Maryland Grows

I am a horticulture consultant at the University of Maryland Extension’s Home & Garden Information Center (HGIC). Every spring we receive many questions about ground bees that make burrows and holes in lawns and ornamental garden beds. Homeowners are alarmed when they notice many bees flying over an area for several weeks in the spring. They ask questions like: What type of bee is this? Do they sting? Can I mow in the area? When will they go away? How do I get rid of them for good? The bees look intimidating because they tend to aggregate together. It may look like they are tending a busy underground hive, but each bee is typically solitary and digging individual holes. Since a hive is not being defended, the bees are not aggressive.

If you do not know the type of bee you are dealing with, it is concerning. I have a landscaped hill in my backyard that is prime habitat (loamy/sandy soil and good drainage) for ground-nesting bees. For the past several spring seasons, hundreds of bees have flown over an area on my hill. Our entomologist, Mary Kay Malinoski, wanted to identify these bees because many types of bees are important pollinators. Our staff collected samples. The bees were picked up by Lindsay Barranco, a graduate student studying ground bees at the University of Maryland Bee Lab. The bee samples were sent to the USDA Bee Lab for identification.

The ground bees were identified as gentle ground nesters, Cellophane Bees (Colletes thoracicus), also called Plasterer Bees. They are important pollinators of plants and are not aggressive or defensive. They are solitary bees and are not prone to sting humans. They have short lives. After the females lay the next generation and provide food, they will die off. Encourage everyone to tolerate these gentle ground nesters and important pollinators.

Additional Resources

• Mining Bees – Lawns | Home & Garden Information Center
• Meet a Pollinator: Colletes thoracicus | Lindsay Barranco
• Pollinator Gardens | Home & Garden Information Center
• Spring Sunshine Heralds the Appearance of Plasterer Bees: Colletes | Bug of the Week, Michael Raupp, Ph.D., University of Maryland

By Marian Hengemihle, Horticulture Consultant, Certified Professional Horticulturist, University of Maryland Extension Home & Garden Information Center

Do you need help to identify bees or other insects found around your yard or home? Send clear photos of your insects to HGIC’s Ask Extension.