Compact housing in built-up areas: spatial patterning of nests in aggregations of a ground-nesting bee

1. The spatial patterning of nests in ten aggregations of a ground-nesting bee Halictus rubicundus (Christ) was examined using nearest-neighbour dista nce analysis. 2. Large scale aggregation was demonstrated and attributed to a preference for nesting in limited areas of the most suitable substrate in conjunction with natal site fidelity of nest-founding females. 3. Within patches of high nest density, there was a fine-scale regularity r esulting from competition for sufficient substrate to maintain the structur al integrity of the nest. 4. The appropriateness of four statistical tests is discussed with respect to analysing the spatial arrangement of nests in populations with both aggr egated and regular components.