Board Thread:Warhammer 40k General Discussion/@comment-6589306-20130228113457/@comment-6078851-20140622145502

yeah, tyranids need biomass to increase their race but that's essentially just food. xeno's also need biomass (food) because despite how hardy they are they still starve to death if they don't eat. xeno's need food and a host to propogate whereas tyranids have no such limitation, tyranids only need food.

in regards to xeno castes there's technically only two - queen and drone. the drones are the warriors. when it comes to the runner, praetorian etc, they are all still drones/warriors - their forms are dictated by the host they are birthed from but they're still drones/warriors (although to be pedantically technical there's only one caste - xenomorph - because any drone can alter itself to mature into a queen, if a queen is needed).

when xeno's are on their own they are all superlative solitary hunters, but when the same xeno's are numerous they become the 'swarmers'.

there is indeed no hive mind in the xenomorphs but there is a central control in the form of the superqueen who controls all the queens. the thing is though that the superqueen is a physical entity and can be killed but the hive mind isn't even a corporeal entity, and therefore can't be killed with anything short of annihilating the entire race.

the tyranids can't be wiped out, and maybe xenomorphs are too pernicious to be wiped out also but, xeno's don't have spacefaring technology (or any technology) so they could be entirely contained upon a planet (or multiple planets as they have spread somewhat) like something similar to the megarachnid of murder. although if they were contained on a planet/s i don't know if they could survive - once they've used all the life on the planet capable of sustaining xeno embryo's then there's nothing left to host more xeno's. after which the only things that could host more xeno's would be the xeno's themselves. and amongst all the 'xeno lore' i've accrued over the years, something i still have no idea about is if xeno's are actually able to birth from xeno's.