Article by Abigail Pedlow
Winter is a good time to sort out for once and for all (or at least until next year) those species that are a bit confusing during the summer, when there’s too much else to look at to be bothered getting the book out!
Two of our most common damselflies are the Common Blue and Azure Damselfly, and they do look very similar. But there are differences, both in appearance and in their ecology.
A pair of close-focusing binoculars is helpful if you don’t have a butterfly net to catch them in. Otherwise patience and an ability to creep up on them are required. Azures have the habit of moving around the stem they are roosting on as you approach – so all you can see is an eye on either side of the stem!
As you can see from the illustrations, the male Azure (on the right) has a black U-shaped mark, that isn’t joined to the line beneath, on the 2nd segment of the abdomen. Although the male Common Blues (on the left) vary they usually have a ‘lollipop’ mark, with the lollipop stick attached to the line beneath.
There are also other differences – the thoracic stripes are wider on Common Blue, and they have more blue on the end of the abdomen. If you really get your eye in you will notice that the two species are slightly different shades of blue. Azures are paler than Common Blue - but that is really difficult unless you have both to compare!
They have different behaviours as well – Common Blue males are territorial and aggressive, Azure males much more peaceful in large groups.
They often occur together but Common Blue is more likely to be found on larger, open waterbodies, and Azure in small garden ponds.