Most contacts between adult male field crickets involve aggressive behavior by one or both individuals and terminate with the obvious retreat of one individual. Aggressive behavior consists of one or more of several actions: in mild encounters there is either rearing of the forebody, lashing of the antennae, and shaking of the body, or else rearing of the hind body, kicking with the hind legs, and shaking of the body; in intense encounters, antennal lashing and rearing of the forebody are followed by spreading the mandibles, stridulating distinctively, rushing forward, sparring with the forelegs, butting with the head, and grappling, wrestling, or biting with the mandibles. A male is often flipped back or thrown sideways, but mutilation as a result of fighting is rare, and only in the most intense encounters is the winner determined by what seems to be superior strength or fighting ability. The outcomes of most encounters are determined by the relative tenacity of the two males, and the intensity of aggression exhibited is correlated with the length of the fight, continued aggressive activity developing into increasingly severe combat until one male finally retreats. Groups of adult male field crickets caged in small arenas form essentially linear dominance hierarchies which are stable for short periods of time and which can be described in terms of several characteristics: (1) each male dominates all or nearly all of his encounters with males below him in the hierarchy, (2) the total number of encounters by individual males decreases gradually toward the bottom of the hierarchy, (3) the intensity of aggression exhibited during encounters decreases more or less gradually toward the bottom of the hierarchy and the numbers of no-decision and no-aggression encounters and actively homosexual contacts increase, and (4) encounters between males which rank next to each other are usually more intense than encounters between males which are far apart in the hierarchy.