From your photos the insects look like mining bees.We have had many reports of mining bees this spring. They are beneficial pollinators and control should be avoided if possible. They are solitary bees and do not sting. Their activity is usually brief about several weeks. They like exposed soil and good drainage. In flower beds, you may want to lay landscape fabric down and cover with several inches of mulch to discourage them. In lawn areas, seed in the fall to thicken up your stand of turf. See our website for more information http://extension.umd.edu/learn/mining-bees   

mh