[quote=Tyki]
actually, every zerg unit is connected to the hive via a psionic network, allowing them to do things with psionics. they just adapted an organ that constantly sent out a psionic emp, dispelling psionic and mental energies
[/quote]

Zerg are linked through a Hive Mind, which is, in fact, a chemical system, not a psychic system. Much like ants, they communicate through a system of fast-working chemicals. For example, in Starcraft, Raynor is tasked with placing a special beacon in a trapped area that would draw the Zerg through method of 'special Zerg pheromones'.