Wild pollinators move into their new bee habitat wall

Get up close and personal with solitary bees as they begin to inhabit the 24’ earthen wall and interactive cabinet at College Park’s Arboretum Outreach Center, a tranquil garden next to Byrd Stadium. Guest artisans and I designed and built the structure this summer with the help of many hard-working volunteers. Funding for the project came from Mike Raupp ‘The Bug Guy’ as part of UMD’s nationally acclaimed outreach program. The main purpose of the bee wall is to raise public awareness of wild pollinators and to facilitate monitoring of campus bee populations.

Earthen pollinator wall with the Audio Bee Cabinet at UMD's Arboretum Outreach Center. Photo by Lisa Kuder.

Aptly named Dwelling: Paint Branch Creek homage to the 17 mile long Paint Branch stream that flows through Prince George's County, the habitat wall mirrors the curves and layered soil horizon of a meandering river bank. Vertical earthen surfaces such as these are prime real estate for many ground nesting insects. If you look carefully, you will find premade holes of various sizes in each band of clay to attract different types of pollinators. Embedded in the wall is a beautiful pollinator cabinet that enables visitors to observe and listen as cavity or wood nesters provision their nests. Within just one week of completion, multiple species of bees and wasps had already started to move in.

Chopsticks were used to poke holes of various sizes in the contrasting colors of clay to attract multiple species of solitary bees and wasps. Photo credit: Sarah Peebles

Illustration of the solitary bee life cycle depicted on the Audio Bee Cabinet by Sarah Peebles with pyrography by Mary-Ann Alberga, assisted by Rob Cruichshank (electronics) and Jennifer Rong (cabinetry). Photo by Lisa Kuder.

But wait a minute . . . won’t I get stung? Solitary bees and wasps are non-aggressive unlike their pesky cousins the yellow jackets. Plus, they don’t defend their nests like social bees (honey bees and bumble bees). In MD alone we’ve over 400 species, most all of which are solitary, meaning each female provides for her own offspring. Don’t be fooled by the word solitary though as many species are gregarious preferring to live in large groups. It will be exciting to see who occupies the wall and how their populations fluctuate over time. Beginning next spring, regular updates will be posted to this blog documenting colonization rates.

What kind of bees do we expect to move into the earthen wall? Our target genus is Anthophora. According to the USDA ground nesting species make up at least 70% of the bee population. Yet bee expert Sam Droege estimates that the actual number might be as high as 95%. While it is more common for bees to nest in horizontal sites, some genera such as Anthophora prefer dry perpendicular surfaces. They tend to form large nesting aggregations on the face of steep cliffs, upturned tree roots, creek beds and, yes, cob structures. Maryland is home to 6 species of Anthophora, 2 of which are fairly common, native A. abrupta and naturalized A. plumipes. In a modern landscape, undisturbed nesting sites for Anthphora and many other bees can be lacking.

A nest aggregate of Anthophora abrupta  in a local cob wall. This is one of the few species in the region that builds turrets or chimneys. Biologists believe that these additions regulate the temps of their nests. Interestingly, it has been noted that dry seasons result in shorter chimneys. Photo by Charley Eiseman.

Anthohora abrupta entering a turreted nest. These fast-flying bees resemble small bumble bees and are excellent pollinators of several valuable food crops. Males don mustaches for collecting parsnip oil to woo the females.  Photo credit: USDA Scott Bauer.

Wood nesting bees make up the other 5 - 30% of the population. Rather than nesting in the ground they are drawn to soft-pithed twigs and beetle tunnels in dead trees. They will also readily use blocks of wood with man-made tunnels like those found in the wall's bee cabinet. Thanks to Plexiglass sheets, visitors can observe mason bees and blue orchard bees (Genus: Osmia), yellow-faced plaster bees (Genus: Hylaeus), Megachile spp. and beneficial predatory wasps line and cap natal cells with their preferred nesting materials (leaves, mud or resin). Bring a pair of earbuds so you can plug in to the solar powered amplifier and hear the fascinating noises these small, amazing creatures make while at work. 

