Insects from the Green River formation can be difficult to ID down to a species, let alone a generic level. Often you are trying to compare a 2D fossil to 3D pictures of extant insects and all you can do is hope you are correct. Below is a specimen I purchased because of the good preservation, but also because it had been ID'ed as a Weevil already. I need to go through my own findings to confirm but I think I have found examples of this same kind of insect on my collecting trips.
I am still trying to find some good resources that list known insect genera from the Green River formation but they are hard to find or expensive to purchase. At this point I can only say that this fossil is of a member of the Superfamily Curculionidaea.
A low light shot of the fossil shows some nice details
A direct light shot shows the true color of the fossil better.
This fossil was found in the Parachute Creek shale member of the Green River formation, in Rio Blanco County, Colorado. The Green River formation is dated to the Eocene period, Lutetian stage (about 46 mya).
Check out an older post of mine where I discuss the geology of the Eocene lakes that once existed in SW Wyoming and NW Colorado.
In another one I posted some of my exceptional finds from Douglass Pass.