1.Build spies. Lots of spies. Great galloping gobs of spies. In the bottom is good for being counter spies. Research some of the spy bonus techs or trade for them.
2.Demand that the gibbering monstrosities stop spying. As the charasmatic humies there's a good chance they'll stop esp. if you have a fleet to back your demands up.
3. Nuke the $*&5ing Darlocks till they glow.