Cellophane bees make plastic-bag nests and bee soup

Ever on the alert for wild bees, Anna Poladian-Prior is a beekeeper after my own heart. This time, she found a community of ground-nesting bees in the sandy soil just below a redbud tree at her home in Maryland. She managed to snag a couple of great photos and sent them to me.

I’m self-taught when it comes to bee identification, but I came to what I thought was a reasonable conclusion. I was fairly certain I was seeing a bee in the Colletes genus, but I was less certain about the species. But even this was a stretch for me because I’ve never seen a Colletes up close and personal.

Turns out, the dichotomous keys work. When a positive identification finally came from the good folks at BugGuide, I was elated to discover that Anna has a community of Colletes thoracicus. How cool is that?

The cellophane bees

The Colletes (koh-LEE-teez) are known as cellophane bees, polyester bees, or plasterer bees because they secrete a waterproof substance that they paint on the inside of their brood cells. These sacs can be removed from the soil without breaking and are often described as minaiture plastic bags. According to O’Toole and Raw in Bees of the World (2004) making the waterproof lining is quite a physical feat.

The substance is released from the Dufour’s gland and exits their bodies at the base of the sting. So the female curls up in a ball and uses her tongue to capture the drop, then she spreads it on the cell wall. To seal the cell, she builds a “threshold” at the entrance to the cell. Once it dries, she can bend it upward and cover the opening. Then she seals the joints. Think of a tent flap that you can simply zip shut to keep out the water.

This bee speaks with forked tongue

The cellophane bees have a forked tongue which is perfect for spreading the liquid lining. When the substance dries it is impervious to water and may persist in the soil for several years. By keeping the cell contents sealed and dry, the bees protect their young from soil-borne fungus.

A waterproof cell has other advantages as well. Instead of collecting a hard, dry pollen ball, the cellophane bees make bee soup, a liquid concoction of nectar and pollen that is left at the base of the cell. Then the female lays her egg on the wall of the cell above the soup. When the larva emerges, plunk! It falls into the soup and starts to feed. Ah, there’s nothing like diving into a good meal.

A spring bee in a genus of fall bees

While there are about 100 North American species of Colletes, the one Anna has, C. thoracicus, is found as far west as Texas and east to the Florida coast. From there it spreads north all the way to Massachusetts. Throughout the southern part of the range, the bees are active in January and February, but in the more northerly areas they are seen March through June. Although this species is active in the spring, most of the other Colletes are active in the fall.

Although they are strictly solitary bees, one female per nest, they are commonly found in large aggregations. The males can be seen cruising over the ground looking for females in the early part of their season. After mating, the females forage on a number of different plant species. However, some Colletes are specialists, preferring one plant family or even one genus over all others.

Thanks, Anna, for the excellent pics!

Rusty
Honey Bee Suite

A mating pair of cellophane bees, Colletes thoracicus. © Anna Poladian-Prior.

Male Colletes thoracicus on redbud leaf. © Anna Poladian-Prior.

Note: As always, if you have a good photo of a bee in your area, I would love to attempt an identification for you. If I’m not sure of the I.D. I will get help and report back to you. Photos will be published only with permission, so just let me know. I look forward to meeting your bees.