Swarming Locusts in the United States
Grasshoppers in the genus Schistocerca are commonly known as the swarming locusts.
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Recent research suggests that Schistocerca species found in the United States descend from desert locusts that crossed the Atlantic Ocean some three to five million years ago.
Schistocerca in the United States often go by the name of bird grasshoppers because of their relatively large size and ability to fly. They are not the only grasshoppers capable of flight, or capable of causing severe habitat or crop destruction. However, they are known to cause considerable agricultural destruction in their range.
Generally, though not always, they can be identified by the presence of a dorsal stripe. The White-lined Bird Grasshopper (Schistocerca albolineata) in the top picture is native of the desert Southwest and is characterized by a light yellow dorsal stripe.
More Schistocerca research published in the Annals of the Entomological Society of America lists ten different native Schistocerca species. With the exception of the wide-ranging Spotted Bird Grasshopper, all have more limited geographical range.
Scientists are also currently investigating comparative swarming behaviors between species. Most agree that swarm behavior is not a dominant characteristic of any United States species. The article To be or not to be a locust? A comparative analysis of behavioral phase change in nymphs of Schistocerca americana and S. gregaria concludes, "Comparison with S. gregaria revealed that the magnitude of density-dependent behavioral change, particularly among final instar nymphs, was much reduced in S. americana."
Despite their comparatively less pronounced swarming behavior, American bird grasshoppers (Schistocerca americana) do exhibit density-dependent phase polyphenism. Their range is usually described as limited to the Southeast, however, at least one has been spotted as recently as October 2007 in Queens, NY.
© 2001. Patricia A. Michaels