Dragonfly ID please, Switzerland

[LancsRover]

Hi all, can anyone ID this dragonfly please, I saw it in the Locarno area of Switzerland a few days ago. It looks like a broad-bodied chaser but it is about half the size. My best guess(from my book) is a KEELED skimmer, but in the mating photo's both "flies" are blue and the female(mature) should be brown??
Cheers Russ

[Mikhail]

The pale bluish face points to Southern Skimmer Orthetrum brunneum, rather than Keeled Skimmer.

M>

[bugboy]

I'd go with Southern Skimmer as well, although Keeled Skimmer males in southern Europe have bluer thoraxes than those in the UK apparently.

[LancsRover]

Thanks Mike and Bugsy, mine was only a guess
Russ

[Johncob]

Russ I havent seen one of these in the UK as you guessed. However more learned people seem to have got the ID sorted. Regards John.

[Sylvie_h]

Hi Russ,

I think all specimens are Keeled Skimmers (Orthetrum Coerulescens) for the following reasons:
I can see that the radial supplemental vein (rspl) on the wings subtends a single row of cells whereas Southern Skimmer’s has a double row of cells. Also the behaviour tells me that they are keeled skimmers. In my experience, I have never ever seen O. Brunneum perching on vegetation but always on the ground and very often on bare stones near water, even in the wheel position, they tend to stay on the ground. The pterostigmas are also very large in O.Coerulescens and tend to be more yellowish than O.Brunneum (although the colour is not always a reliable feature for identification).
The other indication is that O.Brunneum is normally of a uniform light blue on thorax and abdomen and has a bulkier body whereas the Keeled Skimmers are normally more pruinose especially on the thorax and have a thinner abdomen.
It is a very tricky one I have to admit as both species can be very similar. It takes a while to get used to it and with experience these little differences become easier to see in the field.
Here’s a picture of the Keeled Skimmer taken in Bulgaria.
Sylvie

Keeled Skimmer

[Mikhail]

Sylvie
I bow to your superior expertise in Odonata. but one thing bothers me. In my field guide (Dijkstra and Lewington) it is stated that in brunneum the face of the adult male is whitish with a blue hue as opposed to dirty pale brown in caerulescens. This is why I opted for brunneum in this instance.
M.

[Catteraxe]

Hi Mikhail

An interesting point about the face colouring in the Dijkstra/Lewington field guide. I have the Brooks/Lewington Dragonflies and Damselflies of Gt. Britain and Ireland which shows the Keeled Skimmer with a bluish face. If nothing else it shows how the field guides themselves differ!

Kevin.

[Sylvie_h]

Hi Mikhael,

You've made an interesting comment. Personally I don't think this is a 100% reliable feature as there is very little difference in the coulour of the face in the South of its range. The only way to differentiate both species is to look at the wings and the behaviour. O. Coerulescens is a difficult species not counting the subspecies, one of them being Anceps which can only be differentiated looking at the apex as far as I know... A real headache!
Sylvie

[LancsRover]

Thanks to John, Sylvie, Mike and Kevin for a very detailed ID and discussion, I'm a lot wiser now
Cheers Russ.

[Chris Jackson]

... I'm a lot wiser now ...

You're not the only one, Russ. So much to learn .......
Keep up the sightings.
Chris