How to counter illithids in early game ?

[VedalkenBear]

Depending on what the opponent is using to screen his Illithids, massed missile fire scripted to 'fire at large creatures' can possibly break the Illithids. They do not have very good morale.

(Obviously, if he is using large creatures as a screen, this tactic is less effective.)

Also, there is a 'critical mass' of Illithids necessary to 'work'. I find it hard to believe that a rush of Illithids would be able to achieve that critical mass to work.