5th instar eating a 4th instar. Cannibalism is very common in A. herberti in the Sky Islands of Southeast Arizona. These flightless insects are confined to the deepest pools in rapidly-drying streams as summer temperatures wax, until the arrival of the monsoon. With hundreds or thousands of nymphs living in a single pool, competition is fierce. The stagnant water is oxygen-poor, which makes gill-breathing prey like juvenile mayflies and dragonflies scarce. In such an environment, bulk and aggression matter, and larger individuals typically overpower smaller ones. However, A. herberti has often been observed feeding on animals larger than itself, though never in a cannibalistic context.