Our estimated 4,000 native bee species in the United States and Canada fall into one of two categories – pollen generalists and pollen specialists. Generalist bees are the majority, accounting for approximately 75% of all bee species. It is their good fortune to be able to forage on many different native plant species, and often on a number of non-native plants. The European honey bee (nonnative, of course) is also a forage generalist.
Requirements of Specialist Bees
For the other 25% of our native bees, it’s slim pickings for forage sources. Specialist bees rely upon just a handful of native plant species, with some bee species dependent upon a single plant species. Does it matter what you plant in your landscape? It certainly does to a specialist bee!
Specialist bees emerge from their nests when their specific forage plants begin to flower. The relationship is sometimes interdependent – the bee relying upon that particular plant species and the plant depending upon that specific bee species for pollination services. In other cases, the plant may attract many different bee species. While numerous bee species are in trouble, our specialist bees would seem to be at greatest risk.
Here’s a quick exercise – name six native plants in your landscape and the specialist native bees that use them. Can’t do it? Don’t feel too badly, you are not alone. Simply finding a list of the bees that are native to your state can be a challenge, much less a list of forage plants for specialists. Some plants that support specialist bees are less well known in average landscapes, such as Spring Beauty (Claytonia virginica), but other plants are more common, including native Sunflowers (Helianthus spp).
New Research on Specialists
If you live in the Mid-Atlantic or the Northeast, you are in luck – there is a new research report listing many specialist bees and their host plants. “Specialist Bees of the Mid-Atlantic and Northeastern United States” was published by Jarrod Fowler of the Stockbridge School of Agriculture at the University of Massachusetts and Sam Droege of the USGS Patuxent Wildlife Research Center in Beltsville, Maryland.
The authors report on 95 species of specialist bees, with Andrena bees being the most numerous (40 in their study). Andrena bees are a big group – with approximately 1,400 species in North America. They are one of two genera of mining bees, the other being the Perdita genus (most commonly found in the Southwest). Mining bees nest in the soil – a clue to providing proper habitat for them in your landscape – leave patches of bare soil in full sun.
While the authors of the study admit that their research is not exhaustive (native bees have not been well studied, in general) their work is a tremendous resource for those of us who want to plant for pollinators, including helping the supremely challenged bees that are quickly running out of resources due to development and conventional planting practices.
You can make a difference for specialist bees as well as their generalists cousins, by planting the native plants they need. Those specialists just might need a little extra help.
For more information on our native bees, take a look at these helpful resources:
The Xerces Society Guide: Attracting Native Pollinators by the Xerces Society
Bees: An Identification and Native Plant Forage Guide by Heather Holm
Bees, Wasps, and Ants by Eric Grissell
Happy pollinator planting from Kim Eierman at EcoBeneficial!
Photo: Spring Beauty (Claytonia virginica) – forage source for specialist bee, Andrena erigeniae
Photo credit: USGS Bee Inventory