DRAGONFLY RECORDS PLEASE!
In 2001 the exciting discovery of
a new species of dragonfly for Suffolk was made. 
The arrival of the Small
Red-eyed Damselfly Erythromma viridulum from Europe was well
publicised. It was first found in Essex in July 1999 (Dewick & Gerussi
2000). In Suffolk it was at Thorpeness Mere on 29th July 2001 (Parr, pers comm.), with other sightings along the coast from Felixstowe to
Lound, and inland along the Waveney Valley to Shipmeadow. In 2002 the species
continued its colonisation into west Suffolk. Its familiar Suffolk counter
species, the Red-eyed Damselfly Erythromma najas, is also
expanding its range in some areas so detailed recording of both species is
required.
Field Characters
Both Erythromma species
are most often found over open water, away from the banks. They typically spend
much of their time perched and resting on the leaves of floating vegetation and
mats of surface algae. These mats are used by males as territorial platforms to
defend against rivals. E.najas males are easily forced to the margins of
lakes by the more aggressive Common Blue Damselfly Enallagma
cythigerum. E. viridulum appears more aggressive and seems to hold
its own better, especially when in numbers and is often further out in the
water.
The red eyes and blue tip to the
abdomen are conspicuous through binoculars at some distance and make
identification of males of both Red-eyed Damselflies easier. Some differences
between the species can be made at this distance but closer inspection is
needed to verify the species. The males of the Blue-tailed Damselfly Ischnura
elegans can resemble the E. najas in coloration but lack the very
distinctive red eyes.
E. viridulum seems to
prefer eutrophic ponds, lakes and some dykes and ditches with plenty of Hornwort
Ceratophyllum, Water Milfoil Myriophyllum and Mare’s-tail Hippuris
vulgaris. It is often the dominant species at a site and can number over a
thousand individuals at a site.
Identification
Adult E. najas appear more
robust than other damselflies including E. viridulum; this is
particularly noticeable when able to compare both species. The males of each
species are easiest to identify; the best character in E. viridulum is
the fresh blue sides to the abdominal segments two and eight. In E. najas
these are black, this can be seen at some distance. The eye colours are also
different in the two species: in E. najas they are burgundy red, while
in E. viridulum they are more like the colour of tomatoes. In males
examined in the hand or at close range, the dark ‘X’ mark on the upper surface
of the blue abdominal segment 10 is diagnostic; in E. najas it is blue
all over.
As with many other damselflies,
females are mainly seen in tandem or ovipositing at the water, and are hard to
identify other than in the hand. They can be mistaken for Coenagrion
species. The most distinctive feature for this is the shoulder stripe, which in
E.viridulum is complete and in E.najas looks more like an
exclamation mark or a reduced line.
Flight period: E. najas:
from mid-May onwards; E. viridulum; from mid-July onwards.
I am keen to gather as much detail of its spread across
the county as possible so am requesting that those who have been fortunate to
find it in the last two years, to please send me their records, so a thorough
report can be produced for the next Transactions.
Norfolk Hawker (Anisaeshna
isosceles)
This is another species I would
like records of please. This species is restricted to Norfolk and Suffolk and
is well known in Suffolk in the lower Waveney Valley. Here it is often seen
hawking over the unspoilt grazing marshes, favouring dykes with a rich aquatic
flora. However it appears to be expanding its range in Suffolk and as an
endangered species more knowledge of its range will be important for helping to
plan for its future survival.
Identification:
A .isosceles is a large
brown dragonfly similar to the Brown Hawker (A. grandis), but with clear
wings, green eyes and a yellow triangle on segment two (hence isosceles),
this distinguishes it from the much commoner Aeshna grandis, this has
distinctive amber wings a brown body with blue spots on the side of the abdomen
and blue tinted eyes. A.isosceles flies from the beginning of May up to
early August some into late August while A.grandis flies from mid June
to October.
Any other records of Dragonflies
from across the county would be gratefully received.
Toby Abrehart, Dragonfly Recorder, 46-48 High Street,
Wrentham, Suffolk NR34 7HB
E-mail: Toby@Abrehart.fsbusiness.co.uk
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