In regards to attaching a parasite, E3 says:
Host Suitability. Place the new Parasite to the left of its Host’s card. The Host must be in the tableau of another player in the home row ( E2 ) of one of your Organisms or in an active row.
I interpret the above as: The Host must be in the the tableau of another player and the Host (or Host's Host if a Hyperparasite) must have a landform icon that is either the same as that of one of your organisms, or that of an active row.
Is that correct?