Emperor Dragonfly

Anax imperator

This "Ruler of the Skies" above our waters is one of the largest among native dragonflies. On warm sunny days, the conspicuous males are usually on the wing and can fly for hours at a time. Within the National Park, the Emperor Dragonfly may be spotted more frequently in the Lobau than in other areas, where it is rarer.

Description
Body length of around 8cm and a wingspan of 11cm. The male has a blue abdomen with a black stripe running the length and like the female, a green thorax. The female abdomen is more blue-green with a somewhat wider brown dorsal stripe.

Distribution
The range encompasses the southern portions of Asia and Europe as well as parts of Africa. In the National Park, Anax imperator may be observed on most vegetation-rich backwaters.

Endangerment and Conservation Status
Listed as "least concern" in Europe and Lower Austria. May be commonly seen in the Lobau area, but not as often in other areas of the National Park.

Behaviour
On warm days, the males can be observed flying above the water for hours on end. Because males are highly territorial, there are normally few dragonflies on any given body of water. Male hawkers – hawkers being those dragonflies who spend most of the time in the air – will often engage in fierce air battles and boisterous chases. Unlike the Lesser Emperor, the female Anax imperator lays its eggs, usually on floating vegetation, without the companionship of the male. Depending on the water temperature, larvae may over-winter not just once, but twice. Eclosion takes place in alluvial vegetation; often, in each body of water, all larvae may undergo their incomplete metamorphosis almost simultaneously.

Special Characteristics
Normally, larvae in any given body of water develop nearly simultaneously to their final or imaginal moult. The final moult usually takes place during the night, often high up in trees.