Well, shadowatching, you're actually very close on that topic --
A xenomorph will morph (or molt, as we have seen shedded skin in the deleted scenes of Alien), but they won't eat their flesh for extra nutrients in the face of danger. That's why there was still skin lying around in Alien, but not in Aliens.
AVPunlimited, I've had enough of this. Quit spamming my topic, stop accusing me, and grow up. I wrote this biology a year ago, and it clearly states that xenomorphs eat in its text. I have stuck by that belief since I first wrote it.
Acid is not a source of energy. An acid will destabilize and eat through other substances. Acid itself makes no energy.