|Aeshna caerulea (Strom, 1783), the
Azure Hawker, is one of the smaller species of hawker dragonflies (family
It is 62 mm long. Both sexes have
azure blue spots on each abdominal segment and the thorax also has azure
markings. The markings on the male are brighter and more conspicuous than
in the female. The female also has a brown colour form. This species flies
in sunshine, and will also bask on stones or tree trunks. It shelters in
heather or similar low vegetation in dull weather. The flight period is
from late May to August.
The Azure Hawker is a relatively
small aeshnid, similar in size to the Blue-Eyed and Migrant Hawkers (Aeshna
affinis and A. mixta). Its thorax is essentially brown, with short and
weakly-developed antehumeral stripes, while the spots on its abdomen are
a bright blue in the male and usually yellow in the female. Aeshna caerulea
occurs at high latitudes (in Scandinavia and Northern Scotland) or, in
Central Europe, at high altitudes (in the Alps and Dolomites). To survive
in such cold conditions it has the typical habit of basking on bright and
flat surfaces, by pressing its body against e.g. the bark of a birch tree.
Failing that, e.g. above the tree line in the Alps, its preferred perch
is a sun-exposed rock. The species also has the capacity - maybe more than
any other European dragonfly species - of regulating its body heat by changing
the colour of its abdominal spots. When it's warm and sunny, those spots
are typically light blue in the male; when it's cloudy and cold, the spots
are a much darker, duller, chocolate brown colour. Dark colours absorb
more light than light colours, and light-absorption helps to generate body
This species can be found in alpine
and arctic moors, heaths and tundra. It breeds in bog pools and sedge swamps,
and is seldom found below 1,000 m in the Alps.
There are a number of conservation
measures already implemented for Aeshna caerulea, including monitoring
its population trends and range. However restoration and conservation of
its habitat are required as it is declining in some areas of its range,
particularly in central Europe.
IUCN Red List access as Least Concern.
The species is widespread in the Eurasian polar region. Though locally
scarce and declining, particularly in central Europe, as a post-glacial
relict and thus listed in threat categories of regional red lists.