Know your foe: synanthropic spiders are deterred by semiochemicals of European fire ants.

Many ants prey on spiders, suggesting that web-building spiders may avoid micro-locations near ant colonies or frequented by foraging ants. Here we tested the hypothesis that ant-derived semiochemicals deter synanthropic spiders. To generate stimuli, we exposed filter paper for 12 h to workers of European fire ants, black garden ants, or western carpenter ants, , and then offered select urban spiders in three-chamber olfactometer bioassays a choice between ant-exposed filter paper and unexposed control filter paper. Semiochemical deposits of , but not of or , had a significant deterrent effect on subadults of the false black widow, the black widow, , and the hobo spider, as well as a moderate (but statistically not significant) deterrent effect on the cross spider, . The deterrent effect caused by semiochemical deposits of may be attributable to the aggressive nature and efficient foraging of in its invaded North American range, exerting selection pressure on community members to recognize semiochemicals and to avoid micro-locations occupied by .