Identification of Small Red-eyed Damselfly
* Small Red-eyed Damselfly Erythromma viridulum has now made it into Leicesterhsire & Rutland - first recorded at Priory Water on 22nd July 2006.
I happened to be in Kent on 11th August 2002, and, remembering that Small Red-eyed Damselflies had been reported in the last few weeks, thought that I'd check out Bluewaters Shopping Centre. I found over 20 of them without any problem at all, at what proved to be an excellent site.
Bluewaters is located just north of the A2 between Dartford and Gravesend. It's only a couple of minutes from the A2 to the site, and only a couple of miles from the M25, making it a perfect stop-off point if using either of these roads on a sunny day in August.
If travelling east along the A2 take the first exit after the M25. Bluewaters is very well signposted from here. The complex is only a mile north of the A2 in quite a spectacular setting, being constructed in a huge, disused quarry and thus surrounded on all sides with high chalk cliffs. I drove around the site to one of the carparks at the western-most edge. The area is fantastically landscaped, with a series of water features draining at successively lower levels to the west. The large lake in the north west corner of the complex is planted with Yellow Water-lily and it is here where I found the damselflies. The lilies are very close to the lake shore and are therefore excellent for studying the Small Red-eyed Damselflies, which occur alongside their Red-eyed cousins and provide perfect comparison.
I was particularly interested to study the identification of this species as it is rapidly spreading north and west and could well turn up in Leicestershire and Rutland before too long. My field guide does not include this species so, at the risk of 'teaching you to suck eggs', I've attached an extract from my notebook (sorry about the scanned-in quality) and a few notes on features which I found useful. You've now got no excuse for not going out and finding one in Leicestershire!
Male Small Red-eyed Damselfly, Bluewaters Shopping Centre, Kent, Aug 2002 © Mike Hunter
Habits and Jizz
Small Red-eyed Damselflies prefer to sit horizontally on floating vegetation (e.g. water-lilie leaves) in a manner identical to Red-eyed Damselfly. Similarly males defend a small floating territory and fend off rivals, making short flights out over the open water.
Small Red-eyed Damselfly is essentially a miniature version of Red-eyed Damselfly. Size and structural differences are quite noticeable, however, with Small Red-eyeds being comparable to Common Blue Damselfly in both respects. They therefore lack the heavy, robust quality of Red-eyed being a delicate insect more akin to the other smaller damselfly species. This feature is apparent in flight as well as at rest.
Detailed Comparison (based on observations of adult male insects)
Although adult males of both species are generally black damselflies with red eyes and a blue band at the tail tip, there are many subtle, diagnostic differences that can be used to separate the species with relative ease. All of the following features can be observed with binoculars or telescope and there is certainly no need to examine insects in the hand to confirm identification.
Though both species are 'red-eyed' the actual tone of the red pigmentation is quite different. While Red-eyed Damselfly has deep, blood red eyes those of Small Red-eyed are much less intense in colour, being a paler orangy-red. In the latter species this has the effect of making the darker 'pupil' in the centre of the eye more obvious.
Detailed comparison of the thorax reveals a number of subtle differences in the markings on the lateral surfaces, but these are of much less value than those found on the abdomen and are not listed here.
The sketches below, copied from my notebook, show that although the abdominal segment No 1 is wholly blue on both species, segment No 2 is markedly different. Segment No 2 on Red-eyed Damselfly is wholly black, with just a small blue area at its rear-end. Segment No 2 on Small Red-eyed Damselfly is, in contrast, almost wholly blue with a single broad black line running along its upper dorsal surface.
Red-eyed Damselfly - male
Thorax and abdominal segments 1 and 2 |
Small Red-eyed Damselfly - male
Thorax and abdominal segments 1,2 & 3 |
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Similarly, segment No 8 shows a great contrast between the two species, and is probably the most easily observed distinguishing feature. In Red-eyed it is almost wholly black with just single broad blue band running along its lower surface. In Small Red-eyed it is almost wholly blue with a large black mark on its upper dorsal surface, forming a wedge shape which tapers in width towards the rear of the abdomen. Segments 9 and 10 and wholly blue on both species, but another useful identification feature is the distinctive bulge in the segments 8, 9 and 10 displayed in Small Red-eyed. This bulge contrasts with the slim central abdominal sections to give a bulbous-tipped profile similar to that found in Blue-tailed Damselfly. Red-eyed Damselfly is markedly different in this respect, having a distinctly thick and parallel-sided abdomen throughout its length.
Red-eyed Damselfly - male
Abdominal segments 8,9 and 10 |
Small Red-eyed Damselfly - male
Abdominal segments 7,8,9 and 10 |
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