The presence of suitable habitat is an important property affecting community structure of all taxa. If nest-sites are limiting, how will this affect community membership? Ants make a great study organism because nest-sites are usually limiting to territorial or substrate-specific nesting species. I hypothesized that the density and spatial arrangement of available nest-sites would affect community structure. In the summer of 2006, 40- 5m2 experimental plots were placed at 4 locations across the foothills ecotone in Boulder and Jefferson Counties of Colorado. All sites were characteristic high elevation grasslands and open meadows. Artificial nest-sites are 18x18cm flagstone tiles of varying thickness (3-6cm) placed flush with the ground after vegetation was removed. The experimental plots were each paired with control and removal sites. Plots were monitored using pitfall trap sampling and visual surveys both before and after the treatment was imposed. There were four groups in the treatment category; control, removal, tile and tile with rock. The density levels were high, low and intermediate. Species richness varies between treatments and density of tiles. There was no effect due to the spatial arrangement of the tiles (aggregated, segregated or random arrangements). My hypothesis that there would be a seasonal effect on species richness was supported. I argue that although traditional studies of community structure have focused on interspecific interactions as the driving mechanism, abiotic factors such as temperature, humidity and space may be equally important in determining community membership.