In species with a resource-defence (male dominance) mating system, males are expected to maximize fitness by controlling resources deemed more valuable by sexually receptive females because these sites attract more mates. Furthermore, males, which control more valuable resources should themselves be of high quality. I experimentally tested these predictions in the laboratory using the sexually dimorphic Wellington tree weta, Hemideina crassidens (Blanchard) (Orthoptera: Tettigonioidea: Anostostomatidae). Male H. crassidens use their mandibular weaponry to fight for control of harems (groups of adult females) that seek shelter in trees cavities (galleries). As predicted, larger galleries housed significantly larger groups of females and males with larger weaponry controlled large galleries significantly more often. Therefore, galleries with a larger volume are likely considered more valuable by males because they house larger harems. However, contrary to prediction, males with larger weaponry did not reside with significantly more females overall because females did not always form the largest possible groups in galleries and males with smaller weaponry were able to reside with single females in small galleries. The latter observation suggests a possible alternative mating strategy by disadvantaged males.