Figure 43.10: Defense Mechanisms and Evolutionary Arms Races (A) The harmless hoverfly (above) gains protection by mimicking a dangerous stinging wasp (below) that predators have learned to avoid. (B) Brazil nuts (the seeds of Bertholletia excelsa) are protected by extremely hard shells that most birds cannot penetrate. The evolution of beak strength in the hyacinth macaw, however, has kept pace with the nut’s hardness.