This images shows a Diptera insect fossil found in the Florissant Formation of Teller County, Colorado, USA. It dates to the Eocene Epoch of the Paleogene Period. Thanks to Kenny for the microscope image. Field of view on image is 4 mm.
Learn more about this order of insect here:
http://www.fossilmuseum.net/Fossil_Galleries/Insect_Galleries_by_Order/Diptera/Diptera.htm