The aliens are mindless creatures. They act on instinct and are not really all that smart. Think of xenomorph as a worker ant. It has an objective to gather food for storage and such... It just does what it is supposed to do. Every xenomorph has an objective. The "face hugger" has to seek out a host to desposit the alien/egg/whatever down the throat. The "chest burster" escapes from the host, killing the host in the process and must grow into a full fledged xenomorph. So, the fully grown xenomorph works for the hive and defends the hive with it's life all while collecting hosts for the eggs to help the hive grow strong with more xenomorphs. Now, there are two theories I heard about the queen of the hive. First off, the queen of the hive must keep reproducing eggs. Let's just get that out of the way first. I've heard two theories about how alien queens come to be. The first one is mentioned in Alien 3. It all starts with a face hugger... There is a special face hugger called the "queen face hugger." It's much larger than the normal "face huggers" and instead of that tan color, it's black. One of these face huggers put the alien queen in Ripley's stomach. If you watched the deleted scenes in the Alien Quadrilogy, one of the convicts finds the "queen face hugger." The second theory about the birth of a queen alien is that the aliens have some kind of psychic energy. And, during the the start of a new hive... One of the aliens will evolve into a alien queen. However, if there is an alien queen... We will not see another queen in the same hive unless the hive grows too large for one queen to handle. So, yeah... But, what came first? The alien queen or the egg? We don't know. >_>; Also, another fact about the aliens is that... They take on characteristics of their hosts they are born from. Notice how the xenomorph sort of resembles a human in the first two movies and then the one that is born through the dog or ox in the third movie is much faster and runs on all fours a lot. Anyway, I'm done ranting about the aliens. I hope they win. But, I think the predators will win. Oh well.