Stopping at dusk to marvel at a huge meadow, densely covered in literally millions of low-growing blooming lupine (Lupinus breweri), I looked down at some scattered yellow Indian Paintbrush plants (Castilleja arachnoidea) and noticed a group of bumblebees clumped on the elevated flower stems. Looking about, I suddenly realized there were hundreds of bumblebees gathered on the numerous paintbrush plants near me. When I bent to get a closer look, they were all quite lethargic, and only moved if I got very close or inadvertently knocked a nearby stem. I realized that with the colossal amount of lupine in bloom, pollination would require a giant population of pollinators, and I guessed that these were simply some of the legion of local "workers" hunkering down to rest for the night. At first I thought they would all be males, as I figured the females would return to their nests at night. But in fact, a number of them had what looked like thick round wads of orange pollen packed onto their legs, so I assume that means females were present.

If anyone has witnessed similar phenomenon, or has knowledge of how large bumblebee populations spend the night at the peak of pollen harvest, I'd love to hear your ideas on this.