The genus Colletes is a large group of ground-nesting bees with more than 450 species worldwide. Although they tend to be solitary nesters, they will often nest in close aggregations. Female cellophane bees create nest cells in underground burrows in sandy soil, which they line with a cellophane-like, waterproof secretion from their abdominal glands, giving rise to the various common names of this group; they are referred to as cellophane, polyester or plasterer bees. 

This past Saturday afternoon, I came across a sandy area in the sun at the edge of an abandoned cranberry bog that was swarming with bees. After repressing my initial fear response, and moving in slowly for a closer look, I realized these were not yellow jackets, as I’d originally feared, but rather a group of ground nesting bees newly emerged from their nests. I was able to sit on the ground adjacent to their nests and closely observe these non-aggressive bees. (Note: Yellow jackets are also ground nesters, but are wasps, not bees; they are also considerably more aggressive and I would not have chosen to sit down in the middle of a swarm of them.) Although I can’t be 100% sure, as there are multiple species of cellophane bee in our area, I believe what I encountered was a group of unequal cellophane bees (Colletes inaequalis), which are one of the earliest bees to emerge in the spring and are one of the most abundant ground nesting bees in northeastern North America. 

C. inaequalis is a common species of cellophane bee native to North America, found from Nova Scotia to Minnesota and south to Georgia, and is active from March to July. Warm sunny days in March warm the soil and trigger the emergence of the male cellophane bees. They can then be seen swarming the ground in the area of a congregation of nests waiting for the females to emerge so mating can take place. From there, the males and females go their separate ways: the males fly off to live out their short lives sipping from freshly opened tree blooms, while each female will work alone excavating her own nest. She will create a tunnel, up to a foot-and-a-half-deep and as wide as a pencil, straight down into the ground. Eggs will be laid individually in brood cells dug into the sides of the tunnel. Each brood cell will be lined with a natural polyester secreted from her abdomen, which she spread on the cell walls using her paintbrush-shaped tongue. The female then lays a single egg into each brood cell, which has been packed with nectar and pollen, before sealing the cell off with additional polyester secretions. This lining not only helps protect the larvae from fungal disease, but it also creates a waterproof barrier, allowing these bees to occupy areas prone to flooding with little damage to the developing insects.