The Xenomorph incorporates each new species it assimilates into the next generation of Xenomorph. Do all of the different variations of Alien Xenomorph Queens lay the same basic facehugger egg, or is each generations egg dependant on the species before it? Simply put, do the eggs evolve along with each Xenomorph version or is it a one egg laid by all scenerio?
The incorporation happens on a genetic level, which is also why it is only a partial change as the Alien DNA remains dominant. The new species host is only somewhat assimilated, and it does not change the method of reproduction, which is again deeply genetic. The fact that the Alien is fundamentally an egg-layer with intensely dominant genes means it will always remain an egg-layer. The face-hugger is sort of the embryonic / larval stage of growth prior to major differentiation, so the host's features do not show up until after this stage. Hence, once a face-hugging egg-layer, always a face-hugging egg-layer.