NOTES ON SOME SOUTHERN FRENCH DRAGONFLIES

The observations described here are done in Lambeyran (close to Lodève), Octon (near Lac du Salagou) and le Bousquet d'Orb. Height above sea level from around 200m (Octon and le Bousquet) to 400m (Lodève). This region forms the boundary between the mediterranean climate and the more mountaineous climate north of it. The places can be found on map 65 of the French topographical maps (TOP100, 1:100 000) or on map 2643 OT (TOP 25, 1:25 000). Exact geographical coordinates (Greenwich system) of the rivers and small streams are: 43°44 north and 3°16 east for Lambeyran, 43°40 and 3°17 for Octon, 43°41 and 3°10 for the river Orb.

AN EXTRAVAGANT ONYCHOGOMPHUS FORCIPATUS

Early in the morning on a stony path many dragonflies were taking a sunbath. Most abundant were both Onychogomphus species: O. uncatus and O. forcipatus unguiculatus (forcipatus is on the upper picture). Then I saw a much yellower beast. From a distance the first recordings were made (second picture), but then it flew away and it did not come back. Back at home I concluded that it should be a (young) Ophiogomphus cecilia, because of the amount of yellow on the prothorax and the marks on the abdomen. But it was quite far away from the known recordings of this species in France. I contacted Jean-Louis Dommanget and he was more suspicious than I was. A closer look led to the conclusion that it is an Onychogomhus forcipatus that misses much of the black markings on the prothorax. But it does not miss the second yellow stripe between the eyes that is so characteristic of this species... I had overlooked that and the lesson again is: always be aware of individual animals that are very different. They do not read our determination books to learn how they should be coloured.
The third picture shows in blue what approximately is black in this species, in stead of yellow in this individual.

COLOURATION OF XANTHOSTOMA WINGS

juvenile males splendens

juvenile males xanthostoma

There is no consensus yet on the status of xanthostoma: is it a species (Calopteryx xanthostoma) or a subspecies (C. splendens xanthostoma)? Visiting the river Orb in the south of France in the second half of june 2002, I again was struck by how different in young males the colouration process is compared to (Dutch) C. splendens splendens. I made some video recordings to pick out different colour-phases and back at home I made recordings of splendens.
Fresh males of splendens immediately show a dark blue spot on the wings. The two pictures left show the same first day animal. (All Calopteryx pictures can be seen enlarged by clicking on them, ± 50 K each.) Such young males of xanthostoma I have not seen, but the youngest show a brownish wing without any trace of the dark spot. Completely different from young splendens.
Shown to the right is a series of the colouring process in xanthostoma. The dark spot slowly emerges. In this phase the animals are very difficult to approach, compared to both younger males and adults. They are in the mean flying more away from the shore (10-20 metres). Are they being seen by adults as rivals and are they trying to avoid attacks?
In reality and on video it was easy to see that the animal on the second picture already was showing the dark spot emerging, but here on the picture it is hardly visible. On the third picture you can see it.

adult males splendens

adult males xanthostoma

The last pictures show the adult males of splendens (to the left) and xanthostoma (to the right), with the end-phase of wing colouring. The splendens is rather young (second day?) and has almost clear wings. The xanthostoma males are of different age and the first still shows a bit brownish colour of the hyaline parts of the wing.

VARIATION OF CORDULEGASTER BOLTONII

So deep in the south of France I expected the subspecies immaculifrons of Cordulegaster boltonii, but they were too dark. And varying. Unfortunately I cannot show the variation range. Some even had less yellow than the left picture, others had rather much more yellow than the other picture. In this mediterranean region west of the river Rhône the animals seem to be of the Cordulegaster boltonii boltonii subspecies. Maybe the yellower animals indicate that the overlapping zone of the subspecies is near. Note especially how much black segment 6 contains (it is the segment over the whitish branch on the left picture).
When you click on the thumbnail to the right you get a large combined picture of a typical boltonii of this region (45K, 905 pixels high). I did not try to fill in missing parts of the wing and did not try to make it smoother. It shows how remarkably sharp some video frames are.

Weia Reinboud (weia (at-symbol) antenna (dot) nl) (See my index page in case it is not yet open.)