An interior shot of the bee booth.Plug in your personal headphones or earbuds to listen and observe as solitary bees and wasps build their nests. When you're finished, please remember to shut the door so the residents don't bake in the sun. Photo credit: Rob Cruichshank.

A peek at some of the nesting activities taking place within the bee cabinet. Isodontia spp. commonly called grass nesting wasps are utilizing the top 2 tunnels. They are a gardener's best friend, as they help control insect pests. Each cell, comprised of a stunned cricket and an egg, is partitioned with grass. Finally, the solitary wasp caps her brood with a tuft of grass that resembles a broom. The 3rd tunnel from the top is filled with cells from a resin bee belonging to the genus Megachile.  Look closely and you will see bees in the various stages of  development (egg, larva, pupa and adult). Photo by Lisa Kuder.

Also of interest is the cob construction of the wall. Cob or cobb is a natural building material made of clay, sand and a fibrous organic material (typically straw). This ancient building technique is still used throughout the world and has recently experienced a revival in the U.S. as the demand for sustainable, green architecture grows. Approximately 7 tons of locally sourced materials were used to build the habitat wall. From the bottom up nearly all of the materials are repurposed; including urbanite (broken concrete) and subsoil from a campus construction project, cedar from an old playset and the corrugated roof panels made from 50% recycled fibers. River rocks salvaged from earlier construction work were used to protect the upper surface of the wall from the elements.

Local green builder  Zak Kahn with a fresh batch of cob. The basic 'recipe' for cob is one part clay to one part sand. As these ingredients are mixed with a gas powered tiller, water is added until the consistency is thick but sticky. The final ingredient chopped straw increases the tensile strength of this earthen building material. Photo by Lisa Kuder.

Undergrads from Dennis vanEngelsdorp's Bee Lab embed river rocks into the top surface of the wall to slow the natural erosion process by reflecting water from the cob. Photo by Sarah Peebles. 

A bit more about the human resources: Sarah Peebles a Toronto based sound and installation artist is the originator of the audio bee cabinet part of a media outreach program called Resonating Bodies. Engaging all of the senses enables the user to experience the secret lives of bees in a fuller more intimate way. Incorporating the cabinet into cob was a way of expanding opportunities to explore the meaning of biodiversity.  Ed Raduazo, a local cob expert, was instrumental in this process by teaching the crew how to mix and build with cob using a gas powered tiller and hand tools. His passion for keeping this important building technology alive for future generations inspired all during the physically intensive work.

Ed Raduazo showing the crew how to layer cob so it doesn't sag. In the Mid-Atlantic region where humidity levels are high, only 12" or so can be added per day. Photo by Sarah Peebles.

Sarah Peebles and volunteer Monette Bailey from UMD's Center for Leadership & Organizational Change shape the wall with wooden floaters. Photo by Lisa Kuder

Additional acknowledgements . . . a thousand thanks not only to Mike, Sarah and Ed but also to student helpers from Dennis vanEngelsdorp's Bee Lab: Adam Kellermann, Byron Mariani, Mike Gladchuk, Marina Peterson and Sidharth Ganesan, and to Eric Kuder for designing and constructing the weather guard, the entire staff at the Arboretum Outreach Center especially Carin Celebuski and Michael Carmichael for their patience and support throughout the whole process, Zak Kahn for his expertise with cob construction, Capital Projects for donating urbanite and clay, LCI Recycling for donating and delivering masonry sand and to Sam Droege for introducing me to Ed and Sarah, providing occasional cob advice and creating a buzz about wild bees.

Please stay tuned for future updates on UMD's new habitat bee wall. In the meantime, please send any questions/comments about this project to:

Lisa Kuder

PhD student

Dennis vanEngelsdorp Bee Lab

University of Maryland

Entomology Department

4112 Plant Sciences Building

College Park, MD 20742

Email:  lkuder@umd.edu