Wedge-shaped Beetle
Ripiphorus vierecki
Photographed in Estes Canyon, Ajo Mountains, Organ Pipe Cactus National Monument, Arizona, USA. May 2013. Length is about 6mm.
Ripiphoridae -- Wedge-shaped Beetle Family
Wedge-shaped Beetles don't appear to be beetles at all with their very small elytra, large transparent wings and bee-like color patterns. Notice the large, feathery antennae.
From Wikipedia: Ripiphorus attack bees by laying their eggs on flowers, where they hatch almost immediately into small planidium larvae that wait for a passing host. They grab onto a bee when it visits the flower, and ride it back to its nest, where they disembark and enter a cell with a host larva. The beetle larva then enters the body of the host larva, where it waits while the larva grows. When the host pupates, the beetle larva migrates to the outside of its body and begins to feed, eventually consuming it.