You’ve come across what looks like ant hills but the holes seem too large. There are many of them together in the area but you don’t see any ants. Watch for a moment and you’ll see bees buzzing around, going in and out of the holes, and you may even see the rather appealing face of a bee peering out from the top of a few holes. If you startle it (or try to get a photo!), it will quickly withdraw back out of sight. I recently came across a colony of the native ‘polyester bee’ or ‘unequal cellophane bee’ Colletes inaequalis (tentative ID) in Avon, CT.
This is a ground-nesting bee. They are solitary, or have one nest (hole) per female, but the nests are in colonies. People often become alarmed when they notice bees nesting in the yard or in areas where people or pets are active. In fact, polyester bees rarely sting and they are important native pollinators so they should be protected and left undisturbed during their spring nesting period. To discourage them the next season, cultivate grass or other plants in the area in the late summer or fall because bare soil is prefered. Most of the time, they are nice to have around because of their role in pollination. They can even be more effective pollinators than honeybees for some plants when they have good nesting areas. Try to put up with their activity for a couple of months and they’ll be inactive for a good part of the season. Avoid the use of insecticides.
The polyester bee pollinates a wide range of host plants including, but not limited to, Aesculus, Amelanchier, Anemone, Aronia, Cercis, Crataegus, Erythronium, Hepatica, Heracleum, Prunus, Pyrus, Rhamnus, Rhus, Ribes, Rubus, Salix, Spiraea, Vaccinium, Viburnum, and Zizia. The geographic range of the species extends from Nova Scotia west to Minnesota and south to Georgia. It is active from March to July.
In early spring as the soil warms, males emerge and swarm over the colony, waiting for females to emerge from their underground nests. They mate, sometimes in midair and sometimes rolling on the ground! The males feed on nectar for a short time after mating and soon die. Females build a new nest in the ground, a 1.5 foot deep straight-down tunnel about the width of a pencil. Eggs are laid individually in cells along the edge of the tunnel. Each night, the female creates a new cell and lines it with ‘polyester’ a plastic-like substance that keeps the cell dry and protects it from fungi and bacteria. The material is produced from a gland on her abdomen and she spreads it over the interior walls of the cell using a short forked proboscis. A liquid mixture of nectar and pollen is placed in the cell and the egg is laid on the wall just above the liquid. Once the egg is placed, another plastic-like substance called linalool is produced from a gland near the mouthparts and spread over the egg for additional protection. The new generation will remain in the ground until the following spring.
The plastic produced by these ‘plasterer bees’ is biodegradable and some scientists are studying its characteristics with the hope of creating biodegradable plastics for commercial use.