Crickets are big chirping omnivores or herbivores, depending on the species. They are part of the family Gryllidae. The Gryllidae are mostly cylindrical bodies, round heads, and long antennae. Behind the head is a smooth, strong prothorax. A prothorax is the middle area between the head and the abdomen, the body. If we had a prothorax, that would be our neck. The abdomen ends in a pair of long cerci (spikes). The females have a long, cylindrical tube used to deposit eggs. The hind legs have enlarged thighs, giving power for high jumps. The front wings are adapted as tough, leathery elytra (wing covers). Some crickets chirp by rubbing parts of these elytra together. The hind wings are membrane-like and are folded when not in use for flight. Many species, however, cannot fly. The largest members of the family are the bull crickets, which are up to 5 cm (2 in) long.
The Gryllidae are found all around the world except at latitudes of 55° or higher, with the greatest diversity being in the tropics. They occur in varied habitats from grassland, bushes, and forests to marshes, beaches to caves.
Crickets are mainly nocturnal, and are best known for the loud, persistent, chirping song of males trying to attract females, although some species produce no noise. The singing species have good hearing, via the eardrums on the inner bones of the front legs.
Captive crickets are omnivorous; when deprived of their natural diet, they accept a wide range of organic foods. Some species are completely herbivorous, feeding on flowers, fruit, and leaves, with species that live on the ground consuming seedlings, grasses, pieces of leaf, and the shoots of young plants. Others are more predatory and include in their diet invertebrate eggs, larvae, pupae, molting insects, scale insects, and aphids. Many are scavengers and consume various organic remains, decaying plants, seedlings, and fungi. In captivity, many species have been successfully reared on a diet of ground, commercial dry dog food, supplemented with lettuce and aphids.
Male crickets establish their dominance over each other by aggression. They start by lashing each other with their antennae and flaring their mandibles. Unless one retreats at this stage, they resort to grappling, at the same time each emitting calls that are quite unlike those uttered in other circumstances. When one achieves dominance, it sings loudly, while the losers remain silent.
Crickets have many natural enemies and are subject to various pathogens and parasites. They are eaten by large numbers of vertebrate and invertebrate predators and their hard parts are often found during the examination of animal intestines. House geckos have learned that although a calling decorated cricket may be safely positioned in an out-of-reach burrow, female crickets attracted to the call can sometimes be intercepted and eaten.
The entomopathogenic fungus attacks and kills crickets and has been used as the basis of control in pest populations. The insects are also affected by the cricket paralysis virus, which has caused high levels of fatalities in cricket-rearing facilities. Other fatal diseases that have been identified in mass-rearing establishments include Rickettsia and three further viruses. The diseases may spread more rapidly if the crickets become cannibalistic and eat the corpses.
Red parasitic mites sometimes attach themselves to the dorsal region of crickets and may greatly affect them. The horsehair worm is an internal parasite and can control the behavior of its cricket host and cause it to enter water, where the parasite continues its life-cycle and the cricket likely drowns. The larvae of the sarcophagid fly develop inside the body cavity of field crickets. Female parasitic wasps of Rhopalosoma lay their eggs on crickets, and their developing larvae gradually devour their hosts. Other wasps in the family Scelionidae are egg parasitoids, seeking out batches of eggs laid by crickets in plant tissues in which to insert their eggs.
The fly Ormia ochracea has very acute hearing and targets calling male crickets. It locates its prey by ear and then lays its eggs nearby. The developing larvae burrow inside any crickets with which they come in contact and in the course of a week or so, devour what remains of the host before pupating. In Florida, the parasitic flies were only present in the autumn, and at that time of year, the males sang less but for longer periods. A trade-off exists for the male between attracting females and being parasitized.