The genus Ischnura in Iberia
IDENTIFICATION OF MALES- Ischura pumilio is easy; you don't need voucher specimens.The illustration here (right) shows the difference. If the blue marking at the end of the abdomen is on the 9th segment (almost to the very end) the the species is I. pumilio. If the blue mark is on the 8th segment (9th segment is black) then the problems begin because I. elegans and I graellsi both occur in parts of Spain; often together.
So dear reader, taking Adolfo Cordero's comments on board, I collected a total of 42 males of these two species from about 18 localities. The results are summarised here:
So dear reader, taking Adolfo Cordero's comments on board, I collected a total of 42 males of these two species from about 18 localities. The results are summarised here:
SIZE:
- I. elegans - Ave length 31.14 mm maximum 33.0 mm minimum 29.0 mm
- I. graellsi - Ave length 28.50 mm maximum 30.5 mm minimum 25.0 mm
POST OCCULAR SPOTS (behind the eyes viewed from above)
- I. elegans - present on all specimens
- I. graellsi - not present on 78% of specimens. Present on the remainder but often small and in one case only on one side
ANTE HUMERAL STRIPES - along the sides of the thorax
- I. elegans - present on all specimens
- I. graellsi - not present on 36% of specimens. Present on the remainder but often thin or indistinct
Male Appendages
If you are in any doubt then you can check the identification by looking at the anal appendages with a hand lens. catch the specimen (males), hold them by the wings and look at the rear end with a lens:
- Upper Appendages - I. elegans (branches thick and parallel) I. graellsi (branches thin and diverging) I pumilio (branches absent)
- Lower Appendages - I. elegans outward pointing with dark inner branch I. graellsi curved inwards with no inner branch I. pumilio tiny and inward pointing
Viewing the end of the abdomen from above can also be useful:
- I. elegans (right) conspicuous and outward pointing
- I. graellsi (left) turning inwards and not beyond width of the abdomen
Females
Both I. elegans and I. graellsi have three female forms which are quite similar except that one of the I. graellsi forms looks very like the female of I. pumilio. The illustration here shows the females of I. graellsi and I pumilio and includes (right) the unusual blue form female.
Confused - well the situation is far from clear. Let us look at each of the types referred to here as A,B,C
Confused - well the situation is far from clear. Let us look at each of the types referred to here as A,B,C
Type A
I. elegans - violacea to Androchrome
I. graellsi - greenish yellow to Androchrome
I. graellsi - greenish yellow to Androchrome
Type B
I. elegans - violacea to infuscans (brown with humeral stripe)
I. graellsi - whitish almost violet to infuscans (brown with humeral stripe)
true violacea very rare in I. graellsi
I. graellsi - whitish almost violet to infuscans (brown with humeral stripe)
true violacea very rare in I. graellsi
Type C
I. elegans - rufescens to rufescens obsoleta (red to brown without humeral stripe)
I. graellsi - aurantiaca to rufescens obsoleta (orange to brown without humeral stripe)
Type C I. graellsi is very similar to aurantiaca in I. pumilio but with more black and ab.seg 8 often with blue
I. graellsi - aurantiaca to rufescens obsoleta (orange to brown without humeral stripe)
Type C I. graellsi is very similar to aurantiaca in I. pumilio but with more black and ab.seg 8 often with blue
Habitat and Distribution
This is a permanent pond along the road from Monreal del Campo to Aragon in central Spain. It's covered in duckweed, has very little emergent vegetation and is pretty much useless. Except that it has all three species of Ischnura on it and gives you an idea about just how catholic are the tastes of this genus in the Peninsula.
I. graellsi is one of the commonest and most ubiquitous dragonflies in Iberia and is found everywhere with the exception of the north east where I. elegans appears to dominate. Just how far south and west I. elegans extends is hard to say; it is good to check everywhere that you find an Ischnura; hopefully these notes will help. I. pumilio is far less common than I graellsi but can also turn up almost anywhere.
As to habitat; well the Pozuelo pond shown above gives you an idea; but sluggish rivers, well vegetated ditches in fact almost any aquatic habitats provide ideal conditions. I. pumilio is more local and appears to have a particular liking for endorreic lakes; it is often an early coloniser of newly created and cleared waters.
I. graellsi is one of the commonest and most ubiquitous dragonflies in Iberia and is found everywhere with the exception of the north east where I. elegans appears to dominate. Just how far south and west I. elegans extends is hard to say; it is good to check everywhere that you find an Ischnura; hopefully these notes will help. I. pumilio is far less common than I graellsi but can also turn up almost anywhere.
As to habitat; well the Pozuelo pond shown above gives you an idea; but sluggish rivers, well vegetated ditches in fact almost any aquatic habitats provide ideal conditions. I. pumilio is more local and appears to have a particular liking for endorreic lakes; it is often an early coloniser of newly created and cleared waters.