A widespread Bluetail that is native in Australia (all states), Fiji, Indonesia (Maluku, Papua), Papua New Guinea and various Pacific islands. It is unfortunate that it is called the Common Bluetail, as is our own I. elegans in European circles. A good reason for being circumspect about common/vernacular names.
We found these a stones throw from our residence in Stanley, near Beechworth, Victoria and at Metung down on Victoria’s south coast. They were also widespread on my 2019 trip to Queensland.
Gender determination can be tricky – I messed up – with blue form females looking like males. The dorsal black mark on S2 seems the clearest determinant, being an arrowhead mark on females but flaring towards the thorax in males.