Behavior
Robber flies, also called assassin flies, from family Asilidae are powerfully built, bristly flies with a short, stout proboscis enclosing the sharp, sucking hypopharynx. The name "robber flies" reflects their notoriously aggressive predatory habits; they feed mainly or exclusively on other insects and as a rule they wait in ambush and catch their prey in flight.References:
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http://bugguide.net/node/view/25570http://www.hr-rna.com/RNA/Rfly%20pages/Promachus%20page.htm
