In the approximate centre of the field is a rectangular pitch (see image, below) on which a wooden target called a wicket is sited at each end; the wickets are placed 22 yards (20 m) apart. The pitch is a flat surface 3 metres (9.8 ft) wide, with very short grass that tends to be worn away as the game progresses (cricket can also be played on artificial surfaces, notably matting). Each wicket is made of three wooden stumps topped by two bails.
Crickets are kept as pets and are considered good luck in some countries; in China, they are sometimes kept in cages or in hollowed-out gourds specially created in novel shapes. The practice was common in Japan for thousands of years; it peaked in the 19th century, though crickets are still sold at pet shops. It is also common to have them as caged pets in some European countries, particularly in the Iberian Peninsula. Cricket fighting is a traditional Chinese pastime that dates back to the Tang dynasty (618–907). Originally an indulgence of emperors, cricket fighting later became popular among commoners. The dominance and fighting ability of males does not depend on strength alone; it has been found that they become more aggressive after certain pre-fight experiences such as isolation, or when defending a refuge. Crickets forced to fly for a short while will afterwards fight for two to three times longer than they otherwise would.
Crickets have a cosmopolitan distribution, being found in all parts of the world with the exception of cold regions at latitudes higher than about 55° North and South. They have colonised many large and small islands, sometimes flying over the sea to reach these locations, or perhaps conveyed on floating timber or by human activity. The greatest diversity occurs in tropical locations, such as in Malaysia, where 88 species were heard chirping from a single location near Kuala Lumpur. A greater number than this could have been present because some species are mute.
Some species of cricket are polyandrous. In Gryllus bimaculatus, the females select and mate with multiple viable sperm donors, preferring novel mates. Female Teleogryllus oceanicus crickets from natural populations similarly mate and store sperm from multiple males. Female crickets exert a postcopulatory fertilization bias in favour of unrelated males to avoid the genetic consequences of inbreeding. Fertilization bias depends on the control of sperm transport to the sperm storage organs. The inhibition of sperm storage by female crickets can act as a form of cryptic female choice to avoid the severe negative effects of inbreeding. Controlled-breeding experiments with the cricket Gryllus firmus demonstrated inbreeding depression, as nymphal weight and early fecundity declined substantially over the generations' this was caused as expected by an increased frequency of homozygous combinations of deleterious recessive alleles.