However, this relationship was independent of the size of either their mother or brood, traits affected by differences in maternal foraging success. The principal spiderling predator at this stage, the small salticid spider Metaphidippus insignis, hunted about unguarded, but not guarded, nests. Even the smallest Misumena mothers, being much larger than Metaphidippus, effectively guarded against the salticid, quickly driving it from their nests. This nonselective predation on the spiderlings, combined with the superior success of large broods exposed to parasitism by ichneumonid wasps, demonstrates that highly successful female Misumena foragers enjoy marked fitness advantages, at least through their offspring's dispersal from the nest. It supports the basic, though seldom tested, assumption of optimal foraging theory that success in foraging translates into enhanced lifetime fitness.