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Alkali bees, the alfalfa specialists

Honey bees aren’t always the best bug for the job, and that is certainly the case when it comes to pollinating alfalfa. Honey bees do not particularly like alfalfa pollen and colonies don’t thrive when it is the sole source of their protein. But what really bothers the honey bee is the tripping mechanism of the the alfalfa flower. When the bee reaches down into the center of the flower to sip the nectar, the flower releases its pollen with an explosive spring that delivers a good whack to the honey bee. To avoid the direct hit, honey bees learn how to “steal” the nectar from the side of the flower. While this works for the bee, it fails to pollinate the flower.

Underground nesting tunnels. Art Cushman, USDA; Property of the Smithsonian Institution, Department of Entomology, Bugwood.org.

As it turns out, a solitary ground-nesting bee, Nomia melanderi, is the very best pollinator for this important crop. The tripping flowers bother her not, and she pollinates the fields with gusto. Slightly smaller than a honey bee, with a bluish-, yellowish-, or greenish-and-black stripped abdomen, these bees live in vast communities. Even though each female raises a family by herself in her own home, she is part of an impressive neighborhood.

These bees are known as alkali bees because they prefer to nest in soil with a salty crust which covers a damp, saline soil beneath. The salty soil holds moisture, discourages plants and their annoying roots, and is inhospitable to some ground-dwelling organisms. The perfect home is not easy to find, but once established, the alkali bees will thrive for year after year if the soil remains undamaged and a good nectar source remains nearby.

The ground above a Nomia nesting area. Bob Hammon, Bugwood.org.

In the northern states, alkali bees produce only one generation per year and in Washington, the active period coincides perfectly with the alfalfa bloom. Although alkali bees are known to be polylectic—meaning they will forage on a variety of different plants—when a good supply of alfalfa is nearby they can thrive on it alone.

In the late spring, the males emerge first. They spend their days patrolling the nest areas looking for females, and they often spend nights in groups in the nearby foliage. Once a female mates—at two or three days old—she begins the task of preparing her nest.

As shown in the diagram at right, the female digs a tunnel straight down in the moist soil, two to eight inches deep. She prefers a pre-dug hole, so if she finds one, she cleans it up and makes her home in that. She divides the vertical tunnel into seven to twelve branches, each terminating in an oval cell. The female packs the cell walls with fine particles of soil and then coats it with a moisture-resistant material she secretes. Once complete, she provisions the cell with a pollen sphere on which she deposits one egg. She then seals the cell and moves on to the next.

Each female lives four to six weeks and the entire active season lasts about 60 days. To learn about the large threat facing these bees in Washington state, please see my earlier post: “Alkali bees face death by highway.”

Nomia melanderi, the alkali bee. Photo by Carol Davis.

Comments

bill castro
Reply

GREAT ARTICLE!!! Saw one of these girls buzzing on dandelions yesterday…even got a good picture!!

Rusty
Reply

So Bill, do we get to see it?

Erie Smith
Reply

Nice article for its informative contents. It was so amazing how these flying insects Alkali bees built their nest under the soil…I’m so impressed!

phil gladding
Reply

I really do enjoy this website. I check the pc every morning as soon as I get up to see if there is anything new. I started beekeeping last year with 2 hives and get so much information from you. Thanks, Phil

Merryn
Reply

How interesting! I have never heard of alkali bees before and just love the pictures/diagram. We do live in a wonderful world.

Jeanette
Reply

I didn’t realise that bees could be ground-dwellers. Your article prompted me to discover that Australia has over 1500 species of native bees, including alkali bees. Thanks for teaching me something new!

Rusty
Reply

Jeanette,

About 75% of all bee species are ground-dwellers, something few people are aware of. I’ve seen many photos of Australian native bees and they are exquisite.

Heather
Reply

Do alkali bees normally nest in central ohio? I just found one yesterday…poor thing froze in the cold night air.

Rusty
Reply

Heather,

The alkali bee is found west of the Rocky Mountains in deserty alkaline soils. In any case, the adults are only active in June and July. It spends most of the next ten months as a prepupa in a nest in the ground.

Donna Seidel
Reply

In the 50s, in north central Kansas, we had large colonies of what we called “ground bees.” On our farm, they dug their holes in the chicken yard which was right next to 120 acres of upland alfalfa. When wheat replaced alfalfa, the bees left.

Rusty
Reply

Donna,

That is really sad, but there is no food for them in a wheat field.

Neshan
Reply

Where I’m from, in the northern foothills of Los Angeles (specifically the northern boundary of the city of Glendale), we have tons of Alkali bees. We have lots of lavender, rosemary, as well as different chaparral-type plants lining the long driveway and front yard. They have their tunnels lining all of our walkways, and it’s wonderful to watch them forage. Thanks for the awesome post. These bees deserve more attention, for sure.

Rusty
Reply

Neshan,

It’s rare that anyone knows what they are. I’m so glad you have them and like them! They’re my favorite native bee.

Cynthia
Reply

I have raised various bees off & on for *cough*, years, & have a love for all insects etc. What I do on my land is mark nest sites with those small landscaping flags, the 3″×3″ ones from box stores. This way I can hopefully avoid me injuring them with my activities. (Can’t say my large animals pay attention! ) I also mark other various eggs, nests, etc. with a ribbon. (Such as mantid egg cases.) I’m thinking since we all read this website, there are other earth stewards! Thnx for being awesome!

Rusty
Reply

Thanks, Cynthia.

Carol Davis
Reply

Thanks for showing off my Alkali Bee photo and thanks for the great web site. Keep up the good work.

Rusty
Reply

Carol,

Since that post, I’ve had several opportunities to photograph alkali bees in Eastern Washington. So now I have literally hundreds of shots, but yours are truly amazing. Thank you.

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