Hi I am new to the group, and this is my 1st post to it.

Are these wasps much larger then normal? If so the may be cicada killers.
Which come out every year about the same time, hang around a few weeks then
dissappear again. If this is indeed what you have, they are fasinating
creatures to watch. They kill the cicada with their sting, then fly them
back to their hole. They will drag them down, and lay their eggs inside the
dead bug, giving their young a tasty snack when they hatch.
While being very large, they can be pretty intimidating, but I have never
heard of anyone being stung by them before.
I have had swarms of them around me while cutting my lawn, with out a
problem. though I will admit I have broken into a sweat with a bunch of bees
that sometimes almost reach the size of humming birds flying about my face.
: )