Adding essential oils to emergence tents has taxon-specific effects on trapping efficiency of ground-nesting bees

Soil emergence tents (e-tents) are a new tool for studying the nesting biology of ground-nesting bees. E-tents allow us to link nests with specific soil conditions; however, low success probabilities (≤ 20% of e-tents capture at least one bee) and long deployment times (> 72 h) limit their efficiency. We examined if adding scents—spearmint and lemongrass essential oils—increases how quickly e-tents capture bees actively nesting in the soil directly covered by the trap (“capture rate”), letting e-tents be moved more frequently to sample more area. Adding essential oils did not have a significant effect on the overall capture rate. However, in e-tents with spearmint essential oil, bees in the family Halictidae were captured 1.80× faster, and there was a trend for reduced capture rate for the family Andrenidae. The efficacy of adding scents to e-tents appears to be taxon-specific. Researchers interested in halictid nesting biology may increase the efficacy of e-tents with spearmint essential oil, but further work is needed to find a suitable attractant for other groups or whole communities.