Off the field in televised matches, there is usually a third umpire who can make decisions on certain incidents with the aid of video evidence. The third umpire is mandatory under the playing conditions for Test and Limited Overs International matches played between two ICC full member countries. These matches also have a match referee whose job is to ensure that play is within the Laws and the spirit of the game.
Most bowlers are considered specialists in that they are selected for the team because of their skill as a bowler, although some are all-rounders and even specialist batsmen bowl occasionally. The specialists bowl several times during an innings but may not bowl two overs consecutively. If the captain wants a bowler to "change ends", another bowler must temporarily fill in so that the change is not immediate.
Cricket is one of many games in the "club ball" sphere that basically involve hitting a ball with a hand-held implement; others include baseball, golf, hockey, tennis, squash, badminton and table tennis. In cricket's case, a key difference is the existence of a solid target structure, the wicket (originally, it is thought, a "wicket gate" through which sheep were herded), that the batsman must defend. The cricket historian Harry Altham identified three "groups" of "club ball" games: the "hockey group", in which the ball is driven to and fro between two targets (the goals); the "golf group", in which the ball is driven towards an undefended target (the hole); and the "cricket group", in which "the ball is aimed at a mark (the wicket) and driven away from it".
There are various formats ranging from Twenty20, played over a few hours with each team batting for a single innings of 20 overs, to Test matches, played over five days with unlimited overs and the teams each batting for two innings of unlimited length. Traditionally cricketers play in all-white kit, but in limited overs cricket they wear club or team colours. In addition to the basic kit, some players wear protective gear to prevent injury caused by the ball, which is a hard, solid spheroid made of compressed leather with a slightly raised sewn seam enclosing a cork core which is layered with tightly wound string.
Captive crickets are omnivorous; when deprived of their natural diet, they accept a wide range of organic foodstuffs. Some species are completely herbivorous, feeding on flowers, fruit, and leaves, with ground-based species 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, moulting 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.