Rocky Mountain Locust

The Rocky Mountain locust was a swarming short-horned grasshopper native to the grasslands of the western United States and southern Canada. It is best remembered for an 1875 outbreak over Nebraska that may have contained several trillion individuals covering an area larger than California, likely the largest swarm of any single animal species ever documented.

Despite this staggering abundance, the species collapsed within about 25 years and has not been reliably observed since the early 1900s. Entomologists now generally consider it extinct, making it a striking cautionary example of how quickly even an overwhelmingly abundant species can disappear.

• Typical short-horned grasshopper body plan, 2–3.5 cm long
• Yellowish-brown to olive body with darker mottling across the wings
• Hind femora often reddish or yellow with dark banding
• Long, narrow forewings extending past the abdomen in the swarming (migratory) phase
• Chiefly identified today from preserved museum specimens and historical accounts rather than living individuals

Historically ranged from the eastern slopes of the Rocky Mountains across the Great Plains, from the Canadian Prairies south into Texas. Permanent breeding grounds are believed to have been narrow river valleys within the mountains, from which swarms periodically erupted onto the plains during droughts.

In its solitary phase the species behaved like an ordinary grassland grasshopper, feeding on native grasses and forbs without causing notable damage. Under favorable weather conditions, populations could shift into a dense, gregarious swarming phase, forming vast migratory clouds that stripped crops and vegetation across the plains during the mid-to-late 1800s, causing severe agricultural losses for settlers.

Eggs were laid in pods in soil during late summer and fall, overwintering before hatching into wingless nymphs the following spring. Nymphs molted through several instars before reaching winged adulthood, typically completing one generation per year. Under swarm conditions, rapid population growth combined with mass migration allowed outbreaks to spread across huge distances in a single season.