Hi Cath, this looks to be an Iridomyrmex, but I can't be sure which - possibly Iridomyrmex niger. The published research by Peakalll & Beattie in 1989 (link to the paper below) suggests that the main ant pollinating this orchid is Iridomyrmex gracilis (now called I. bicknelli) but the ant in your photos doesn't look quite right. Great to see the photo with the pollen granule attached! Cheers, Jon https://www.jstor.org/stable/pdf/2389565.pdf?refreqid=excelsior%3Af44015e79b949370da7e08425c9a4e4c
Thanks for the reference, Jon. I have also seen Crematogaster with pollen on the same species of orchid (sighting 4354296). Ants are frequent visitors to Microtis flowers, and are thought to be attracted by nectar. It's possible that a number of different species could pick up pollinia as they feed and then carry them to other flowers.