Very large wasp.

Yesterday I saw a tree full of holes with two young Yellowbellied Sapsuckers in that tree. There were a couple of Hummingbirds that were sneaking in there to drink from the sap holes. Every time the Hummingbirds came by the Sapsuckers would chase them away. Then I noticed some flying critters that were smaller than the hummingbirds, It turns out that they were giant wasps, each about an inch and a half or two inches in size. But when the wasps would show up the birds would not go near them. It was an interesting game of paper scissor rock between the three creatures, With the wasps being the untouchables.

This wasp is called a Cicada Killer.

http://www2.ca.uky.edu/entomology/entfacts/ef004.asp

http://en.wikipedia.org/wiki/Sphecius_speciosus