You’ve got one of our 4 Emerald Damselflies [ unless you have only the 3rd ever record of a Winter Damselfly in the UK 🙂 ].
2 of the UK’s Emerald Damselflies are generally quite distinctive (but note the warning which follows) and these features are gender-neutral:
Warning: There is some potential for confusion with regard to the Willow Emerald Damselfly thorn shape – Scarce Emerald Damselflies can also occasionally show a pronounced thorn BUT they do not also show a clear antehumeral stripe:
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A pronounced thorn but this is a female Lestes dryas
Neither of the above? The remaining 2 Emerald Damselflies require a bit more work.
Are we dealing with a female or a male?