Female social spiders don’t mind being stereotyped. The 5- to 8-mm-long brown arachnids (Anelosimus studiosus, shown), which live in colonies composed of about six females in North and South America, pick jobs that best suit their personalities. Aggressive spiders are most likely to be hunters, defenders, and web engineers, researchers report online today in the Proceedings of the National Academy of Sciences, whereas docile spiders are more likely to care for young. The choices make sense, according to the study: Compared with docile spiders, aggressive spiders are more than twice as effective at capturing prey; they construct webs that last 64% longer; and they are more than eight times as likely to successfully repel intruders by chasing them off and then buffering the colony with thick, mazelike matrices of silk. Likewise, when the colony hatched dozens of offspring, the little ones survived twice as long under the docile spiders’ care; the aggressive spiders had the unfortunate tendency to mistake their progeny for food.