I touched on the umwelt concept during some research I was doing for my Masters but didn't give much thought back then to how it would apply to colony organisms like ants. I still see organisms like that as having an individual umwelt however, as there is still sensory information they share among themselves regarding the location of resources etc. To my mind, the concept of a shared umwelt would imply each individual is at all times aware of all aspects of the colony which, of course, isn't the case. It's an interesting concept to play with though. There are so many questions in cognitive fields which are exceptionally difficult to realistically answer though. One thing I've always been fascinated by is episodic-like memory which is also exceptionally difficult to prove in animals - I.e. Separating out general associations with a particular object say from recall of a specific event involving that object. I wonder whether we'll ever find a way to address these types of questions?