Mind Worms can appear suddenly, and are closely associated with fungus.
Mind Worms and other alien creatures can engage in Psi Combat, in which weapon and armor strengths are ignored, and the attacker is given a 3 to 2 advantage on land. Morale level is quite important in defending against Mind Worms and other alien units.
With proper breeding and bonding techniques, Mind Worms can also be bred in captivity and controlled by skilled brood trainers. These Mind Worm boils can be used to attack enemy units using Psi Combat, thus bypassing enemy advantages in weapon and armor technology.
Biology Labs and other facilities can increase the strength of captivity-bred Mind Worm boils. Like any native unit, players can also release Mind Worms into the wild, to harass and disrupt an enemy.