Gallinipper Psorophora ciliata

The nickname 'gallinipper' perfectly captures this insect's defining trait: an unusually large size combined with notoriously aggressive behavior that makes it actively chase down victims. Its shaggy legs give it a distinctly different appearance from other mosquitoes—hence the 'shaggy-legged gallinipper' alias. Indigenous to North America east of the continental divide, it's one of thirteen Psorophora species found in the continental United States, but definitely the one most likely to pursue you with determined aggression.