Aposematic coloration of gregarious insects can delay predation by an ambush predator

An important hypothesis concerning the role of aggregation in the antipreda tor defense of aposematic insects is that a group projects a larger aposema tic signal to a predator. The nearly exclusive use of birds as model predat ors may be leading us to over-emphasize the importance of signal amplificat ion as an explanation for the gregarious behavior of aposematic insects. Am bush (sit-and-wait) predators such as amphibians and praying mantids make p redatory decisions relying primarily on prey movement, and secondarily on p rey size, with pre) color being less important. Therefore, we tested the in teraction of aposematic coloration and gregarious behavior in insect defens e from frogs. We offered frogs four types of mealworm prey: (1) cryptic and solitary, (2) cryptic and gregarious, (3) aposematic and solitary, and (4) aposematic and gregarious. The frogs ate aposematic and gregarious prey si gnificantly later than they ate cryptic and gregarious prey and cryptic and solitary prey. Our results support the hypothesis that aposematic colorati on in gregarious prey, but not in solitary prey, can function to produce a sufficient aposematic signal to delay attack by an ambush predator. This re sult was not due to predator learning. Hence, the antipredator benefits of aposematic coloration in aggregated prey may function in encounters with a wide range of predators, including frogs.