Example on how to create swarms of flies.  Might be a little outdated since this page was written in 1998.  I don’t know enough UnrealScript at this point to comment on whether or not this code works.  I haven’t tried it yet either.

http://www.celticwarriors.net/Website/Mirrors/CHiMERiC/Tutorials02/Tut21/UnrealScript%20Tutorial%2021%20-%20Horse%20Fly%20Swarm%20Tutorial.htm