1. Sister taxa that coexist in the same space and time often face competition due to the use of similar resources. However, some closely related species can adopt fine-grained specialisation in resource use to coexist. This study investigated niche overlap between three sympatric spider-hunting wasp species of the genus Trypoxylon (Hymenoptera: Crabronidae) known to nest in three of the habitats found in the study area.2. First, the co-occurrence of these wasp species in the three habitats was estimated, as a proxy for potential competition. Then, the following hypotheses were tested: (i) niche partitioning is seen more often between species that co-occur in a habitat, whereas there is niche overlap between species nesting in distinct habitats (prey specialisation hypothesis); and (ii) wasp species capture prey according to their size (physical constraint hypothesis).3. Two pairs of wasp species were found consistently nesting in the same habitat. Niche partitioning based on prey taxa occurred regardless of the habitat preference. It was also found that differences in the size of wasps reflected distinctions in the size of their prey.4. These findings were consistent over the years, showing that the significance of specialisation in foraging activities and physical constraints during prey capture can play key roles in the coexistence of sympatric species. The distinctions in the foraging strategies of these wasps are discussed, as well as potential mechanisms driving the evolution in prey specialisation, with insights for future studies.

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