Using ants to understand evolutionary arms race.

Professor of Psychology and Education Karen Hollis doing field research on ant behavior.

By Keely Savoie

In a review article for Psychological Science Agenda, Mount Holyoke College Professor of Psychology and Education Karen Hollis outlines her research showing that context, learning, and experience all contribute to an endless high-stakes arms race between ants and antlions where the ultimate prize is survival.

In the piece—submitted at the invitation of the monthly e-newsletter of the Science Directorate of the American Psychological Association—Hollis explains that sand-dwelling ants face numerous threats in their lives, not the least of which is the predatory antlion. They make conical pits in loose sand and lie in wait for hapless victims to fall in.

To combat such losses, ants have evolved a series of “rescue behaviors” to deliver victims from the antlion traps by digging them out, pulling their limbs, and biting at whatever restrains them. Antlions, on the other hand, have evolved learning behaviors to ready themselves for capture in response to the vibrational cues of prey.

In one experiment, Hollis and colleagues demonstrated that ants will perform rescue behaviors, but only in response to chemical “calls for help” from their own nestmates. Hollis also found that ant species that do not live in sand—and are not preyed upon by antlions—would perform similar behaviors, but ineffectually. This suggests that the behavior evolved in a common ancestor, but is not well preserved in species where it does not confer a survival advantage.

In another experiment, Hollis showed that antlions were capable of learning cues that prey delivery was imminent—and would respond to such cues by readying themselves for attack. The antlions that learned such cues grew to maturity much faster than those that did not, indicating that the ability to learn from cues conferred a selective advantage.

Together, these adaptations and counter-adaptations represent what is known as the ”Red Queen Effect”—running faster and faster to stay in the same place.

Each month, Psychological Science Agenda features an invited article by a leading-edge scientist. These articles are read by psychologists, students, academic administrators, journalists, and policymakers in Congress and federal science agencies.

Read the full article about Hollis’s research here.