Scale the tower of Southwind Village and locate a means to stir the silithid hive into activity. Bring back anything unusual you may uncover when doing so to Layo Starstrike at the Valor's Rest graveyard of Silithus.
The hive needs to be addressed in Southwind Village, and I think I know a way to get at them. It's been my experience that the silithid hives are very sensitive to their environment; this explains their attacks when hearing the death wails of the spirits.
The silithid are strongest in the tower - the one with the mass of wasps circling it. Scale the tower and jostle the hive into activity. Report back what you learn, but be careful! If you uncover anything that might help, bring it to me.