Invertebrates
Mormon Cricket
Anabrus simplex · also called shield-backed katydid
Every few years, parts of the American West are crossed by a slow-moving tide of large dark insects, millions strong, climbing over fences, cars, and each other. They are called Mormon crickets, they are not crickets, and much of what drives them forward is the fact that the ones behind will eat the ones that stop.
Overview
Anabrus simplex is a flightless shield-backed katydid of the sagebrush country of the western United States. It is a wide-ranging omnivore, eating hundreds of plant species plus seeds and animal matter, including other Mormon crickets.
The name
It comes from 1848, when swarms devoured the crops of Mormon pioneers near Salt Lake City and flocks of gulls arrived to eat the insects — the miracle of the gulls. The California gull is now Utah’s state bird.
Marching bands
In outbreak years the insects form dense bands kilometres long, moving one direction at up to 2 km a day. An individual that stops walking is quickly cannibalised by those behind, seeking protein and salt, which keeps the whole band flowing. Like locusts, the species has a harmless solitary green form and a restless, dark, gregarious swarm form.
Status
Least Concern — native, widespread, and secure, cycling through years of scarcity and outbreak. Big outbreaks are managed as an agricultural pest.
Mormon Cricket: common questions
Is a Mormon cricket a cricket?
No. It is a katydid, specifically a shield-backed katydid in the family Tettigoniidae, and it is only distantly related to true crickets. Early European-American settlers in the Great Basin called any large, dark, ground-dwelling insect that ate their crops a cricket, and the name stuck to this species because of its role in the 1848 plague near Salt Lake City. The giveaways that it is a katydid include the very long thread-like antennae, longer than the body, the large smooth shield over the thorax, and the female's long sword-shaped ovipositor. True crickets have shorter antennae and a different body shape.
What is the miracle of the gulls?
In the spring of 1848, the first substantial crops planted by Mormon pioneers in the Salt Lake Valley were attacked by swarms of Mormon crickets moving down from the foothills. According to accounts passed down in the community, large flocks of California gulls then appeared, fed on the insects for days, and saved enough of the harvest to see the settlers through. Latter-day Saints remember this as a providential deliverance, the miracle of the gulls, and it is commemorated by the Seagull Monument in Salt Lake City and by the choice of the California gull as Utah's state bird. Gulls do genuinely eat Mormon crickets in large numbers, along with many other birds.
Why do Mormon crickets march in huge bands?
The marching is a response to crowding and to a shortage of two things the insects crave, protein and salt. When Mormon crickets reach high density they shift into a restless, gregarious phase and begin moving together across the landscape. Each insect is partly trying to reach fresh food and partly trying to avoid being eaten, because a Mormon cricket that stops moving is rapidly cannibalised by the hungry crickets behind it. The result is a self-propelled band that flows in one direction, sometimes for weeks, and can strip rangeland and gardens, block roads, and pile up against buildings.
Do Mormon crickets bite or harm people?
They are not dangerous. A large Mormon cricket can deliver a weak nip with its jaws if handled, and the female's long ovipositor looks alarming but cannot sting. The insects do not carry disease and do not seek out people. The problems they cause are agricultural and practical. They consume rangeland forage and crops during outbreaks, their crushed bodies make highways dangerously slippery, and the smell and mess of millions of insects moving through a town are considerable. Control during major outbreaks relies on baits and barriers around fields and homes.