The comparison chart below shows the UK’s six “mosaic” hawkers and 2 “brown” hawkers, both male and female, side by side.
The term “mosaic” is really borrowed from America where “Mosaic Darners” refers to Aeshna species. As such, the Hairy Dragonfly/Hairy Hawker (Brachytron pratense) would be excluded and, indeed, does not feature under the mosaic umbrella in Dijkstra. He does say, though, ” … often confused with smaller Aeshna species”. It clearly bears a strong, potentially confusing similarity so I have it under my “mosaic” umbrella to attempt to clarify those species those whose abdomens (male’s, anyway) are a very similar pattern of black bodies covered by a ‘mosaic’ of blue spots.
Two other hawkers have brown-based bodies of varying intensity and look quite different, to me anyway – there’s not a spot in sight on a Norfolk Hawker which has been a target of the taxonomists and is no longer Aeshna isoceles but Caliashna isoceles, so, as well as having no spots it is no longer in the “mosaic” bucket anyway.
I’ve included the Emperor Dragonfly/Blue Emperor (Anax imperator) because I have had one instance of it being confused. Unfortunately,
Not having snagged a female Azure Hawker (Aeshna caerulea), I am indebted to Chris Upson for the image of a blue form female [there is another form with yellow spots].
I’ve used both sets of English language common names.
For the annotations to be more readable, click on the chart to open up a much larger version.