Wednesday, 6 August 2014

A most distinguished visitor

On Wednesday the Kingfisher Trap came into its own again. Perched on the tip was a large black-and-yellow dragonfly. A box-like projection on the end of his body suggested a Pincertail. Two species of Pincertail are found in this part of France: the Small Pincertail Onychogomphus forcipatus Onychogomphe à pinces (Green-eyed Hooktail) and the Large Pincertail Onychogomphus uncatus Onychogomphe à crochets (Blue-eyed Hooktail). Both species are at the northern limit of their range and rare; uncatus very rare. This individual was a male, in beautiful condition. He stayed for at least a couple of hours, taking short aggressive flights whenever another dragonfly of any species came too close.

The "Kingfisher trap" comes into its own again

Tim took a good look through binoculars and dashed for "the bible" of European dragonflies:
the aptly named Field Guide to the Dragonflies of Britain and Europe
(Klaas-Douwe B Dijkstra and Richard Lewington. BWP 2006).
Yes, it was a Large Pincertail. Everything we could see checked with Dijkstra:
  • grey/blue eyes, grey indicating recently emerged,
  • extensive broad parallel black lines on side of abdomen, rather than broken, narrow black lines, 
  • yellow stripes on back connected dorsally, 
  • four cells in the anal triangle of the wing rather than three,
  • lower cercoid ("pincer") on tail smoothly rounded rather than square and boxy, and outside the upper "pincer" rather than inside.

The following day the pincertail was there again, chasing away potential rivals, i.e. any other large dragonfly.

Wikipedia describes the distinguishing features of the Large Pincertail thus:
The eyes of Onychogomphus uncatus are widely separated and bright-blue or gray-blue eyes, never green. The front black line on the side of the thorax does not touch the midline. The yellow collar at the front of the thorax is interrupted by a black bar. It has four cells on the anal triangle of the rear wing, but no yellow line on the 'vertex'. 'Cercoids' are always yellow.

This is what we saw
Identifying features clockwise from top left: cercoids, cercoids again,
anal triangle (veining of the wing next to the body, in the centre of the picture), parallel lines on abdomen

On 21st July 2013 last year, we were visited by a member of the same species. It first came to our attention because this large dragonfly was sitting on the frame of the front door. It had trapped itself in the house and worn itself out beating at the window glass.

The identification points are clearer to see in these photos because the beastie was cooperative and sitting quite still and close by...
not halfway across a millstream!!
He is actually sitting on the path outside the front door. After a few minutes rest he flew away.

These two visits are the first and second confirmed reports of the species in Faune Touraine. The dragonflies section of the site has only been operating for a short while, so it's not that difficult to get a "first", but this animal is genuinely rare.

We haven't seen him since, so the second half of July seems to be the time to visit us if you are a lover of libellules.


Susan said...

Excellent observation and record. I've just compared him to my pics of the Small Pincertail at your place and the differences are clear.

Tim said...

I rhink we need to log your Small Pincertail sighting too. P.

Amelia Frenchgarden said...

It is a very distinctive looking dragonfly. Nice to have caught something rare and to have added to the information on its range. Amelia

Anonymous said...

Fascinating pictures and very informative, thank you.

Tim said...

the Faune recording sites now include Charente...
no Bee records [but they might follow - the dragonflies suddenly appeared!]...
however, there is a section for your amphibians.
Firsts or no.... 'tis the recording of sightings of anything that is important...
it builds up data for researchers in this time of major climate change.

Philip, thanks....
Pauline put a lot of work into this. Make sure that you record your sightings on the various Natural History Museum data collection points...
you are perfectly positioned to record firsts for Northerly movements from Europe.