Higher bee diversity in the canopy than near the ground in a temperate deciduous forest

Bees were sampled in the canopy (> 15 m) and near the ground (0.5 m) in a bottomland hardwood forest in the southeastern United States. In total, 6653 bees from 5 families and 71 species were captured. Augochlora pura (Say) accounted for over 91% of all bees collected and was over 40 times more abundant, on average, in the canopy than near the ground. Bee abundance, richness and diversity were significantly higher in the canopy than near the ground, even after excluding A. pura from the data set. A. pura was consistently more abundant in the canopy than near the ground throughout the season, but was more so in mid-summer. The remaining bee community exhibited a similar pattern. We suspect that bees frequent the canopy, particularly during times of low flower availability, to acquire non-floral resources such as honeydew and sap.