Sexual selection research has traditionally focused on mate choice over intrasexual competition because the former mechanism was initially controversial and its theoretical foundations were not immediately recognized. This has resulted in the relative underdevelopment of research into the evolution of intrasexual competition and the weapons that one sex uses during aggressive physical combat over the other sex. This is in spite of the fact that the natural world abounds with examples of weaponry, particularly in males. My collaborators and I are studying the relationship between male weaponry and aggressive behaviour in field crickets (Orthoptera, Gryllidae, Gryllinae), a group that has become a model system for the study of male-male competition, but has received little attention from researchers interested in weaponry. Previous work has shown that in Gryllus pennsylvanicus, males with proportionately larger heads and mouthparts win more fights than males with proportionately smaller heads and mouthparts. Our current study tests whether this intraspecific pattern holds across nine species of field cricket found in North America. We raised all nine species under consistent laboratory conditions and then videoed 10-minute interactions between pairs of male crickets of the same species. Videos were scored for the intensity of aggressive behaviours, and each participant was measured for a variety of body dimensions, including weaponry. I will present the results of this research for all nine species mapped onto a recent phylogeny of North American field crickets to test: a) the prediction that morphological diversity in this group is correlated with the prevalence of aggressive combat, and b) whether the influence of weaponry on success in combat is consistent across species.