APPENDIX C
KEY TO THE IDENTIFICATION OF ESSEX DRAGONFLIES
The Order Odonata includes both damselflies (Zygoptera) and dragonflies
(Anisoptera). All adult dragonflies and damselflies have long abdomens, two pairs of
large, scale-less and membranous wings, with many cross-veins, two large compound
eyes on the head, and very short, inconspicuous antennae. They are unlikely to be
confused with insects of any other order represented in Britain.
The following key is intended to help beginners with the identification of any adult
dragonfly or damselfly which might reasonably be expected to occur in Essex. Several
British species which are extremely unlikely to be met with in Essex are excluded, so
that if the reader's interest takes her or him beyond the county boundaries, purchase of
one or other of the available field guides is strongly recommended.
As far as possible, technical terms have been avoided, but if confusion arises, the
reader may refer to the anatomical figures 2:1 and 2:2. I have included in the key all
species which have been recorded in Essex since 1980. In addition, I have included
species such as Coenagrion scitulum which were formerly resident species but appear
no longer to be so. It is very unlikely, but still just possible that they may be encountered
in the future. I have also included all three of the rare migrant Sympetrum species, even
though one of these. S. fonscolombii, has never been recorded in the county. The
rationale for this is that, being migratory species, all three might well turn up almost
anywhere, and it is as well for readers to be aware of their existence. On the other hand. I
have excluded several species, such as Ceriagrion tenellum. Orthetrum coerulescens, and
Libellula fulva which have been recorded in Essex many years ago. but not since.
Because of the general pattern of distribution of these species in Britain, and the lack of
sufficient suitable habitat in Essex, their reappearance seems to be an extremely remote
possibility.
One complication in constructing a key to the Odonata is that the males and females
of several species are very different in appearance. In most cases. I have arranged the
key in such a way that males and females of these species key out separately. However,
since the females are usually more cryptically coloured, the males are often more
noticeable in the field, and are distinctively coloured. This is true of the Sympetrum
species of dragonflies, and especially so of the large group of blue-and-black
damselflies. For this latter group in particular, beginners are strongly advised to test out
the key using the males only. Matters are further complicated by the existence of several
common colour-variations in some species, and by the fact that colour in most species
varies considerably with age. This may mean that the key simply will not work with
some specimens and a more advanced text, giving more anatomical details and using
venation will have to be consulted. So far the key is largely untried, and I would be most
interested to hear of any problems which arise in its use.
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