Minnesota Bee Researchers Document the Natural History and Biology of a Rare Specialist Cellophane Bee
- Heather Holm
- 5 days ago
- 4 min read
Updated: 4 days ago
For much of the five hundred and twenty or so bee species that occur in Minnesota, little is known about their nesting biology and plant preferences. In their new publication titled The nesting biology and foraging distance of the bee Colletes andrewsi (Hymenoptera, Colletidae), a rare specialist of Heuchera spp., Minnesota bee researchers Marissa Chase, Zach Portman, and colleagues at the Department of Natural Resources uncover one of those mysteries. Their publication details new information about the life history and biology of a rare ground-nesting pollen specialist cellophane bee, Colletes andrewsi population discovered Crow-Hassan Park Reserve in Hennepin County in 2025.
A Bee With a Narrow Diet
Colletes andrewsi is a floral specialist, and in Minnesota, it relies exclusively on the native prairie plant, Heuchera richardsonii (prairie alumroot) for pollen. Unlike generalist or polylectic bees that visit a variety of flowers, this bee’s diet is tightly linked to the presence of its preferred pollen host plant. In the large diverse prairie at Crow-Hassan, the researchers found that C. andrewsi females were never observed foraging on any other flower, making the conservation of H. richardsonii in sand prairie habitats critical for the bee’s survival.
Life Belowground: Nesting Habits
Their publication also details this specialist cellophane bee’s nesting activity and specifications, revealing that females dig shallow, simple nests, just 1.3 to 6.9 centimeters (0.5 to 2.7 inches) deep, along sandy, partially vegetated trails.
Each female’s nest contains a main tunnel ending in a cluster of brood cells, where, provisioned with a liquid mixture of pollen and nectar by a female, the larvae develop. Many females build multiple nests in a single season, sited in close proximity to each other. Moreover, they often return to the same nesting area and nests where they were reared, a behavior known as philopatry. Therefore, if undisturbed, each following year, succeeding generations use the same nesting location.
Foraging Far and Wide
Despite their small size, these bees have an impressive foraging range. Using methods developed by bee researcher Nick Dorian, Chase and Portman employed a mark-recapture method to track the activity of each bee at Heuchera flowers, around the nesting aggregation, and in emergence tents. Using a non-toxic marking pen, they assigned and marked each bee with a unique three-color combination of dots on their thorax. Round metal tags were annotated using the same unique color combination and placed next to each nest entrance.
Subsequent recapturing of the foraging marked bees demonstrated that females can forage over 300 meters (328 yards) from their nests, with an average trip of 143 meters (156 yards). Even with abundant flowers nearby, individual bees often return to the same patch of blooms, demonstrating remarkable memory and fidelity to specific foraging spots.
Perils and Predators
Colletes andrewsi, like all bees, has a number of natural enemies. Their shallow nests make them vulnerable to predators like the thirteen-lined ground squirrel, which was caught on camera digging up nests and eating both larvae and adult bees. In 2024, a year prior to the study commencing, naturalists documented a cuckoo bee, Epeolus interruptus, investigating and monitoring the nests; however, none were observed during the study period. Furthermore, competition among females is fierce, with frequent fights and even nest usurpation, where one female takes over another’s nest.
Mating Mysteries
Mating takes place exclusively at Heuchera flowers, not at the nests as is seen in some related species. Males, larger than females and emitting a distinctive musty-citrus odor, patrol flower patches in search of mates. Most mating attempts are brief and often unsuccessful, but this flower-focused mating strategy ensures genetic mixing across the landscape.
Conservation Implications
The story of Colletes andrewsi highlights the importance of understanding the life histories of rare and specialized pollinators. Their dependence on specific plants tied to specific habitats, and preferred nest site conditions makes them especially vulnerable to habitat loss and environmental change. Conservation efforts that protect and restore native Heuchera populations and undisturbed sand prairie habitats are essential for the survival of this remarkable bee.
By shining a light on the secret lives of bees like C. andrewsi, scientists hope to inspire more research and action to safeguard the diversity of bees that keep our ecosystems thriving.
Follow Up Questions
For future work and research, two questions the authors endeavor to answer are:
1) If you plant Heuchera richardsonii in a prairie restoration will Colletes andrewsi find that host plant population? If so, how long will it take them? 2) Colletes andrewsi hasn’t been documented in gardens; would this bee show up if a population of the host plant, Heuchera richardsonii, was planted by gardeners? Note: as far is known, Colletes andrewsi does not visit any ornamental Heuchera varieties or cultivars.
Article photos: Heather Holm
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