The locust that is causing so much devastation to crops in Eastern Africa, Pakistan, India and other Middle Eastern countries is the desert locust, Shistocerca gregaria. We don’t have desert locusts here in the US, but we do have American bird locusts, Schistocerca americana. American bird locusts, a.k.a. American grasshoppers, are similar to desert locusts in appearance and general biology, but American bird locusts never enter a plague level, migratory phase, like desert locusts. Although they eat a wide variety of plants, American bird locusts are rarely numerous enough to cause serious damage here in Mississippi, and when they do, it is usually in combination with other grasshopper species.
These are large, showy grasshoppers with females exceeding two inches in length. They earned the “bird locust” part of their name because of the way they fly. If you flush an adult while walking through a field, they are not going to just hop a few feet away. Instead, they may fly several hundred feet before landing in a tree. Most other grasshoppers overwinter as eggs in the soil, but American bird locusts overwinter as adults. There are two generations per year, with numbers being highest in the fall.
We used to have a “plague locust” here in the US, but not anymore. Early settlers of the western US were periodically devastated by huge outbreaks of Rocky Mountain locusts, Melanoplus spretus. The numbers of grasshoppers occurring during these outbreaks is difficult to comprehend. Firsthand reports often told of swarms that darkened the noon day sky. In 1875, Dr. Albert Child documented a swarm of Rocky Mountain locusts that took five days to fly over his location in Nebraska, flying at approximately 15 miles per hour. By telegraphing other towns in the area he determined this swarm to be at least 110 miles wide, and, by using a telescope and his meteorological training, he estimated the swarm for grasshoppers flying overhead to be ¼ to ½ mile thick. Estimates of the number of locusts in this swarm range from 3.5 to 12.5 trillion.
The damage such huge numbers of hungry grasshoppers can cause is even more incredible. Devastated farmers reported whole fields of corn being completely consumed, stalk and all, in as little as three hours. “They ate everything but the mortgage!” was one of the more memorable quotes used to describe the aftermath of a locust swarm.
How could an insect go from these kinds of numbers in 1875 to being extinct by 1902?
The book referenced below provides the full story, but the short answer seems to be that as settlers continued to move west and put more and more land to the plow they inadvertently destroyed habitats where these locusts lived and bred when they were not in plague stage.
In other words, it happened by accident!
See past issues of the Bug’s Eye View newsletter for information on two other grasshoppers common to Mississippi: Carolina grasshoppers and pygmy grasshoppers .
For more information on the Rocky Mountain locust, its impact on the western US and why it went extinct, see the book, Locust: The Devastating Rise and Mysterious Disappearance of the Insect that Shaped the American Frontier by Dr. Jeffery Lockwood.
Blake Layton, Extension Entomology Specialist, Mississippi State University Extension Service.
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