We have a ranch house in a suburb of Chicago. In the back, there's a set of three concrete steps which lead from a sliding glass door to the "patio" which is simply a concrete slab. Beyond the slab is a large hedge, and to one side is our vegetable garden.
There is a small opening about 3/4" high by 4" long where the concrete stairs meet the concrete slab. Some flying insects seem to have taken up residence in the space under the steps, entering and leaving via the small opening (doorway?).
These little guys are about 1" to 1-1/4 long. They appear to have black segmented bodies like ants (but I'm not sure). Their wings seem to be opaque and have a blue sheen. When they're at rest, one wing folds over the other and the folded wings lie on top of the body. The wings are about the same length as the bodies.
These insects fly rapidly in arcs, landing once in a while on the steps for a few moments, and occasionally visiting the large shrub. They often seem to fly in pairs, circling each other.
One day my wife was watering the veggie garden and squirted a stream at the "doorway". Three or 4 of the insects appeared and began to buzz her. She felt they were acting aggressively, and she wisely backed off.
Does anyone have any idea (1) what these insects might be, (2) are they dangerous (stingers?), and (3) what can be done about them?
If more information is needed, please post here or email (but remove the "nospam" from the address).
Any ideas, comments, or suggestions will be gratefully received.
-Len