The chestbursters differ because they borrow a degree of their hosts traits. A possible reason is so it may be better suited to handle the environment of said host, and/or to better compete with that host. I dont know what degree is borrowed from the host, but I've made the theory (I'm sure I didn't MAKE it, just made a board about it) that it is actually very little. I doubt the aliens would be gifted with flight, but its possible.
Drone, or warrier or w/e you wanna call em. The bony exterior is due to...well...it being bone.How do you know they communicate through screetching and growling? I can see instances of where this can be infered to a degree; however, it is also clear (mostly from A:R) that they communticate through a sort of ESP, or collective hive-mind. They are also very intelligent and able to solve problems very quickly, and have reasoning and understanding of other creatures, to some degree at least. I suppose its fair to say the hunt in packs, but the size seems to differ on the amount of people they are hunting, and how armed/powerful they are. They are very capable independent hunters aswell.
"Runners" or, rather, THE 'runner' was the way it was, in general opinion (I have my own, in the thread I mentioned before), because it was born of a four-;egged creature (an ox or dog, on if you take A3 or A3SE as canon, doesnt really matter either way). The 'runners' do, in fact, have the ability to spit acid, as per A3 when it killes whatever the dudes name was in the fan (its first kill). All aliens attack from high and dark places, so I don't think its appropriate to lable that trait to just the runner. id also estimate that the 'runners' are just as durable as the drones. It may be a special type of alien from the Queen Facehugger to protect the queen embryo, but this is just [one of my] theory[s.], otherwise the 'runner' is just another drone that happened to be born of another species (than human)
The PredAliens...Grey with Black spots? Scrunched head? Dreadlocks (oh God I hope not)? Mandiables, yes. How do you know what their exterior is like? Why would it differ from the regular drones? Why would the species change their behavior?
Queens, Idk if Id call them female, persay. I don't think the aliens have any sort of sex to them and dont know if she actually needs to be fertalized to produce eggs. However it is a possibility. Idk about a Predalien queen, but don't think it would look much different, maybe a bit bigger, but thats even pushin it (although, again, it is possible) and I dont think smarter. The aliens intelligence comes fromt he aliens, not the host.
I would think from what we've seen aliens have a sort of ESP and Hive collective mind, as I stated before; what one knows, they all know. The aliens have a one-track mind, and for all their brain power and reasoning skill, seem to only have one goal: expand the hive.
Origins...theres a thread where you can find all sorts of theories on that.
The aliens are a silicone based life form, silicon can be in structures where is has little to no reaction with acid (sorta like glass).
Doesn't have thumbs? The aliens in Alien and A3 had TWO. And the Aliens in the rest had one. Now since they all have different digit numbers, I just count every finger grouping as one digit making (A1&3- ponter/middle, ring/pinky; A2- middle/ring) the alien finger count- 4 (including a thumb-like finger, though much longer)