Argentine or not?

Argentine or not?

Observation - Argentine or not? - Southern Africa. Description: I spotted ants in the front garden that looked identical to the Argentine ants I have recently photographed and posted - see here: http://www.ispotnature.org/node/789193. However, amongst them were ants with a gaster that had a different colouration - spe

I spotted ants in the front garden that looked identical to the Argentine ants I have recently photographed and posted - see here: http://www.ispotnature.org/node/789193. However, amongst them were ants with a gaster that had a different colouration - specifically some lighter bands were present. I went back to double check and these ants with the lighter gaster are not present amongst the other group of Argentines in my back garden. Is this just a colouration difference or a different species. They look so similar otherwise that I favour the former. Note some kind of phoretic mite on the side of the gaster of the individual I ended up photographing. Perhaps I will try to photograph some more individuals to see how representative this colouration is. Size approx. 2.5mm.

Edit 1: Added one more pic of another Argentine with swollen gaster leading to this sort of colouration.