Eastern Yellowjacket

Its a vespid wasp--- most likely a "yellow jacket".

The antenna lead me to believe that this is a wasp or bee of some kind (not a fly) and the lack of hair rules out bees? This is the source I usually use to identify insects http://www.pbase.com/markb249/iowa_leps and from here I think it's an Eastern yellowjacket (Vespula maculifrons).

Though in this case, the reference (below) doesn't appear to have it!

Here is a reference you can start with for your spottings: http://www.insectsofiowa.com/