What caused the massive Locust Plague of 1874?

During the summer of 1874, a massive swarm of Rocky Mountain locusts swept across the Great Plains of the United States and Canada, causing hundreds of millions of dollars in agricultural damage. Residents reported swarms so dense that they blocked out the sun for up to six hours. This event is remembered as the last great swarm of the species, which is theorized to have subsequently gone extinct, while locust plagues in general have historically devastated crops and caused famines.

What we know

• The Locust Plague of 1874 involved a large swarm of Rocky Mountain locusts spreading over the Great Plains in the United States and Canada during the summer of 1874. [2]
• The locust swarms caused hundreds of millions of dollars in damage across an estimated area of 2 million square miles. [2]
• Local residents described swarms so thick that they covered the sun for up to six hours. [2]
• Locust swarms have historically devastated crops and have caused famines and human migrations, being mentioned in ancient texts and scriptures. [4]

Still open

• The exact reasons and mechanisms behind the complete extinction of the Rocky Mountain locust after its last great swarm remain theorized rather than definitively proven.

Where to go next

• how it workedWhy do normally solitary grasshoppers suddenly form destructive swarms?
• how we knowHow did ancient civilizations record historical locust plagues?
• a case in pointWhat makes the Australian plague locust a major agricultural pest today?
• what followedHow do modern agricultural practices and insecticides control locust populations?
• the bigger pictureWhat are the broader biological characteristics of short-horned grasshoppers?
• an unexpected connectionHow can large insects eaten as human delicacies also devastate continental agriculture?While locust swarms are infamous for destroying crops and causing widespread famines, the insects themselves are large enough to be harvested and eaten as human food across various cultures.

Sources

• [1]Locust Plague of 1874 (Wikidata Q115380187) · CC0 1.0
• [2]Locust Plague of 1874 · CC BY-SA 4.0
• [3]Australian plague locust · CC BY-SA 4.0
• [4]Locust · CC BY-SA 4.0
• [5]Plagues of Egypt · CC BY-SA 4.0