Mining bees are wild bees that live underground

Once you start studying the pollinators in your garden, you will see many different types. If you start recognizing some of your visitors, you will look forward to seeing those old friends and indentifying new ones. People seem to care more about the things they can put a name to, so I encourage you to spend some time with identifications.

The different species within the genera are very difficult to discern, but most people can learn to identify down to genus. That in itself is an accomplishment!

For instance, take the genus Andrena. The 1300 species in this genus are also called “mining bees” because they nest in the ground. Like most bee species, they are solitary, which means that all females are fertile and each one builds a nest by herself, provisions the nest with pollen and nectar, and lays the eggs. Unlike a honey bee colony, there are no workers, no honey production, nor any comb building.

The eggs hatch and the young bees progress through the larval stage to the pre-pupal stage before winter sets in. During the winter they remain in the pre-pupal stage until early spring when they complete their metamorphosis into adult bees, both male and female. The adults emerge from the ground, mate, and the females of this new generation begin to build their homes in a new underground chamber.

Solitary bees are often oligolectic, and Andrena bees are no exception. An oligolectic bee is one that collects pollen from only a select few plant species. Often these plants are very closely related—in the same family or even the same genus. In fact, some species of Andrena bees are monolectic, meaning they collect pollen from one—and only one—species of plant. It is easy to see that if that plant becomes rare or extinct, so does its pollinator. No wonder our wild bees are in trouble!

Andrena bees range from about 8-17 mm long. The females in this genus can be distinguished from other bees by the velvety patch of hair between the eyes and the antenna bases. They also have well-developed corbiculae—or pollen baskets—on the sides of the thorax and hind legs. Since the males do not collect pollen, they are not as hairy as the females. The males are also shorter and narrower than the females.

Because Andrena bees build their nests underground, they are adversely affected by farming practices such as tilling, plowing, disking, and spading. They also do not thrive in ground that has been completely cleared of vegetation because they like nesting sites that are protected from weather extremes by bushes or trees. Heavy mulch is also bad for Andrena bees because the females are not able to dig through mulch to get to the soil.

Needless to say, insecticides readily kill Andrena bees and herbicides kill the plants on which they are dependent. Maintaining a pesticide-free garden with plenty of bare soil and many plant varieties—including native species—is the best way to attract and conserve most native bees, including Andrena.

Rusty

Andrena fulva (female). Flickr photo by Mick E. Talbot.
Andrena fulva (female). Flickr photo by Mick E. Talbot.
Adrena haemorrhoa (female). Flickr photo by Mick E. Talbot.
Adrena haemorrhoa (female). Flickr photo by Mick E. Talbot.
Andrena (male). Flickr photo by jbaker5.
Andrena (male). Flickr photo by jbaker5.

Comments

Maureen
Reply

I discovered a hole the size of a basketball where some animal had unearthed a nest. On the ground
were large pieces of combs that appear empty. Bees are still coming in & out of this hole from deeper in the ground. Will the bees dig out if I fill in the hole? Did the animal excavation eliminate the survival of this particular nest?

Rusty
Reply

Maureen,

To me it sounds like a wasp nest. Are the combs round like plates or some other shape? If the insects are still coming in and out, they may be able to recover from the attack. If you fill the hole too tightly, they will likely become trapped. If you fill it loosely, they can probably dig through it. If they are wasps, and if you live in a place with cold winters, the colony will die out with the first freeze.

Karen
Reply

While mowing today, I discovered a large hole in my yard, at least as big as a softball, with many., many little bees going in and out of the hole. They are not yellow jackets or sweat bees. One of the little buggers stung me through my thin top! I don’t want to destroy them, but I have to mow there or it will be a jungle! I live in Kentucky. Do you have any advice?? Can you send an email to me to help me decide what to do?

Rusty
Reply

Karen,

It sounds like a semi-social bee that is using a common entrance area. I’m guessing they have individual nests coming off separate tunnels under the ground. Or it may be a primitively eusocial type of bee. In any case, fully 70% of the 20,000 species of bee live underground, so it is difficult to say what it is. You say it’s not a sweat bee, although I am less sure of that. There are something like 500 species of sweat bee in North America. They are very different from each other and many of them have some degree of sociality, like what you describe.

These bees are important pollinators and part of a healthy ecosystem, so it makes no sense to destroy them. The nest will soon go inactive as cold weather approaches. Put on some heavier clothes and just mow over it. Or mow around that area. Sometimes conserving valuable resources causes some amount of inconvenience in our lives, but imagine where we would be without them.

Arya
Reply

In my chili pepper field (Indonesia), there are some insect like bees. It’s black, digging on soil, making its home inside, eating caterpillar that eat my chili leaf (HELP ME A LOT). It’s solitary I think, but many of them, hundred maybe thousand. Soil that it dig have some like earth worms shit, it’s also like heat of sun, because on field full of weed (shade from sun), the population is small, it’s also pollinate my chili. That bee resist Deltamethrin, Chlorpyrifos, Imidacloprid, Abamectin, and even tobacco leaves extract, because it’s population growing even when I spray my chili field against leaf mites (on recommended dosage of course), but sadly, it’s gone if raining. It’s not aggressive even when walked near them (but of course who want to touch them!), is that a real bee family or some kind of other beneficial bugs??? Help me please. Oh yeah, it is sized around 1,5 cm long.

Rusty
Reply

Arya,

It’s impossible for me to say for sure, but if it looks like a bee, burrows in the soil, lives in communities, likes full sun, pollinates chilis, and eats caterpillars, my guess it that it is some type of wasp. It’s not a bee if it eats caterpillars. That you have any living thing in your field is a miracle, given your spray regimen.

osacar.viera
Reply

cuando se estraee la miel de estas abejas de la tierra. o conocida como merino aca en la campaña .

Rusty
Reply

Mining bees are not honey bees and they do not produce honey that can be harvested. They just mix nectar with pollen.

Stacy
Reply

Hi!
Thank you for this wonderful information. I have a question–can I put rocks down on top of where the mining bees came out this spring? Will the bees be ok? I will leave spaces between the rocks for them to get in and out, but it won’t be the stretch of dirt that was there before. (I won’t use gravel; the rocks are softball-to-basketball sized.) And once the bees have come out of their holes and stopped buzzing around, is that the time to put the rocks down? Thank you!

Rusty
Reply

Stacy,

Is that like Monmouth College in NJ?

Bees definitely like areas of bare dirt, but as long as you leave space between the stones I think they will be okay. It depends to some extent on the type of bee you have. Some nest randomly, wherever they find room. Others like to build large, extended communities where they benefit from each others ability to find off intruders.

As soon as they emerge they will mate and start to build more nests. So as they are emerging is probably the best time to add the rocks. At least you know where the old and new openings are so you won’t cover them up.

Stacy
Reply

That’s Monmouth College as in Monmouth, Illinois. The same Scottish Presbyterians who founded Monmouth College (now Monmouth University) in New Jersey kept moving west and founded Monmouth College out here in the prairie, where, apparently, mining bees are very happy!

Thank you so much for your helpful response. I will get out there this coming weekend to try to reposition the rocks selectively and decoratively! I really, really, really appreciate the quick and useful answer to my question. I have been very worried about those bees, who have been living here for at least nine years. Thanks!

Rusty
Reply

Thanks Stacy! I once took a writing course at Monmouth College (it was college at the time) in NJ, so I was wondering. Enjoyed the history lesson!

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