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IMIVLIGRANTS AND ACCIDENTAL
SPECIES [See also footnote on p5.]
The populations of several species resident in
Britain and Ireland are reinforced in some years by
immigrants from the continent, notably Aeshna
mixta, Libellula quadrimaculata, Sympetrum
striolatum and S. sanguineum. There are also several
other species which have occurred as immigrants
and accidental visitors; none of them has so far
succeeded in maintaining a permanent breeding
population in Britain and Ireland, though several
have bred in the Channel Islands. They include
some of the most likely candidates to be discovered
in, or to colonise, Britain or Ireland in the future.
Lestes viridis (Vander Linden)
This species is similar to L. sponsa and L. dryas in
having a predominantly metallic green body, but is
larger than either of them, and mature males do not
develop any blue pruinescence (or only negligibly
so). L. viridis breeds in ponds, canals and slowflowing
streams and rivers. Males defend vertical
territories in trees overhanging the water margin.
The female lays her eggs in the smaller branches of
marginal bushes such as sallow It is on the wing
from early July to late September. The only British
record is of a male captured at Shenley, Hertfordshire,
on 11 August 1899 by E R Speyer. It was
recorded at a number of localities on Jersey in the
1940s (Le Quesne 1946), and was rediscovered
there in 1989; breeding was confirmed in 1990. On
the continent, L. viridis is found throughout southern
and central Europe as far north as Belgium and
Germany It occurs in the Middle East and North
Africa.
Aeshna affinis (Vander Linden)
A. affinis is a small aeshnid, similar in size and
general appearance to A. mixta, but the coloration of
the abdominal spots of males is much brighter blue,
highlighted by the black surrounds. Also, the
pattern of these markings is different, most
noticeably on the anterior segments. Additionally
the sides of the thorax are different in colour and
pattern from A. mixta. It breeds in shallow ponds
and ditches which possess an abundance of
emergent vegetation, such as horsetails. It is a
migratory species and is on the wing from late June
to the end of August. There is only one confirmed
British record, of a male, being taken at Romney
Marsh, Kent, on 5 August 1952 by W E Dyson. The
specimen is in the Natural History Museum, London.
A field observation in 1992 (Holmes 1993) highlights
the need to net a specimen and examine it
carefully in the hand for records of critical species to
be acceptable. On the continent, the distribution of
A. affinis is centred on the Mediterranean region. It
is found east to China, and also in North Africa.
Hemianax ephippiger (Burmeister)
H. ephippiger bears a superficial resemblance to
Anax imperator on account of the longitudinal black
line, of irregular width, on the mid-dorsal surface of
the abdomen. This line extends laterally on posterior
segments, enclosing a pair of large pale spots on
segments 8-10. It is a smaller dragonfly than A.
imperator and, in males, the body is a sandy brown
colour except for abdominal segment 2 which is
bright blue in mature individuals. In females, the
abdominal coloration is darker and duller, and
segment 2 has only a weak blue-violet tinge. It
breeds in small ponds. In Europe, H. ephippiger is
observed mainly between March and October. It is
strongly migratory and, until recent years, had been
recorded on only six occasions in Britain, including
once in the Shetland Islands, and on one occasion in
Ireland (Merritt 1985). Since then a further six
records have occurred, three of which were in 1988.
The remaining three records were from Hampshire,
Cambridgeshire and Devon, the latter record being
of a male taken at Plymouth, Devon on 8 January
1992, and subsequently sent to the Natural History
Museum, London. These recent records are reviewed
by Silsby (1993). In Europe, H. ephippiger breeds
sporadically in the Mediterranean region. Elsewhere
it is a vagrant, and the only species of dragonfly to
have been recorded from Iceland. It breeds in the
drier regions of Africa, the Middle East and east to
Pakistan.
Gomphus flavipes (Charpentier)
G. flavipes is very similar to G. vulgatissimus, but the
abdomen is yellower and less club-shaped. Also, the
black thoracic markings are slightly but significantly
different, and the legs are yellow, striped
longitudinally with black, unlike G. vulgatissimus in
which they are almost entirely black. It breeds in
rivers, and is on the wing from mid-June to early
September. There is only one British record, that of a
male taken near Hastings, Sussex, on 5 August 1818
by J F Stephens. In Europe it occurs mainly in the
east, with only a few scattered records in the west,
where it appears to be declining. It is an eastern
Palaearctic species, ranging from eastern Europe and
the Middle East to Manchuria.
Sympetrurn vulgaturn (Linnaeus)
This species is similar to, though slightly smaller than,
S. striolatum. However, in mature males, the abdomen
is more reddish and more constricted in the middle
segments, though not to the extent of male S.
sanguineum. Also, the tiny paired black spots on the
dorsal surface of the abdomen are not enclosed in
yellow rings as in S. striolatum. The black transverse
line at the top of the frons extends down the inner
sides of the eyes, unlike S. striolaturn in which there is
no lateral extension or, at most, a smudge. The