Hi Natureguy, these ants do look a bit like Iridomyrmex, but there are a couple of things that are a good guide towards Monomorium. Firstly, your ants are very shiny, and there are very few Iridomyrmex that are so glossy looking. Second, you can just see in your photos the structure of the ant between the main body and the tail (gaster) and this is a very important diagnostic feature for all ants. Between the main body and the gaster, ants can either have one small segment (a petiole) or they can have two small segments (a petiole and a post-petiole). Iridomyrmex belong to a sub-family of ants known as the Dolichoderinae, and they have only one segment between the body and the tail. Monomorium belong to the sub-family Myrmicinae, and they have two segments. You can just see the two segments, small bumps between the body and gaster in your photos. Cheers, Jon