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Description This is a robust damselfly in which males are mostly black with blue markings
and bright red eyes, and so cannot be confused with any of our other resident
species. The dorsal surface of the thorax is bronze-black, with no antehumeral
stripes. The sides of the thorax are blue, as is the dorsal surface of abdominal
seyments 1, 9 and 10. In the similar Ischnura elegans, only abdominal segment
8 is blue dorsally. In mature females the eyes are not as bright as in males, and
the blue markings on the abdomen are lacking, apart from a thin blue ring
dorsally between several posterior segments. The sides of the thorax and
abdomen are yellowish green.
Breeding biology The males are aggressive and fly purposefully and low over the water surface
in search of females. Both sexes frequently settle on floating leaves, though in
males Seldom on the same leaf. Winsland (1983) and Benton (1988) record
interspecific competition between E. najas and Enallagma cyathigerum.
Oviposition occurs in tandem, the eggs being inserted into the stems of
aquatic plants. Winsland (1983) noted that a pair of E. najas in tandem remain
submerged for 28 minutes. The larvae, which live amongst submerged water
plants, generally take two years to complete their development, but can take
one year.
Flight periods E. najas is on the wing from mid-May to the end of August. In south-eastern
Britain it may be found with many other dragonfly species, such as Anax
imperator, Aeshna grandis, Libellula depressa and the commoner damselflies.
Status and distribution E. najas is numerous in the Weald, and fairly common in some other
south-eastern and midland counties. It extends north to the Pocklington and
Leven Canals in Yorkshire, and has a toe-hold in Wales along the Montgomery
Canal. It is a very rare breeding species in the south-western peninsula of
England. A single female specimen, apparently taken at Bridge of Weir
(presumably Renfrewshire, Scotland) on 13 June 1885, is in the JJ F X King
collection (O'Farrell 1950). This record, and those of several other species in
the collection, has not been mapped (see Vetting of records section in
Description of data set). It was recorded as Irish by Haliday in the 19th
century, but its status was regarded with scepticism by King and Halbert
(1910) and Nelson (1986).
European and world
distribution
Erythromma najas (Hansemann) Red-eyed damselfly
Habitat E. najas is most often recorded from those mesotrophic lakes, large ponds,
canals and dykes where there is plenty of aquatic vegetation with floating
leaves, such as water-lilies, broad-leaved pondweed or amphibious bistort. It
also breeds in sluggish rivers, provided the current is sufficiently slow not to
prevent the growth of the above-mentioned plants.
Erythromma is one of the few genera which is confined to the Palaearctic
region. E. najas is widespread throughout central and northern Europe, but is
absent from most of the Mediterranean area. Its range extends east to Siberia
and Japan.
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