Foraging Behavior of Crab Spiders (Misumena vatia) Hunting on Inflorescences of Different Quality

Crab spiders (Misumena vatia) given the choice of hunting at milkweed inflorescences (umbels) bearing 25 + or 5-10 nectar-producing flowers (high quality and middle quality, respectively) selected high-quality umbels about two-thirds of the time and middle-quality ones about one-third of the time. They attacked similar proportions of insect prey visiting these two kinds of umbels, even though highquality umbels attracted three times as many prey as middle-quality ones. Spiders captured significantly more prey on high-quality umbels than on middle-quality ones, but no more than predicted by the number of insects. On both types of umbels, attack distances were shorter than distances eliciting orientation or no response at all from the spiders. Minimum distance to prey gave the best prediction of whether a spider would attack.