What if swarm of ants is a metamind? It is obvious that single ant is a being but what if swarm of ants is another kind of being?
Do you have ideas how we could communicate with it?
Good question, and no one really has a definitive answer, but it is generally considered that a system, as you described, is not a metamind as you call it, or a singular being.

First lets define what a being is:

A being is a system that works together to collectively maintain all characteristics of life. These are:


being made up of cells
the ability to reproduce
the ability to react to a stimulus
Organization 
Metabolism 
Growth
adaptation


A swarm of ants contains all of these characteristics, so it could be classified as a 'being'.

Though the problem is that the reactions and actions taken by a swarm of ants is not considered as adaptable or as self sufficient as a single being. For example colonies of ants are able to effectively create short paths, though this is due to the physiological structure of the ant colony itself, and not its intelligence. Artificial ant networks are based off this structure, is this simulation a metamind too?

Another scenario to consider is if you placed an ant colony in a particular unknown situation. Would the ant colony be able to fight off predators, look for food and other life related characteristics? Ant colonies do not particularly work in this fashion.

This problem casts doubts as to whether an ant colony is a metamind. 

On the other side of the coin though, the mind body problem has not been resolved and therefore there is no definitive answer to your question. For example monism states that consciousness is singular.  

Overall though a swarm of ants is not considered a 'being' or a metamind in contemporary psychology.