09/29/2025
Did you know that some male bees dig or excavate burrows to sleep in overnight? I didn’t either until I visited Santa Rosa Island a few years ago to search for Colletes hyalinus gaudialis (Delightful Hyaline Cellophane Bee). I expected to find the males sleeping on plants, as I’ve seen them do on the mainland. But after searching at dusk, through the night, and into the early morning, I wasn’t able to locate them.
By complete chance, I stumbled across a small aggregation of males one evening digging into the soil (2nd photo). Early the next morning, the males’ faces slowly emerged from the burrows where they had spent the night. They all appeared to have slept upside down, in a position similar to how they develop inside their cocoons (1st photo). As far as I’m aware, this is the first time this behavior has been documented. Santa Rosa Island is incredibly windy, and I wondered whether the high winds might be the reason they chose to sleep underground.
Last year, on the mainland of California, I discovered another male bee from a completely different family exhibiting the same behavior. At first, I didn’t realize they were males, since I was in the area looking for a different bee. I quickly snapped a few photos without really looking at them and moved on. It wasn't until this year, while reviewing my photos, that I realized I had captured male Andrena cerasifolii (Cherry Plum Mining Bee) emerging from burrows in the morning (3rd photo).
I thought there was a chance they might be entering female burrows in hopes of mating, but after returning to the site this year, I observed the males entering the burrows midafternoon, when it cooled down, and staying in them until it warmed up the next morning. Oddly enough, I’ve seen a male of this species sleeping on plants like I would have expected them to in other areas.
This could be an adaptation to specific local conditions, or part of a broader pattern we haven’t yet recognized.
If you’d like to read more about the Colletes hyalinus gaudialis on Santa Rosa Island, you can pre-order a copy of my upcoming book, "The ABCs of California's Native Bees," here: https://www.heydaybooks.com/catalog/abcs-of-californias-native-bees/
