A Taxonomy Resource

Interactive Guide to Bees of the Prairie Pollinator Project


Interactive Guide to Bees of the Prairie Pollinator Project is the result of a labor of love which emerged from the Prairie Pollinator Project and related efforts to understand and identify pollinators in the Pacific Northwest.

We are not taxonomists, but we have learned to identify most of the taxa among our collection of 10,000 insects as a part of the Prairie Pollinator Project. How is this possible? Identification keys are the basic tools. The standard form of taxonomic key is dichotomous, or “branching”, and requires a series of characteristics of the pollinator be identified in a specific order. Each dichotomy narrows down the set of criteria for diagnosing the species. At the end of the process, you have a hypothesis: Species X! Unfortunately—if you are not a practiced specialist—these keys can be difficult to find and prohibitively complex. Your success might depend on a clear understanding of fancy terms like rugulose, and coriarius. You might need to compare your specimens to reference material in a collection that you do not have access to. Alternatives for the non-specialist have been needed.

To address this challenge, pollinator enthusiasts at IAE have worked to produce interactive (or matrix) keys. These are structured so that a user chooses character traits in any order, narrowing the list of likely matches at each step. If the user of a genus key can identify their specimen as about 5 mm and metallic green, they will have cut their list of likely targets from 23 to 4. If the next choice is more difficult, e.g. “Is the basal vein arched?”, the interactive key provides clear photos that clarify the meaning of the question for the non-specialist.

User-friendly, interactive keys are tools needed by the majority of people working to identify bees in the field and in their own backyard. These include land managers, ecologists, and wildlife enthusiasts across the Pacific Northwest.

We have developed interactive keys that allow us to track identifications for our own specimens, collected in Willamette Valley and western Washington. We offer them here, noting the following limitations:

  • These keys are far from comprehensive. We only attempt to describe species within our own collection, which are associated with prairie habitats in the Willamette Valley and Cascadian area of Washington. Males are poorly represented in these keys.
  • They are intended to begin assessing the diversity represented in a collection. They are not substitutes for a more detailed (and more difficult) scientific analysis. A definitive answer requires genuine expertise in most cases. Any identifications made with these keys should be considered a hypothesis, pending further expert advice.
  • They include taxa referred to as morphospecies—cases where we don’t know the species identification, but we know that it is distinct from other species in the key.
  • They are always in draft form. We regularly revise our categories, correct errors, and welcome feedback. Send us your ideas for how we can improve our pollinator guides! Contact David Cappaert at [email protected] for more information.
Lasioglossum titusi. One of the most common Willamette Valley sweat bees.

How to Identify Bees in the Willamette Valley and Beyond

If you have a city garden with wildflowers, or if you visit local prairie sites (like Herbert Farm in Corvallis), you will have the opportunity to see a dozen (or more) bee species. If you look closely, you will be impressed by the variations on the theme of “bee.” In a few hours, you are guaranteed to observe:

  • Bumblebees of several species.
  • Ceratina, tiny, shiny green bees.
  • Sweat bees (Halictidae), of which most species are dark and striped, but which also includes the brilliant green of Agapostemon.
  • Mason bees, leafcutters, long-horns, nomad, …

Many of the photos of bees shown here were taken at Herbert Farm. How would you learn their names? The easiest route would be to upload the images to the citizen science site iNaturalist, which would match these to Bombus vosnesenskii, Agapostemon sp, and Ceratina sp. All told, iNaturalist records 23,000 records for 170 bee species in Oregon. Most of the time, iNaturalist will match a field photo at family, and often to genus.

If you were more intent on learning bees (particularly if you also have a microscope), you could use the recently published (Dec 2023) Bees of the Pacific Northwest: Key to Genera. This resource covers the 60 (!) genera of the broader Pacific Northwest. Another useful reference, also new in 2023: Common Bees of Western North America, which goes beyond ID to describe the natural history of these species. If you are interested in acquiring genuine expertise, the Oregon Bee Atlas runs a yearly Master Melittologist Apprentice Program, an “introductory self-paced course of study, with opportunities for working with mentors in the field.”

Lasioglossum sp., sweat bee, on Gilia capitata.

How IAE Identifies Bees

We have a collection that runs into the tens of thousands of specimens, part of the Prairie Pollinator Project, a collaborative effort of Quamash EcoResearch and the Institute for Applied Ecology. In Oregon, we have sampled pollinators of an endangered plant, Willamette daisy (Erigeron decumbens). In both Oregon and Washington, we developed pollinator networks for every plant in bloom in more than a dozen prairie sites between 2017 and 2023. Our latest technical report on this project was published March 1, 2023 and is available on our website here.

First step, Genus: We have seen 20-odd genera in our sites, which are fairly easy to distinguish. We have documented these in our own interactive key, Bee Genera of the Prairie Pollinator Project.

The harder step, species: We have determined species names for most of our bees, which involved combing through often difficult technical keys, learning the obscure terminology, and asking the experts. Sometimes, we create our own resources, because the existing literature is incomplete—especially for western bees. A couple of examples:

The mining bee genus, Andrena, is the most speciose bee genus in the world; in Oregon, there are 140 possible species. Consulting the academic literature on Andrena, we encountered two problems. One, the specialized terminology is poorly documented and difficult to interpret. So we created Andrena deconstructed: guide to the characters of the DiscoverLife key, with detailed images explaining the meaning of bidentate labral process and trochanteral flocculus. A second problem with Andrena is that the most useful resources first require a diagnosis of the subgenus. So we consulted the literature and wrote the Key to the Andrena subgenera (females) of the Pacific Northwest.

We have also spent serious time on the sweat bee genus Lasioglossum. In this case, there is no comprehensive key for our PNW species, period. So we built the Weak-veined Lasioglossum of the Prairie Pollinator Project. The key includes species described elsewhere, and several morphospecies—taxa that we could not assign to species, but wanted to document until new information becomes available. At least a couple of these were identified by an expert that reviewed our key—and one that is potentially a new species.

Why do we make such an effort to ID to the species level? Because every kind of bee contributes to pollination in a unique way. We have seen a dozen Lasioglossum species; only one has distinctive hooked hairs adapted for foraging on evening primrose. Of the many Andrena we have collected, only one forages on the toxic death camas. Many other such examples of unique relationships exist, most as yet unknown. In the meantime, we record everthing.