PLoS ONE doi:10.1371/journal.pone.0003980 (2008)

Large body size confers obvious advantages in cricket fights, but Chinese gamblers have also looked to the head when placing their bets going back some eight centuries. New research bolsters the practice, providing the first evidence that males have developed larger heads — and mouth parts — as weaponry in aggressive turf battles.

Kevin Judge and Vanessa Bonanno at the University of Toronto Mississauga in Canada pitted fall field crickets (Gryllus pennsylvanicus) of similar body size against each other; those with bigger heads and mouth parts won 75% of battles that escalated to 'grappling'. The bigger the difference in head size, the more likely the head-strong cricket was to win.

But the team found no evidence of signalling that would influence disputes settled before grappling took place, suggesting that evolutionary selection takes place in the heat of the battle.