PREY CAPTURE BY THE CRAB SPIDER MISUMENA-CALYCINA (ARANEAE, THOMISIDAE)

Crab spiders M. calycina (L.) in pasture rose Rosa carolina flowers regularly attacked bumble bees, smaller bees and syrphid flies that visited these flowers. Attacks reached a maximum rate of over 20/h during mid morning, but only 1.6% of the most important prey item, bumble bees, were captured. The next most important food source, the most frequently taken item, syrphid flies Toxomerus marginatus (Say), were captured in 39% of the attempts. Since these flies have a biomass only 1/60th that of bumble bees, they comprised a much less important food source than did bumble bees. Spiders would obtain over 7% more food by specializing on bumble bees than by attacking all insect visitors, and as much as 20% more food at certain times of the day. They did not show a tendency to specialize at any time.