Beauty by Name, Beauty by Nature

Male Beautiful Demoiselle, Calyopteryx virgo

The largest Irish damselfly, the Beautiful Demoiselle (Calopterxy virgo), is also (in my opinion) the most beautiful - something to be said when compared with such beguiling creatures such as the Large Red Damselfly and the Emerald Damselfly. A sexually dimorphic species, females are of a lighter hue than males, both a dark metallic  blue-green colour. The wings are a dark brown, but can appear blue or black depending on how the light hits them, and such opaque wings, combined with its slow deliberate flight means C. virgo is commonly mistaken for a butterfly (1).
C. virgo has a distribution through out most of Europe except for the far north (2) and this is also true for Ireland where it is resticted to the south of the country, demarked by a line from Dublin to Clew Bay in Co. Mayo (1). Where it does occur, it often crosses territories with its close relative the Banded Demoiselle (C. splendens). Although similar in appearance, these C. splendens lacks the fully opaque wings of C. virgo (having just a band of colour, hence its common name. C. virgo also has a greener colour, brought about by the wax crystals covering the epicuticle (3).
The close proximity of these relative species often lead to hybridisation (4). Generally, such hybridisation is believe to be driven by sexual selection by females of either species but it has been shown that males, through forced copulation, may be responsible for hybridisation between C. virgo and C. splendens (4).

References:

1. Nelson and Thompson, 2004. The Natural History of Ireland's Dragonflies pp. 76-83
2. Gibbons, 1999. Insects of Britain and Europe p. 25
3. Kuitunen and Gorb, 2011.  Zoology 114 pp. 129-139
4. Tynkkynen et al., 2008. Animal Behaviour 75 pp. 1431-1439