The most common Coelioxys in the East.  

The most common Coelioxys in the East.  

This is C. sayi.   

Now, C. sayi is a nest parasite (like all Coelioxys) and it likes to drop its eggs in the nest of what is usually the most common Leaf Cutter in the East Megachile mendica.  That said, these bees are so little studied that it would not be at all surprising to find that are also  dropping eggs in similar hosts such as M. brevis

These bees are well armored against the stings of the hunky leaf cutters, to the extent that putting a pin through them when preparing them can be a bit crunchy (Another cocktail fact from your favorite government program).  Pictures by Dejen Mengis whose experiences in the Bee Lab caused him to join the Peace Corp.