Many caterpillars have colorful and sometimes toxic defenses against predators, but the North American Walnut Sphinx caterpillar really knows how to startle a would-be attacker. These little guys produce high-pitched whistles that have birds diving away from them in confusion!
Fact and sketch contributed by Amelia Munson
Source: Bura, V. L., Rohwer, V. G., Martin, P. R., & Yack, J. E. (2011). Whistling in caterpillars (Amorpha juglandis, Bombycoidea): sound-producing mechanism and function. Journal of Experimental Biology, 214, 30-37. doi: 10.1242/jeb.046805