|The genus Chalcolestes is separated
from Lestes because of differences in their larvae.
Chalcolestes viridis (Vander Linden,
1825), formerly Lestes viridis (Vander Linden, 1825), is a damselfly of
the family Lestidae. It has a metallic green body and at rest it holds
its wings away from its body. Its common name is the Willow Emerald Damselfly
or the Western Willow Spreadwing.
Length in male 42-47mm and in female
39-44mm. This damselfly is metallic green, with no blue pruinescence on
the male. At rest, the Emerald damselflies all spread their wings at an
angle to the body, unlike other damselflies. The pterostigma is pale brown
with a black border, and the sides of the thorax show a spur-shaped marking.
The male upper appendages are distinctively pale cream with dark tips.
A closely related species C. parvidens
(Eastern Willow Spreadwing) used to be considered a sub-species of C. viridis.
C. parvidens occurs in Greece, Bulgaria, Croatia and in Italy; near Rome
it flies with C. viridis in the same ponds. There are small morphological
differences between the two species both as adults and larvae and analysis
of proteins from the two species, by electrophoresis, also supports their
separation into two species, but they are hard to tell apart in the field.
C. parvidens flies earlier in the year than C. viridis.
C. viridis is found across southern
and central Europe. In the eastern mediterranean it is replaced by C. parvidens
with areas of overlap in Italy and the Balkans. C. viridis is found on
many mediterranean islands including Corsica, Sicily, Mallorca, Menorca
and Ibiza, in the Maghreb in North Africa, Turkey and the Middle East.
However many of the old records for C. viridis in the east of its range
could be for C. parvidens. In Britain it was a rare vagrant and is now
a new colonist. It is widespread on Jersey
It occurs in still or slow flowing
water in ditches, ponds, lakes and canals, with overhanging willows, alders
or birches, which are used for breeding. Of all the European Lestes it
is the species, along with C. parvidens, that will lay eggs in where there
is running water. The adults are often found in the bushes which grow over
or alongside water.
In the field it is not possible to
reliably distinguish C. viridis from C. parvidens. Both species are mainly
metallic green, like other Lestes damselflies, but larger and darker but
they do not have a powder blue pruinescence which is common in other Lestes.
The pterostigma is pale brown and outlined in black. The thorax has thin
yellow antehumerals and broader yellow stripe above a thin black line on
each side; the upper edge of the stripe is irregular. Both C. viridis and
C. parvidens have a prominent spur-like marking on the side of the thorax.
Male - The abdomen is very long.
The lower anal appendages are less than half the length of the upper which
are a distinctive pale yellow with black tips.
Female - The ovipositor is longer
than in Lestes dryas.
Flight period is late from August
to October although in the southernmost parts of its range it can occur
as early as May and persist until November.
Mature males defend vertical territories
in marginal shrubs and small trees where they find and mate with females
in the normal damselfly manner forming the wheel position. Egg laying occurs
with the pair in tandem, the eggs being laid into incisions in the bark
of overhanging branches, not into submerged vegetation as is the case in
many damselflies. Egg laying can result in distinct oval galls forming
in the shrub's bark. The eggs develop rapidly for a few weeks and then
enter a diapause state. In this state the eggs development is very slow
and it is in this state that the eggs overwinter. The following spring
the eggs hatch, the larvae drop into the water and start to develop. Growth
is rapid and adults can emerge in a couple of months. After emerging the
adults move away from water to mature. In this stage of their life-cycle
the immature adults cannot breed. The adults need a period of time for
their reproductice organs to develop and this non-breeding period also
stops the adults breeding too early in the season. If the females lay eggs
early in the year the eggs will develop when it is to warm to for them
to enter diapause. They might hatch out before winter and the resultant
larva will die when winter temperatures occur. When fully mature the adults
return to water and start breeding.