By Arthur V. Evans
My first encounter with one of these giant, almost ant-like creatures occurred when I was about seven or eight years old and living on the fringes of the Mojave Desert in southern California. The inch-long insect had thread like antennae attached to an oversized head, a wingless narrow midsection armed with thick spiny legs and a fat abdomen distinctly banded in black and tan. I approached the animal cautiously, but closer inspection revealed that the insect was dead, frozen forever in a sprawling, lifelike pose. I carefully picked up the stiff corpse and presented it to my dad, who told me it was a Jerusalem cricket.
Resembling a cross between Jiminy Cricket and a Cootie, Jerusalem crickets – or JCs as they are fondly known by some – are impressive animals. Their large, round and naked heads are fitted with two small black eyes suggesting the head of a child. Jerusalem crickets are often the subject of fear and superstition and have been given a variety of monikers.
They have been dubbed Child of the Earth or Niña del la Tierra in Spanish. The Navajo thought them deadly poisonous and called them “wó se ts´inii,’ or the “skull insect” or “bone neck beetle.” Their powerful jaws are used for digging and chewing roots. Jerusalem crickets can bite with considerable force if handled, but are not poisonous in any way. In California, JCs are known as potato bugs due to their predilection for nibbling on potatoes and other crops in direct contact with the soil. Extensive damage to crops and gardens by these insects is rare. They also occasionally scavenge dead animal matter and may engage in cannibalism. The name “Jerusalem cricket” is believed to have originated in the 19th century when ‘Jerusalem’ was a commonly used as an expletive. It is easy to imagine that unexpected encounters with these crickets could easily illicit such outbursts until the name eventually stuck!
Jerusalem crickets, including the genera: Ammopelmatus, Stenopelmatus and Viscainopelmatus, belong the family Stenopelmatidae and are related to crickets and katydids. They resemble the large king crickets of South Africa and the giant wetas of New Zealand, both of which are now classified in the family Anostotsmatidae.
Jerusalem crickets are distributed throughout much of western North and Central America, where they live in almost every imaginable habitat from coastal and desert sand dunes to montane and tropical forests. Of the more than 100 species of JCs known, only about a third been formally described in the scientific literature. Most of the 60-80 species living in the western United States call California home.
The Kelso Jerusalem Cricket (Ammopelmatus kelsoensis), Point Conception Jerusalem Cricket (Ammopelmatus muwu) and Coachella Valley Jerusalem Cricket (Stenopelmatus cahuilaensis) are all restricted to coastal or desert dunes. These sandy habitats are under assault from developers, off-road vehicle use, and agricultural interests. The localized distribution and sensitivity to habitat disruption of these and other JCs require further study and may result federal or state protection.
Adult males are distinguished by a pair of small black hooks located between the cerci, a pair of short projections near the tip of the abdomen. Adult females have the short blades of their egg-laying tube or ovipositor located just beneath the cerci.
Sexually receptive males and virgin females drum their abdomens on the soil to attract species of their own kind. The drumming is audible nearly 60 feet away and is “heard” by special organs located near the bottom of each leg of the JC.
Courtship involves a bit of a tussle and sometimes resembles an energetic wrestling match as the male grapples for position. Eventually the male deposits a sperm packet, after which the female may kill and eat her mate. The function of the sperm packet in JCs is not understood. In other crickets and katydids the packet not only provides the female with reproductive materials and a nutritious snack, it also serves to block the amorous advances of other males.
Eggs are probably laid in small clutches in the soil soon after mating. They are oval and white with a roughened surface. In California, JCs reach adulthood during the summer. Small nymphs appear either by fall or early the following spring. Hatchlings resemble miniature adults and may take nearly two years to develop, while individuals experiencing nutritional deficiencies or parasitic infections may take up to five years. Nymphs may molt up to eleven times before reaching maturity. Like stick insects, JCs can regenerate legs lost during molting. In time, the new leg may approximate a normal leg in size, increasing in size with each successive molt.
Plump and juicy, JCs are an excellent potential food source for many animals. Bats, coyotes, foxes and owls prey them upon. It is not uncommon to find their droppings and pellets studded with the tough and distinctive remains of JCs mixed with the bones and fur of other animals.
Tachinid flies and horsehair worms attack and parasitize Jerusalem crickets. Dead JCs found in or near pools and streams are often infested with horsehair worms that must emerge from the body of the host and complete their life cycle in the water.
When threatened, JCs may suddenly kick out to brandish their thick spiny hind legs, menacingly raising them up over their body. Others will somersault on their backs, flailing their spiny legs forcefully in the air. Their mandibles are opened wide, capable of delivering a painful nip. Some species produce a scraping sound when agitated by scraping their legs against rough plates on the side of the abdomen. A few Mexican and Central American species are even capable of jumping when disturbed.
Jerusalem crickets are usually found under objects on the ground during the cooler, wetter months of the year. Trails of oatmeal left along paths will attract foraging crickets that will follow the food-laden path as they feed. Pitfall traps (cans or jars sunk in the ground so the opening is flush with the surface) baited with oatmeal will also attract hungry JCs.
Jerusalem crickets do well in captivity. Because of their cannibalistic tendencies they must kept in separate containers. Fill an eight-ounce margarine tub with damp, sterilized, fine-grained sand and cover with a lid punched with a few small holes. The containers must be kept cool since temperatures exceeding 70 ºF may not only be harmful to JCs, but also encourages the development of mites. Humidity is critical. The substrate must be kept moist, but not wet, at all times.
Fresh slices of apple or potato offered every 7-10 days will not only provide your animals with nutrition, but also help maintain humidity. Add washed romaine lettuce and “old-fashioned” oatmeal. Jerusalem crickets will also eat bread, grass roots and a variety of vegetables. Supplement their weekly feedings with bits of raw meat or soft-bodied insects such as greater wax moth larvae (Galleria melonella). Remove uneaten food items after a few days to prevent the growth of potentially harmful molds.
Both immature and adult JCs have been kept successfully in captivity, but reports on egg-laying have never been published. In the wild, eggs are probably laid well below the surface so they are not subjected to freezing temperatures.
Nymphs molt on their backs with the old exoskeleton positioned behind them. After molting is complete, the JC will right itself and eat the caste, recycling vital minerals needed for the development of the new exoskeleton.
Throughout the western United States JCs are familiar, yet exotic, insects. In spite of their secretive nature, they still make unusual and interesting pets, even if kept only for a short period. Much remains to be learned about these incredible animals. Carefully recorded observations of your captive JCs may help to reveal their mysterious lives.
Field, L.H. (editor). 2001. The biology of wetas, king crickets, and their allies. CABI Publishing. Wellingford, UK.
Poinar, G. and D.B. Weissman. 2004. Horsehair worms and nematode infections of North America Jerusalem crickets, field crickets, and katydids (Orthoptera: Stenopelmatidae, Gryllidae, and Tettigoniidae). Journal of Orthoptera Research 13(1): 143-147.
Weissman, D. 2005. Jerusalem? Cricket! (Orthoptera: Stenopelmatidae: Stenopelmatus); origins of a common name. American Entomologist 51(3): 138-139)
Weissman, D. The dark side of entomology. http://www.calacademy.org/science_now/archive/where_in_the_world/jerusalem_crickets.php (accessed 16 March 2011)
© 2010, A.V. Evans