Evaluation of nest-site selection of ground-nesting bees and wasps (Hymenoptera) using emergence traps

Approximately 70% of the 30 000 known bee (Hymenoptera) species and most flower-visiting, solitary wasps (Hymenoptera) nest in the ground. However, nesting behaviours of most ground-nesting bees and wasps are poorly understood. Habitat loss, including nesting habitat, threatens populations of ground-nesting bees and wasps. Most ground-nesting bee and wasp studies implement trapping methods that capture foraging individuals, but provide little insight into the nesting preferences of these taxa. Some researchers have suggested that emergence traps may provide a suitable means by which to determine ground-nesting bee and wasp abundance. We sought to evaluate nest-site selection of ground-nesting bees and wasps using emergence traps in two study systems: (1) planted wildflower enhancement plots and fallow control plots in agricultural land; and (2) upland pine and hammock habitat in forests. Over the course of three years (2015-2017), we collected 306 ground-nesting bees and wasps across all study sites from emergence traps. In one study, we compared captures per trap between coloured pan traps and emergence traps and found that coloured pan traps captured far more ground-nesting bees and wasps than did emergence traps. Based on our emergence trap data, our results also suggest ground-nesting bees and wasps are more apt to nest within wildflower enhancement plots than in fallow control plots, and in upland pine habitats than in hammock forests. In conclusion, emergence traps have potential to be a unique tool to gain understanding of ground-nesting bee and wasp habitat requirements.