There area a goodly number of dragonfly species, the males of which develop a powdery blue coating on various parts of their bodies, most notably the abdomen. Since the coating is called pruinosity after the bloom that develops on the skin of fruit, we have affectionately taken to referring to such species as prunes, for short.
This is just about the commonest prune of the set. Here is a comparison of the four prunes to be found in the UK, plus two Europeans, which will hopefully help clarify the main identification differences.
The other common confusion is between immature male and female specimens, which are painfully similar. This comparison chart should help clarify.
Id Notes
- black pterostigma
- generally greenish eyes
- mature ♂ – pruinose abdomen with black tip
- stockier build than the similar O. albistylum
| male | |||
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| female | |||
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| teneral | in cop |
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This seems the most likely species for two males we saw patrolling offshore on a fresh water lake in the Gironde between the Atlantic and Bordeaux in early September. Since they were in constant motion we couldn’t pick out details, just an impression of blue/gray thorax, dark blue/black abdomen and a skimmer body shape. Are there any better candidates that fit this description? Thanks,
O. cancellatum seems about the most likely, given your description – the behaviour sounds good, as well as colour – and timing, Clive.
It can be tricky to separate the very similar O. abistylum (White-tailed Skimmer) at a distance, which would still be possible though September is later in its season. That latter tends to look paler than its cousin, though.