It pisses me off how simplistic Shinichi is compared to Migi. I do understand that if Shinichi was the ultimate partner right from the start this show would be rather boring. While it's necessary, it's still frustrating to watch. The teacher seems more tolerant than I am at least. Then again, humans being illogical is an interesting point for her as well.

Quote Originally Posted by MFauli
Also, I wonder if being pregnant limits her abilities. Afterall, splitting up your body seemingly randomly cannot be good for a "normal baby".
Only the core can transform. For Shinichi that means his right hand. For the rest of them it means their head. The body is relatively intact from the neck downwards.

These are parasites, not viruses. The latter put self-replication above all else, including the destruction of the host. The former's success lies in living with the host for as long as possible. The lack of desire to self-replicate indeed makes them different from most animal species from our planet. Ants and such insects have worker subtypes, but these parasytes don't appear to be hive-minded either. There is no inherent structure to their way of life at all.