|Erythromma (Brighteyes) is a genus
with only three species, all with a Euro-asian distribution. The genus
has previously been considered to host only two species, both with males
having red eyes. These are Erythromma najas (Large Redeye) and E. viridulum
A third species, E. lindenii (Blue-eye)
has been added due to similarities in the genes, but more obvious also
in behaviour and the males upper appendages, with the two other species.
As this species does not have red eyes, the name Brighteyes has replaced
the name Red-eyed Damselflies.
The two Redeye-species looks a lot
like Bluets (Coenagrion and Enallagma species), but they are all black
on top of backside of the head. Only young individuals may have faint postocular
spots. The Blue-eye has very narrow postocular spots, compared to Coenagrion,
but also compared to Enallagma cyathigerum, which it probably resembles
Erythromma najas (Hansemann, 1823)
is a member of the damselfly family Coenagrionidae. It is one of the two
European species with red eyes and with a body without a dominant red colour
(for males, females have brown eyes). The thorax and the two last segments
of the abdomen (S9 and S10) are bright blue. Males do not show antehumeral
stripes on the upper side of the thorax, they are limited on females. The
other segments of the abdomen are a dull greyish colour.
The male resembles blue-tailed damselflies
(Ischnura species) but is distinguished by its large, spaced eyes that
are a deep red. It is very similar to the Small Red-eyed Damselfly (Erythromma
viridulum). This last species, which is a slightly smaller size, emerges
about one month later. Its geographical range extends more southwards.
It shows antehumeral stripes, a shiny abdomen with blue colour on the sides
of abdomen's segments S2 and S8 (this area is greyish on the Red-eyed Damselfly).
The upper side of the legs is often a pale colour (it is dark greyish on
the Red-eyed Damselfly).
E. najas and E. virulum looks very
similar, but they differ both in size and extend of black markings on the
abdomen of the males. In the picture bottom right, the faint antehumeral
stripe (on top of the thorax) of E. virulum is seen, a stripe which E.
Male E. najas (top) and E. virulum
(bottom). The two males are vey similar, but the former is a larger and
a more stout species. The dark patterns on the top of the abdomen differs,
as E. najas is all dark on the 8th segment and all blue on the 9th and
On the top of the 10th segment E.
virulum has a dark x-marking, and it is seen how the 8th is blue up on
the sides, and only black on top.
The females of E. najas and E. virulum
differ in that the former has an incomplete antehumeral stripe, and the
latter a complete stripe.