The Alkali Bee (Nomia melanderi)

By Beatriz Moisset and Vicki Wojcik, Pollinator Partnership

Alkali bees are ground-nesting bees native to the western and southwestern United States with a preference for salty soils. To the untrained eye bees in the genus Nomia look similar to honeybees. They are slightly smaller than the honeybees and have a more elaborate striping pattern: black abdominal segments are separated with gorgeous iridescent stripes made of enameled scales.

Belonging to the family Halictidae, alkali bees share some traits with other sweat bees, most notability their complex nest design where a network of tunnels leads to egg chambers. Although they are solitary, with each female building its own burrow and brood chambers, they enjoy each other’s company and often live in large aggregations on salt flats or in open patches of salty soils. These aggregations of alkali bee nests can grow to an enormous size if the conditions are right, with many thousands of individual females nesting side-by-side. In some cases, sisters may even share nests. This life-style is called semi-social living and is considered by some scientists as a step in the evolution of true social behavior seen in honeybees.

One species in particular, Nomia melanderi, has proven invaluable for the pollination of alfalfa and farmers have become adept at creating the right conditions for their nesting near alfalfa fields. Its services are put to use as pollinator and it is managed for this purpose using habitat conservation and set-aside areas near farms and ranches.

Alkali bees are happy in a climate where honeybees would not fare very well. Their choice nesting sites, soils saturated with salts, are not suitable for agriculture. Most importantly - they are willing to pollinate flowers of the pea family, such as the introduced alfalfa, that give a floral “slap-in-the-face”. Alfalfa flowers require a specialized technique because of their complicated structure; they have to be “tripped”. The male and female parts of the flower are not exposed but enclosed inside the lower petal, the “keel”, so called because of its shape. The bee has to land on it and put a little pressure that snaps it open exposing the anthers with their pollen and the stigma. If you observe pea flowers, you may recognize the ones that have been visited by pollinators because of their exposed anthers and stigma. Honeybees do not like to perform such operations, but bees of the genus Nomia have perfected the technique and are so efficient that they can visit and pollinate more than a thousand flowers a day.

For many years the alfalfa growers of the American West, especially in Utah benefited from the pollination services of these bees without realizing it. Alfalfa became a very important crop in a land with a harsh climate and rather salty soils that did not seem fit for agriculture. They only became aware of these pollinators’ value when they started plowing over their beds to expand the cultivated fields or resorted to pesticides. These two measures proved catastrophic to the industrious bees and the alfalfa yields dropped dramatically.

Alfalfa farmers soon realized that they were killing the species that kept them productive and changed their strategy. In the past fifty years, alfalfa farmers have been creating the right conditions for alkali bees. The Walla Walla Valley in Washington is famous for being one of the few regions where farmers farm both alfalfa and bees. This learning process required finding the right kinds of soil and amount of salt, the adequate drainage and sun and shade combinations. Nowadays there are books with detailed instructions on how to build an alkali bee nesting bed by using a waterproof layer at the base, successive layers of gravel and sand; a combination of salts on top to seal the moisture underneath and buried pipes to produce the right amount of moisture.

Alkali bees, along with blueberry bees, some mason bees and squash bees, belong to the ranks of native pollinators whose value is appreciated and put to good use by farmers.

For Additional Information

• Mader E, Vaughan M, Shepherd M, and Hoffman Black S. 2010. Alternative Pollinators: Native Bees
• Cane JH. 2007. Alkali Bee. In: Shimanuki, H., Flottum, K., Harman, A., editors. ABC & XYZ of Bee Culture. 41st edition. Medina, OH. A.I. Root Company. p.11-12. Summary available.
• Buchmann SL and GP Nabhan. 1997. The Forgotten Pollinators. Island Press, Washington, D.C.
• O’Toole C, and A Raw. 1999. Bees of the World. Blandford, London, U.K.
• Stephen WP. 1959. Maintaining Alkali Bees for Alfalfa Seed Production. Station Bulletin 568 Available (PDF).