There is a large swarm of bee-like insects flying near the grass. What are they? Are they harmful to children? Can they be moved?
Baltimore County Maryland
Most likely these are mining bees, or predatory wasps which hover above the grass, both of which are non-aggressive and beneficial. Yellow jackets are another possibility, but would be seen all going to the same hole repeatedly.
We would need more information to answer fully.
Mining bees are solitary nesters, though there can be many of them in one area. Because they are not part of a social hive, they are not aggressive and just go about their business and should be left alone. In fact, though the males sometimes dance around, they don't even have a stinger. The females reserve theirs for the insect prey that they lay on their egg for the feeding of their future progeny. Their activity does not last long.
Bees generally have furry looking bodies and have pollen sacks on their back legs. They are beneficial pollinators.
Another possibility is a wasp-like insect which is a predator of grubs that could be living beneath your grass. They would also hover around and also are beneficial and non-aggressive.
That said, if you have a yellow jacket nest, these are social nesters and can be aggressive and sting if bothered or in defense of the nest. You would see them all continually go back and forth to one hole or opening. These you could control with an insecticidal wasp spray, or hire a professional pest control company. Correct i.d. is important so that beneficial, non-aggressive species are preserved.
Take a look at our publications here:
Common Stinging Insects- including yellow-jackets: http://extension.umd.edu/sites/default/files/_images/programs/hgic/Publications/non_HGIC_FS/EB248.pd...