Mormon crickets are large, flightless insects that gather in massive numbers, undertaking extensive migrations. While they do not pose a direct physical danger to people or pets, their sheer numbers during outbreaks can result in considerable damage and disruption. Understanding their behavior and biology helps clarify associated risks.
What Are Mormon Crickets?
Mormon crickets (Anabrus simplex) are a type of shield-backed katydid, not true crickets. These robust, flightless insects move by walking and hopping, despite having small, undeveloped wings. Adult females typically reach 2 to 3 inches (5 to 7.5 centimeters) in length, with males being slightly smaller. Their bodies vary in color from brown, black, red, purple, or green, often with striped patterns, and they possess long antennae.
They are native to arid and semi-arid regions of western North America, thriving in grasslands and sagebrush habitats. Their life cycle begins with eggs laid in the soil during late summer or early fall, hatching the following spring when soil temperatures reach about 40°F (4°C). Nymphs undergo several molts before reaching adulthood, a process that typically takes 60 to 90 days. There is generally one generation per year, though at high elevations, development may take two years.
Mormon crickets form dense marching bands of millions during outbreaks. These bands can travel up to 1.25 miles (2 kilometers) per day and cover 25 to 50 miles (40 to 80 kilometers) in a season, moving primarily during daylight hours. Their diet is omnivorous, primarily consisting of grasses, forbs, and other vegetation. They are also opportunistic feeders, consuming dead insects, carrion, and engaging in cannibalism when food is scarce or populations are dense, often driven by a need for protein and salt.
Assessing the Threat
Mormon crickets are not directly dangerous to humans or pets. They are not venomous, do not transmit diseases, and are not poisonous. While they possess strong mandibles, they rarely bite humans. Any bite is generally mild, causing only minor irritation similar to a mosquito bite, and typically occurs only if the insect feels threatened or is handled.
The primary threat from Mormon crickets stems from their voracious appetites and overwhelming numbers during outbreaks. Swarms can cause significant damage to agriculture, devouring crops such as wheat, barley, alfalfa, and various vegetables. They also impact rangelands by consuming grasses and forbs, which reduces forage for livestock and wildlife. Historically, outbreaks have led to substantial economic losses for farmers and ranchers.
Beyond agricultural damage, large aggregations of Mormon crickets can create hazardous conditions and nuisances. When millions cross roads, their crushed bodies can make pavement slick, posing a safety hazard for drivers. The sheer volume of insects can also be overwhelming, congregating on buildings and entering homes, creating an unpleasant odor as they die and decompose. Environmentally, their feeding habits can disrupt plant communities, contribute to soil erosion, and affect water quality, especially in drought-stricken areas.
Managing Their Presence
Managing Mormon cricket populations, particularly during outbreaks, often involves multiple strategies. One preventative measure includes targeting their eggs; tilling soil in the fall can expose eggs to freezing temperatures, effectively reducing their numbers before they hatch. Reducing excess vegetation and debris around properties can also discourage them by eliminating food sources and hiding places.
Physical barriers are an effective control method against these flightless insects. Fences made of slick materials like galvanized iron, plastic sheeting, or chicken wire, at least 20 to 24 inches (50 to 60 centimeters) high, can deter them from entering specific areas. These barriers are often angled or used with trenches or pits to trap the crickets.
Chemical control options include baits containing insecticides like carbaryl, applied directly or indirectly through cannibalism. Insecticides can also be sprayed on crops, though direct spraying may not save the crop due to swarm size. Biological controls leverage natural enemies; birds, rodents, and certain wasps prey on Mormon crickets. Biopesticides based on the fungus Nosema locustae can interfere with their digestive systems, leading to mortality. Coordinated community efforts are often necessary for effective management of large-scale outbreaks.