Easily told apart from the other chasers with both sexes having a very broad flattened abdomen which gives it a swollen (broad/fat) appearance. Males initially emerge with the same colourings as females but their abdomen will gradually develop a sky blue “pruinescence” which is not a pigment colour but a waxy bloom. The abdomen is broad and flattened with yellow spots on the side. Both wings have dark patches which can also help in identification.
The immature male resembles an adult female in colour with an olive-yellow abdomen bordered by yellow markings.