Damselfly for ID

[RoyW]

Originally Posted by Dogghound

Without doubt Ischnura elegans f.infuscans-obsoleta the adult form of rufescens.

Now usually referred to as f. rufescens-obsoleta, although I don't understand the reason for the change, or why it was considered necessary (I always assumed that when rufescens-obsoleta was given as the name it was a mistake based on the fact that it is the colour form that f. rufecens matures to.

Originally Posted by htcdude

Without being a pain can I ask what rules out female Emerald?

Originally Posted by Dogghound

1. The resting position with the wings closed. Lestes tends to almost always rest with the wings open spread out (although some tenerals dont do this as often).
2. The pterostigma (Little black square in the top corner of the forewing) is two toned typical of Ischnura . Lestes have plain pterostigma which are longer.
3. Female Lestes have an almost split abdoment tip due to the ovipositor sheath. Here it is a blunt end with a vulvar scale.
4. The colour female L.sponsa are a washed out cream on the flanks and underside, this is quite yellow. It lacks and metallic green typical of Lestes.
5. The thorax lacks a broad metallic humeral stripe (suture). Lestes tends to have quite an extensive area of metallic green on the thorax, even when I.elegans has a humeral stripe its not as broad as Lestes.
6. The structure in comparsion to Ischnura, Lestes is very delicate with a long thin abdomen.

I hope this helps, if you get several images up you should see the differences, its not always easy with Ischnura as it has a variety of colour morphs.

Generally a very good description of some of the key features from Dogghound - who hopefully won't mind me "picking on" the points made (and possibly complicating things a bit - sorry!)

1. Even fully mature Lestes will often close their wings over their abdomen, especially in cool conditions. They will almost always have their wings half open when they first land, but may close them before you get into position and focussed for a photograph (so the wing position is useful in the field, but not always useful when identifying someone elses photo).
2. The pterostigma frequently has obvious pale bands at the sides in the commoner two Lestes in the UK, and is very obviously two toned in Lestes barbarus, Southern Emerald Damselfly/Migrant Spreadwing, which is now regular, but rare, in the south-east (so needs to be taken into account). In all Lestes the pterostigma is much more rectanguar in shape though.
3. The apparently "split" abdomen tip in female Lestes is due to the ovipositor being far larger (the ovipositor sheath is actually relatively small). If PurplePixii's photo was more from the side the ovpositor could also be seen clearly on this Ischnura - though it would be far more obvious on a Lestes.
4. Immature Lestes can be very yellow (even orange) underneath, and when very mature can turn bronze -lacking any green (athough still 'metallic' looking).
6. Female Lestes (especially Lestes dryas) are far more 'heavy' bodied than Ischnura species.


Most damselflies can be very variable, so they can be difficult to identify at first - we don't have too many to consider in the UK though (although the number is increasing), so it is possible to get used to the variation!