Figure 1.

Pictogram illustrating the stereotyped sequence of escalating motor performances characteristic for aggressive encounters between male crickets. Level 0, Mutual avoidance: no aggressive interaction. Level 1, Preestablished dominance: one cricket attacks, the other retreats. Level 2, Antennal fencing. Level 3, Mandible spreading (unilateral): one cricket displays spread mandibles. Level 4, Mandible spreading (bilateral): both crickets display spread mandibles. Level 5, Mandible engagement: the mandibles interlock, and the animals push against each other. Level 6, Grappling: an all-out fight; the animals may disengage and reengage to bite other body parts. Establishment: the fight can be concluded at any level by one opponent retreating (the loser, or subordinate). This establishes the winner (dominant), which then typically produces the rival song and body-jerking movements [modified from Stevenson et al., (2000)].