Can cavity-nesting bees and wasps be reliably identified from participatory science observations of nest characteristics?

As with other insects, solitary cavity-nesting bees and wasps (Hymenoptera: Aculeata) are facing decreases in species diversity due to anthropogenic change. Participatory science may be a promising way to monitor bee and wasp biodiversity, especially within suburban habitats. The Bees’ Needs was one such participatory science project, run by the University of Colorado Museum of Natural History from 2013 to 2016. The Bees’ Needs distributed over 1,000 nesting blocks across the Front Range Urban Corridor of Colorado and collected data on over 13,000 bee and wasp nests. This study determined which species of cavity-nesting bees and wasps used The Bees’ Needs nesting blocks and identified the nest characteristics important for taxonomic identification of bees and wasps based on their nests. For each taxon of bee and wasp observed in The Bees’ Needs, I summarized the compositions of their nest plugs, dates of nest completion, diameters of nesting holes inhabited, and their elevational distributions. I then leveraged these nest characteristics to develop a predictive classification model to identify which taxon of bee or wasp made each nest based on the nest’s characteristics. The final key resulting from this classification model was able to correctly classify 90.2% of the tested nests and only required four variables to do so: nest plug composition, date of nest completion, tunnel diameter, and elevation. This study demonstrates the usefulness of participatory science initiatives and nesting blocks in bee and wasp biodiversity research and proposes new tools for bee and wasp identification.