New species, that would be cool.
Well i'm not sure about that, the same behavior is also noticed with Myrmica rubra
and some Camponotus
species. The reason is hard to find out. Could be like you said, inter colony power. As you probably know Myrmica rubra
can have more queens in one colony (some Componotus
species to), could be that the workers are from another queen. In that case. But i believe you only have one queen so...
How many workers are killed this way ?