Coenagrion pulchellum (Vander Linden, 1825) Variable Damselfly
This species deserves its English name, and its great variability gives rise to some
confusion with its close relative, Coenagrion puella. The structure of the genitalia seems
to be the only really reliable diagnostic feature, although some authors (e.g. Hammond,
1983, p.68) mention the strongly lobed hind margin of the prothorax (this margin is
more gently curved in C. puella). Both features require close examination. In the typical
form, the 'U' mark on the second segment of the male abdomen is stalked, whilst the 8th
segment is blue, as in C. puella, but the black marking on segment 9 is much more
extensive than on C. puella. In the typical female of C. puella, the ground colour is blue
rather than green, and the marking on the second segment of the abdomen is a
'mercury' sign, rather than thistle-shaped (see Appendix C).
The species has been so rarely met with in Essex, that to give local flight periods
would be meaningless. Hammond (1983) gives the flight period from the latter half of
May through to the beginning of August.
Internationally, both C. puella and C. pulchellum have a broadly similar distribution
in the Palaearctic Region. However, throughout this common range. C. pulchellum is by
far the most localised species, and, in the British Isles, at any rate, appears to be rapidly
losing ground. Its few remaining strongholds, such as the Norfolk Broads and the
Somerset Levels, do not include any Essex sites. A Nature Conservancy Council
publication (Chelmick et al., 1980) reports the species as 'fast declining' and as requiring
particular attention if it is not 'to reach endangered status'.
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