~ Kentucky Pollinators and Backyard Wildlife ~
Mining bees or miner bees are some of our earliest native bees to become active in the spring. All of the bees in the genus Adrena are commonly referred to as mining bees. It is estimated that there are over 400 species of Adrena bees in North America. A mining bee is a little smaller than a honey bee and tends to be dark colored with pale bands of hair on their abdomen. Many of the species are hard to tell apart which is why they all share the same common name of mining bees.
Like most of our native bees, mining bees are solitary bees and live underground. They dig their nests in areas with semi-loose dirt and sparse vegetation. Mining bees are most active in the early spring. They emerge when there are still relatively few pollinators active which makes them very important pollinators of early blooming plants.
Many species of mining bees only collect nectar and pollen from a single family of plants and sometimes only a single genus or species of plant. Mining bees can be important pollinators of apples, blueberries, strawberries and a few other early flowering crops.
In Kentucky, March and April are good months to look for mining bees. The best way to find them is to watch areas in yards or gardens where there are patches of bare ground between the grass or other vegetation. If you see holes that look like someone jammed a pencil into the ground or small bees busily flying low over an area of bare ground, then there is a good chance that you have found mining bees.
Mating occurs soon after the miner bees emerge. The females then begin to dig their nests. Each female will dig her own nest which usually consists of a single main tunnel with up to a handful of short side tunnels. Each nest is usually less than 10 inches deep. Although mining bees are solitary, you can often find many individual nests fairly close to each other. The bees aren’t cooperating in any way, they just aren’t territorial and are all taking advantage of the good nesting habitat.
After the female digs her nest, she secretes a waterproofing substance from a gland on her abdomen. The substance soaks into the soil. The female uses a special, flat area near her rear to rub the soil until it is polished into a waterproof wall. Once the side tunnel is complete, she’ll gather pollen and nectar which she forms into a small ball. Each side tunnel gets its own ball of nectar and pollen. On top of each ball of pollen and nectar, she lays an egg and then seals the tunnel.
Most of the life cycle of the mining bee takes place underground in the sealed nesting tunnel. While in the sealed nesting tunnel, the egg will hatch into a larvae. The larvae eats the stored pollen and nectar and goes through several larval stages over the course of the summer. Before winter, it molts into what’s called a pre-pupal stage. The pre-pupal stage of the mining bee is essentially the same stage as a butterfly is in as a chrysalis. In the spring, the mining bee will finish pupating and then emerge to mate and start the cycle over again. Often any given species of mining bee will only be active above ground for a few weeks each year.
If you find mining bees nesting in your yard, don’t have to worry about them. They are very gentle and rarely if ever sting. As solitary nesters, they don’t have the force of the hive, like honey bees have, to back them up. So if a predator attacks, their best defense is to run away.
Spraying them with pesticides to get rid of mining bees is not recommended, nor is it usually successful. Mining bees will continue to find and use the area as long as you have the right habitat for them. Instead of trying to get rid of them, the best option is to enjoy them. Know they are providing an important pollination service, are providing free aeration for your yard, aren’t dangerous, and will likely disappear again in a few weeks.
Shannon is a beekeeper, farmer, wildlife biologist, and author. She owns Grassy Roads Farm and Busy Bee Nursery & Consulting. Busy Bee Nursery & Consulting specializes in plants and habitat consulting services for honey bees, native pollinators, and wildlife conservation. She is the author of Plants Honey Bees Use in the Ohio and Tennessee Valleys. Shannon also writes a blog about Kentucky Pollinators and Backyard Wildlife and a farm and nursery blog that features stories of life on the farm, tips for attracting pollinators and wildlife, and highlights of different plants for pollinators and wildlife.