Robberfly - Asilidae - 
Cerotainiops abdominalis.
 Otero Mesa (4960'), Otero County, New Mexico
This is the most colorful robberfly I have seen.  It is very small (10 mm) and the prey is a Harvester Ant (Pogonomyrmex)
This from Dr. Eric Fisher:  These are nice photos of Cerotainiops abdominalis. This is one of the few asilids documented to feed on ants. (These guys like to sit at the edges of the harvester ant clearings and pick off individual Pogos.)

Dorsal and Lateral views - July 28, 2009

Habitat - Grassland/Scrub with rocky limestone soiil
images copyright Bob Barber