I'm not exactly sure how X parasites reproduce inside their hosts, all I know is that it's asexually. They could reproduce like a starfish, breaking off a limb that will grow into a clone of it's original while the original regrows the limb. Or perhaps they just drop an egg or some other biological matter that eventually grows into a clone. It could be that they just split down the center like Ash in Army of Darkness. Or maybe it just uses the host's own method of reproduction by impregnating itself. It might not work as well for a male host, but supposedly even men have the ability to carry children... but that's a whole other can of worms. Either way, I always assumed that whatever method the X use, it does leave them temporarily vulnerable if only for a few minutes. That might not seem like such a bad thing, but the X-Queen is planning to dispose of them anyway.
i always thought they divided like giant cells, maybe they temporarily go blob.
I thought they might reproduce like viruses or at least in a manner that harms the host's own cells
perhaps they fuse their dna with the cells.