The Skrit Na are a race of scavenger aliens with two rather distinctive lifephrases separated by a naturally occuring metamorphosis.
The Skrit Na are unusual in that they appear to look like two different races, but they are really the same species with two life phases. The first is the Skrit, a dim-witted cockroach-like creature that's almost as big as an Andalite with fourteen legs and six sets of antennae. The Skrit then forms into a cocoon, and emerges a year later as a Na, which look exactly like the famous "Grey Aliens" from popular culture. They have grey skin, large heads with two huge eyes, and 2 very slender legs. They seem to get smaller when they metamorphsies, since Skrit are described as the size of Andalites, as the Na seem to be more human sized.
The Skrit Na are notorious for abducting species' from different planets to either experiment on them, or put them in a sort of alien zoo back on their homeworld. Their spacecrafts are shaped like flying-saucers.
The Skrit Na are neutral in most intergalactic matters especially the Andalite-Yeerk War. They are unsuitable to become Controllers, but the Yeerks often strike deals with them in order to acquire new alien technology. However, the Skrit Na do not belong to the Yeerks, nor are they allies of the Andalites.
A large number of Skrit Na were reported to have been absorbed by the being Father.