ChriKo [creativecommons license] via Wikimedia Commons
Desert locusts (Schistocerca gregaria) normally shun other locusts, but in certain circumstances, such as drought conditions when resources are scarce, they are forced to be in close proximity with each other. Crowding triggers an extreme change in behavior: locusts enter a gregarious state and become strongly attracted to the company of other locusts. This switch can lead to the formation of crop-devastating locust swarms.
Lab Anim. (NY) 44, 44 (2015).
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