Board Thread:Warhammer 40k General Discussion/@comment-25618639-20150406151006/@comment-6078851-20150408161137

i'm not sure that tyranids would utelise the orkoid form of reproduction: when an orc dies it releases a lot of spores, but from those many, many spores, there may only be a dozen cocoons. plus the gestation time, while super fast compared to other species, is very slow compared to tyranid reproduction - ork spores take a couple of weeks to gestate i think (i havn't read anything that states explicitly how long they gestate for, but between 1 to 3 weeks is what i infer), while brand-new tyranid bioforms can be created mere hours after recieving the genetic material.

orkoid reproduction is probably the most efficient form of reproduction amongst the milky way's native life, but tyranids aren't native and the efficiency of orkoid reproduction pales in comparison to tyranid reproduction.

but then maybe tyranids, the undisputed masters of biological engineering, are working on improving the efficiency of orkoid reproduction, and we may yet see a tyranid invasion being heralded by a planet being 'cropdusted' with orkoid spores which grow and birth tyranids in a matter of hours, and instead of growing a dozen or so cocoons from thousands of spores... thousands of cocoons will grow from thousands of spores :)