Hmm I think i'll agree on your first option Dave, because if the second option is true, how can the Xenomorphs reproduce and over populate its prey? And another thing if the Xenomorphs that are guarding the queen, or even the queen itself when she is in a ovipositor, they dont eat much because I dont think many can even survive going through all the others until they have reached the queen herself; so if food and energy is paramount they'll die really quickly don't you think? What I think is that they carry some metabolistic impending chemical from the egg spore stage which gives energy into the blood and tissues of the Xenomorph that regenerates and feeds the Xenomorph with vital complex sugars to give it energy to atleast its minimum requirement.