Board Thread:Warhammer 40k General Discussion/@comment-25618639-20150406151006/@comment-6078851-20150411151218

you're missing the point about an improved spore reproduction: genestealers have to work covertly because their numbers are so few, and have to slowly convert and breed to build up their strength. if a world were 'cropdusted' by a bioship using improved orkoid-type spores then in a few hours there would be an entire army of tyranids on the surface, and any pdf force would be caught utterly unawares as there would be no word of unsavoury cults nor people going missing.

genestealers are used primarily as scouts for hive fleets, and to draw them towards concentrations of biomass, but if such scouts had a spore-bioform amongst them it could save tyranids a lot of unecessary effort required in planetary consumption - look at the hassle regular ork spores cause to planets, even high-tech and well armed worlds - they are almost impossible to get rid of once started, and that's with gestation of a couple of weeks and only a dozen or so cocoons per-thousands of spores.

and yes, there would be squigs. squigs are not tyranid in nature, although they seem to have tyranid dna they're still orkoid as they are a fundamental cog within the orkoid self-sustaining ecosystem.