is typically with wings spread out. are known as 'dragonflies' (in the narrower sense).
Anisoptera (see Appendix C). The Anisoptera are further divided into two groups which
are named according to behavioural differences. The 'hawker' dragonflies are generally
the larger Anisoptera species which spend most of their active time hawking for insect
prey, and settle only rarely. When they do so, they typically land vertically, with the
wings spread out at right angles to the body. The usually smaller 'darter' dragonflies
typically rest with the body more-or-less horizontal. Whilst the insect is perched the
wings may be held outspread as in the hawker species, or. when fully at rest, swept down
and forwards (Appendix C). Darters typically spend much of their time on perches,
'darting' off at intervals, and frequently returning later to the same perch.
The species of Zygoptera occurring in Britain belong to four families - the
Calopterygidae (the 'demoiselles'), the Lestidae (the 'emerald' damselflies). the
Platycnemididae (one species only - the White-legged Damselfly). and the
Coenagriidae (includes the various blue-and-black patterned damselflies). Among the
Anisoptera, the hawkers include four families, the Gomphidae, the Cordulegasteridae,
the Aeshnidae and the Corduliidae. The majority of the species of hawker dragonflies
found in Essex belong to the Aeshnidae. The darter dragonflies are grouped together
into the family Libellulidae, which is now further divided into three genera with species
found in Essex: genus Libellula ('chasers'), genus Sympetrum ('darters') and genus
Orthetrum ('skimmers').
The British Dragonflies
There are some 5,500 species of Odonata world-wide, but the majority of these are
tropical or sub-tropical species, and the British dragonfly fauna is relatively poor, even
by continental European standards. At the present time there are believed to be thirty
eight breeding species in Britain (excluding Ireland, which has a further species -
Coenagrion lunulatum - only recently discovered). A further three species formerly
occurred here but are now believed extinct. One of these. Coenagrion scitulum (the
Dainty Damselfly) was only known from Essex. Finally, there are three species of rare
migrants which are occasionally recorded in Britain, but which have not (yet)
established stable breeding populations. Two of these species. Sympetrum flaveolum (the
Yellow-winged Darter), and Sympetrum vulgatum (the Vagrant Darter), have very
occasionally been recorded in Essex.
Of the thirty-eight established breeding species, four are Arctic species, confined to
Scotland. A further five or so are species of acid bog. with a predominantly westerly or
south-westerly distribution in Britain. Some of these species, such as Ischnura pumilio
(the Scarce Blue-tailed Damselfly) and Coenagrion mercuriale (the Southern Damselfly)
are essentially Mediterranean species at the very northern limit of their range. Some
with very restricted distribution in southern Britain, such as Gomphus vulgatissimus (the
Club-tailed Dragonfly) and Aeshna isosceles (the Norfolk Hawker) appear to be
restricted more by their specialised habitat requirements than by climatic factors.
None of the species currently breeding in Britain appears to be in imminent danger of
extinction, although several (including Coenagrion pulchellum (the Variable Damselfly)
and Platycnemis pennipes (the White-legged Damselfly) appear to be in serious decline,
largely through pollution or other modifications of habitat. Others, such as Aeshna
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