UPDATE: Based on some unscientific web-surfing research, I’m pretty sure this is a Hummingbird Clearwing Moth! Here is some info and a few pictures.
Whatever this thing is, it’s huge! Maybe the size of a small hummingbird or large butterfly. It’s huge, scary, but fascinating! I’m guessing it’s some kind of moth. It has the markings of a bee, but way too large. I asked my Mom to take these pictures, which she happily did…until it CHARGED at her! He, he, he…funny now!
Here is a close up of the back. It was about 6pm at Lake Katherine of Palos Heights, IL, when this picture was taken, I don’t know if that helps any. If any smart person out there in cyberspace can share some knowledge…I would be very thankful!
Thank you!
Let's Paint Nature! 
Whoa! That is big. Is it some kind of dragonfly? I know they can get really big.
Drowsey: Big and scary! Hummingbird Clearwing Moth is what I think. Run for your life if it comes after you…he,he,heee…..
You’ve got it right. It appears to be a clearwing hummingbird moth. I’m insanely jealous!
Wow…never heard of one of those before!
I was just visiting another site and they were talking about a robber fly….here’s the link. Never heard of that before either! Hope I don’t run into these creatures! lol
http://www.mistyswords.com/2008/09/camera-critters-22.html
Tell your mom she got some awesome shots! I’m major jealous too, because I’ve been wanting to see one of these in person!!!