You are outside when you notice dozens of what look like bees milling about around a sunny area of your yard. When you look more closely, you find you see they are about 1/2 inch long and black. Many of them don't seem to be going anywhere but every once in a while, you see one land on the ground and crawl into a burrow. However, different individuals go into different burrows. Even though they look like bees, you don't get stung despite being really close to them.
1. What are these insects?
This is a type of solitary bee known as an andrenid bee. Unlike social bees, like honey bees, that have live as a colony with different castes in one site, solitary bees live on their own in separate nests. In the case of andrenid bees, they are gregarious, i.e. many of them will make nests near each other. They prefer to nest in sunny spots in areas of thin grass or sparse vegetation. They are commonly found in lawns, especially on slopes that face south, and in gardens.
2. How long will they be present?
These andrenid bees are relatively short-lived, not surviving for much more than a month. They overwinter as pupae and emerge as adults in spring. They spend much of their time finding pollen to provision their nests for their young which will hatch later. When she is done, the andrenid bee will close off the nest with mud and then die soon afterwards.
3. Do they sting?
They have stingers but rarely use them. They are very docile and very rarely sting people.
4. What is the best treatment?
If they are not bothering you, just leave them alone and allow them to go away on their own. You can try to discourage them by keeping the area watered -- they may leave to seek drier sites. As a last resort, you can pour soapy water into burrows. However, remember that the risk of stings is very low and they are present for just a short time. Andrenid bees are beneficial because they are pollinators.
