jccurd's picture

Southern Skimmer suspect: On Appeal!

Observed: 11th September 2011 By: jccurdjccurd’s reputation in Invertebratesjccurd’s reputation in Invertebratesjccurd’s reputation in Invertebratesjccurd’s reputation in Invertebrates

I was checking any Black-tailed-Skimmer-alikes to see if they might be White-tailed Skimmers when this fellow cropped up. Another new possibility to me - it looks most like a Southern Skimmer that's been round the block a time or two.
The dark tip to the abdomen is a little worrying but I'm wondering if the blue gets worn? The pterostigma look darker than the book pictures, too.

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Peter Allen's picture

Blue thorax

I think that the blue thorax also points to O. brunneum; the only other similar is O. nitidinerve which does not, I think, occur in France, or the southern form of O. coerulescens which does not have a blue face as the one in your photograph does. The blue pruinescence certainly does get worn in older individuals.

Hampshire Dragonfly recorder
Hampshire & IOW Wildlfe Trust

jccurd's picture

Thanks for that

Thanks, Peter. That's pretty much what I hoped/suspected from Dijkstra/Lewington. The blue thorax and frons particularly seemed a strong pointer together with location.


jccurd's picture

Suspect Cleared!

OK, I've been reading the Dijkstra/Lewington text more closely concerning O. brunneum.

Since there is no illustration of an immature male and swayed by the clearly blue thorax and, particularly, the frons, I'd wondered if some underlying black had been revealed on the abdomen by the wearing the pruinosity.

In the book's text, I now see that, "when not pruinose, the abdomen is uniformly brown" so bang goes my wearing off idea. :))

So, blue frons or not (do they go pruinose, I wonder?) O. cancellatum it is, then. Drat!

Now to take one off my new species list ...


PS, thanks both for your inputs, as usual.

RoyW's picture

"When not pruinose the abdomen is uniformly brown"

Unfortunately its not always as simple as looking for the underlying colour of the abdomen before pruinosity develops. Libellula fulva males develop prunosity over a largely orange abdomen, but where the blue colouring has been rubbed off in older individuals the colour underneath is black!
In my experience O. cancellatum often tends to have the immature pattern visible under the blue - and they can become pruinose on the thorax.

jccurd's picture

How about the frons?

I'm happy that this is O. cancellatum but I'm curious about this one having a quite blue frons. Is that just an ageing colour change or pruinosity (which is a deposited coating, right)?

RoyW's picture

Within limits of variation

Although Black-tailed Skimmers do not usually show this extent of blue pruinescence, I do not think that this one is exceptional - and this includes the blue colour of the frons.

Compare with these examples:

(scroll down on the second link).

The colour of the frons can seemingly be very variable on this species (white, bluish, or brown in mature males). Frons colour is of more use when trying to separate Southern and Keeled Skimmers, as the colour does not seem to vary much in these two species.
Pruinosity is a deposited coating, and I would imagine that it does affect the colour of the frons, particularly in older individuals where the pruinescence seems to spread.

jccurd's picture


Thanks for all the detail and links, Roy. Do you have all these relevant links at your fingertips or do you go looking? Either way, I appreciate your effort.


jccurd's picture

On Appeal

New evidence has been pointed out in the intriguing Southern Darter case. According to Dijkstra/Lewington, in Southern Darters "the Rspl subtends a double row of cells". The book shows 6-7 cells doubled. Unfortunately, it's not entirely clear to me exactly what constitutes the Rspl. If I'm seeing it correctly, this example appears to have 4 cells doubled.

The number of doubled cells appears to be mentioned to distinguish O. brunneum from O. coerulescens. What about O. cancellatum, though, for whom the book shows no such doubled cells? Hmmmm!

RoyW's picture

Doubled cells.

The Skimmer in this observation does have four doubled cells above the rspl vein, but this is no help with the ID (it doesn't even conclusively rule out coerulescens which can have up to four doublings, although this is rare). cancellatum typically has three to eight (with seven in the illustration in Dijkstra).

jccurd's picture

Been away

Thanks for the clarification, Roy. The Rspl stuff was beginning to addle my brain - that small part which isn't soaked in wine, that is. ;-)