Sexual selection has historically been assumed to be a constant and consistent force, driving the evolution of elaborate traits such as animal weapons. However, organisms in the wild exist in heterogeneous and fluctuating resource environments and so the strength of selection on these traits is likely enmeshed in their ecological context. One such species is the leaf footed cactus bug (Narnia femorata), in which males use enlarged hind leg weapons to defend access to ephemeral cactus fruit food resources and secure mating opportunities. To test the effects of resource variation on sexual selection in this species, we tracked the mating interactions and locations of groups of eight individually marked males and females in replicated semi-natural enclosures, constituting either resource-rich (containing 6 cactus fruits) or resource-poor (a single fruit) environments. We found that, over a 5-day period, N. femorata gravitated towards cactus fruit, generating marked differences in the spatial clustering of individuals and mating events across the two resource treatments. Despite this, male and female mating success and female reproductive output across the two resource levels remained surprisingly similar. Continuing to explore the role of environmental resource variation is crucial to understanding sexual selection and mating system dynamics, both in this species and more widely.