Board Thread:Warhammer 40k General Discussion/@comment-7186329-20130329201743/@comment-7232811-20130403212158

The Tyranids could not be influenced by a Chaos God, for two reasons:

1: They have the Hive Mind, which cannot (as far as we know) be corrupted, & protects even the more sentient Tyranid creatures from the taint of Chaos.

2: Chaos only really affects sentient minds, (psychologically that is) & as no Tyranid organism is sentient, they could not be psychically controlled or corrupted in any way shape or form.

Furthermore, the Hive Mind is not a 'blank' in the warp, like a pariah, but casts a shadow across it, effectively blotting out psychic activity. In this case, it'll be the psyker who'll be burnt through by it, not the other way around.

Not that the Hive Mind will save the Tyranids from getting butchered when they go into the Eye (Daemons, CSM, etc, etc).