Ants Co-Occurring with Predatory Antlions Show Unsuccessful Rescue Behavior towards Captured Nestmates

The interaction of antlions and ants is postulated to be a predator-prey interaction in which the involved parties coevolve. Here, we investigated two issues of potential significance in terms of antlions and ants imposing selective pressures on one another. First, we determined whether trap-building antlions and sand-dwelling ants closely co-occurred in an area inhabited by both. In the field, we found that ants were the main potential prey items in artificial traps placed inside aggregation zones of antlions and that Formica cinerea workers comprised the majority of these ants. Second, we checked whether rescue behavior, a type of prosocial behavior displayed by F. cinerea workers and performed towards nestmates captured by antlions, reduced the hunting success of the latter. In the laboratory, we found that rescue attempts were very rarely successful. Overall, caution must be used when considering the coevolution of antlions and ants. Clearly, even though these two organisms can closely co-occur, the rescue behavior of ants seems to be unrelated to the predatory threat from antlions.