Wasp,

OK,, Now this is a good read, but also remember wasp are beneficial, so before you eradicate answer some simple questions. do they pose an imminent threat to live stock or family? are they in a dangerous place? Also are they a species that can be overly aggressive?

Wasp prey upon worms, spiders and other pest. If you run across a hive or nest make sure before you kill them can they be a benefit first?

http://eartheasy.com/live_natwasp_control.htm