The emperor dragonfly or blue emperor (Anax imperator) is a large species of hawker dragonfly of the family Aeshnidae. It is the bulkiest dragonfly in most of Europe, including the United Kingdom,[1] although exceeded by the magnificent emperor (A. immaculifrons – very marginal range in Europe)[2] and in length by females of the golden-ringed dragonfly (Cordulegaster boltonii – a species with an unusually long ovipositor).[3]
The generic name Anax is from the ancient Greek Greek, Ancient (to 1453);: ἄναξ, "lord";[4] the specific epithet imperator is the Latin for "emperor", from imperare, to command.[5]
This dragonfly has a wide distribution; it is found throughout Africa and through most of Europe, the Arabian Peninsula, and south-western and central Asia. Since the 1990s, its range has expanded in Europe, both northwards and to higher altitudes. For example, the first Scandinavian record was in 1994 in Denmark; in 2002 it was first recorded in Sweden and in 2004 first in Scotland; today it is regular in all three countries.[1] [6]
The emperor dragonfly is a large and bulky species. It is long, with average being and males growing larger than females.[1] [7] The average wingspan is .[7] When they first emerge, both sexes appear pale green with brown markings. The legs are brown with a yellow like base. Wings are born black but grow yellow-brown when they grow. Males have a sky blue abdomen marked with a diagnostic black dorsal stripe and an apple green thorax. The thorax and head of a male is green and their prominent eyes are blue. Females have similar markings but they are mainly green.
They frequently fly high up into the sky in search of prey, which includes butterflies, other Odonata and tadpoles; small prey is eaten while flying. They breed in a variety of aquatic habitats from large ponds to dikes, but they require a plentiful supply of vegetation in the water. The females lay the eggs into plants such as pondweed, and always lay alone. The larvae are very aggressive and are likely to influence the native species composition of colonized freshwater ecosystems. The adult male is highly territorial, and difficult to approach.[8] In the summer months emperor dragonflies are frequent visitors to gardens, being especially prevalent in the southern counties of Great Britain.