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Knowing your damselflies - an apology and a quick ID guide

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Paul Deane Paul Deane | 17:42 UK time, Tuesday, 5 June 2012

Q - How do you tell the difference between an azure and a common blue damselfly?
A - Well we didn't get it right...

In last night's programme we ran a Jubilee-themed quiz where we asked you to identify three species that were partly distorted under a Union Jack flag. The theme was 'Red, White and Blue' and we had thought we'd picked a redstart, a white-tailed fish eagle, and a common blue damselfly.

As was pointed out by SeanGraham25, Colin Law, pen-y-bont_mike, Elaine Rice, Dave Smallshire, Huddsbirder and others, we made a mistake!

The picture that we posted was actually an azure damselfly, not a common blue damselfly.

So we've put together a quick ID guide so that next time you're out damselfly spotting, you hopefully won't make the same mistake as us!

Common and azure damselfly ID guide

Common and azure damselfly ID guide

Picture credits:
Azure damselfly by Martin Webber

Common blue damselfly by snapp3r

Thanks again to those keen eyes out there who spotted this.

Comments

  • Comment number 1.

    Personally I don't find the anti-humeral stripes particularly useful as an ID feature unless you are looking at a good image or a specimen you are holding with a magnifier because they are so hard to see. I think with the males at least most people use the markings on segment 2, and even these can be difficult to see without close focusing binoculars. Plus of course these are only the males.

  • Comment number 2.

    I agree with theSteB that the flat bottomed U marking on S(egment)2 of the Azure and its absence on the Common blue is by far the easiest way to separate these two species. It's why, despite being quite certain, I waited to see the full photo before giving a firm ID on the quiz blog.

    I could try to explain from your photos but it's easier to use others. There are better photos but I am using mine because I can add notes and link here. Photos 1 and 2 have a note showing the location of S2. Hovering the mouse over the photo will show the note. Clicking on the photos will provide a better view and selecting "View all sizes" will enable you to see the photos at their largest size.

    Photo 1 - Male Azure

    http://www.flickr.com/photos/pen-y-bont_mike/5787244415/

    Photo 2 - Male Common blue

    http://www.flickr.com/photos/pen-y-bont_mike/5794765902/

    Photo 3 Male and (most of) female Azure in mating wheel

    http://www.flickr.com/photos/pen-y-bont_mike/5797617418/

    Females of all species are notoriously difficult. They usually have fewer distinguishing markings and often come in several colour forms. The photo above shows the green form of the Azure which I believe is the most common for this species.

  • Comment number 3.

    Just one quick note with this. Some of these damselflies of the family Coenagrionidae are quite variable, and I believe some are impossible to separate by appearance. I found this out the other year when I corresponded with a professional entomologist working with dragonflies. I sent him a photo someone has asked an ID on, because I wasn't sure and superficially it appear to be a rare and significant species. He sent it to someone even more expert. The opinion was that it as probably an unusual variant of a more common species, but they couldn't be 100% sure. I learned that even the experts have to use molecular markers in lab analysis to be sure of some species. Usually the problem is the females which are far more variable, with some of them developing a male colour scheme.

 

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