In a continuation of our grasshopper-focused Online Bug Encounter, I want to dive a little deeper into the life history of the now-extinct Rocky Mountain locust, Melanoplus spretus.
For those of you that are unable to tune in (or just want the quick rundown of the differences between grasshoppers and locusts), it’s important to keep in mind that all locusts are grasshoppers, but not all grasshoppers are locusts.
Locusts belong to the family Acrididae (short-horned grasshoppers), and are most famously known for their ability to wipe out crops and form plagues of, well, biblical proportions. But locusts don’t spring forth from their eggs intent on wreaking havoc on the agricultural industry. For the most part, these insects are solitary, and only swarm under specific environmental conditions.
When these species of short-horned grasshoppers congregate, typically due to drought or food scarcity, it triggers a spike in serotonin levels and the insects experience a phenotypic shift: from a solitary lifestyle to a gregarious (social) one.
On top of everything else, 2020 is seeing record highs in terms of locust swarms. Yet nothing quite compares to the infamous Albert’s swarm of 1875. The swarm was named for Albert Child, a physician and amateur meteorologist credited with estimating the size of the swarm of Rocky Mountain locusts at 198,000 square miles. Using his calculations, the number of individual locusts during the swarm of 1875 is placed somewhere between 3.5 trillion and 12.5 trillion.
The Rocky Mountain locust is now extinct, and its eradication came swiftly after it plagued the American midwest through much of the mid- to late 1800’s. As farming and agricultural practices expanded westward towards the Great Plains, Melanoplus spretus not only consumed the crops, but leather horse harnesses, wool straight from the sheep’s back, wood, clothes; you name it. As the farmers of the time put it, they “ate everything but the mortgage.”
Efforts to control the swarms ranged from burning them to eating them, and in 1877, farmers had finally had enough. Locust bounties by the bushelful were commonplace, with Nebraska even instituting the “Grasshopper Act,” stating that every able-bodied person between the ages of 16 and 60 was required to devote two full days to destroying locust nymphs during the spring hatch or face a $10 fine.
In addition to bounties, farmers began raising hardier winter wheat crops, which could be harvested before the locusts matured; this phenological shift is considered a major factor in the species extinction.
Ultimately, the extinction of the Rocky Mountain locust remains somewhat of a mystery: during swarms, the locusts would reproduce on the prairies, and as easily accessible food became more abundant, they would swarm further eastward, with each generation becoming smaller and smaller. But remember, locusts are inherently solitary insects, like other grasshopper families, and it is thought that the species’ permanent breeding ground was a small swath of fertile soil occurring near Rocky Mountain streams and creeks. That land was ultimately exploited by settlers, with some reports suggesting “that farmers killed over 150 egg cases per square inch while plowing, harrowing or flooding.”
What was once considered a vast and innumerable pest of the plains suddenly vanished within a few decades, and it happened so quickly that scientists and collectors barely had the foresight to collect any specimens, so very few exist today.
However, Montana may hold the key to unlocking the mysterious life history of the Rocky Mountain locust, so tune in next week for part 2 as we explore Grasshopper Glacier!