About 1% of the nests of a crab spider (Misumena vatia [Clerck 1757]) population in coastal Maine, USA, contained apparently cannibalistic individuals. These spiderlings remained in their nests over three times longer than average and attained average masses twice that of non-cannibalistic spiderlings (maximum  =  four-fold) before dispersing. Parents of the 14 cannibalistic broods came from 10 sites separated from each other by 0.5–10 km and over 23 years; thus, this behavior appears to be widespread and relatively stable, though uncommon.