Overview

Brief Summary

Biology

Dragonflies undergo a type of development known as incomplete metamorphosis in which the aquatic larvae (sometime called nymphs) undergo a series of moults; the stages between moults are known as instars or 'stadia' (4). After hatching from eggs, the larvae develop quickly through the summer; they enter their final instar during the autumn of the following year, and then enter 'diapause', a form of hibernation, before emerging as adults early the next summer (2). In the first few instars, the larvae swim by undulating the body from side-to-side; later on they develop a system of jet-propulsion which enables them to easily escape from predators such as water bugs, fish, other dragonfly larvae and beetles. The larvae of the emperor dragonfly are themselves voracious predators, armed with fearsome mouthparts known as a 'mask'; the mask is normally tucked under the head, but is rapidly extended in under 25 milliseconds (4), piercing prey as large as small fish (2). After diapause, final instar larvae leave the water and crawl up vegetation. The adult emerges, leaving the discarded skin of the nymph attached to the plant (5). The new adults undergo a period of feeding and maturation before starting to reproduce (4). Males set up territories, which they defend fiercely against other males; they fly rapidly at two to six meters over the water, and very rarely come to a rest. During mating, males and females form a typical 'wheel' mating posture, in which the male grabs the female behind her head using the claspers at the tip of his abdomen. After mating the female lays her eggs in floating vegetation, keeping low to avoid encounters with territorial males (2).
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Description

The emperor is Britain's largest dragonfly; they are a spectacular sight with their broad wings and powerful flight. After emerging, both sexes are pale green with brownish markings. The legs are brown, becoming yellowish towards the base; the wings have black veins, and take on a yellowish-brown tinge with age. Males develop a bright blue abdomen with a black 'fish-bone' line passing down the centre; the thorax and head are green and the prominent eyes are blue. Females have similar markings to males, but are mainly green in colour, becoming brownish on the last few segments of the abdomen. Both sexes possess appendages at the tip of the abdomen known as 'claspers', which are used in mating; in males these claspers are more robust than in females (2). The larvae or 'nymphs' are brownish in colour and have stocky bodies with rounded heads that feature very large eyes (3).
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Distribution

Range Description

Anax imperator is known from the whole Africa to most of Europe, the Arabian Peninsula and southwest and Central Asia. Within India it is present in West Bengal (Kolkata district), Uttarakhand, Maharashtra and Tamil Nadu. The species is presently expanding to the north due to the global warming and has been found in the southern part of Sweden up to Uppsala. In the British Isles, its northern limit shifted by 80 km to the north so that now the species is known from Scotland.
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Range

This dragonfly has a broad global distribution; it is found in Europe from Portugal to Germany in the north, and extends eastwards to central Asia (1). It is also known from North Africa and the Middle East (2). In Britain, it is fairly widespread in southern England and south Wales, but becomes quite scarce in the north Midlands, although there are signs that the species is currently extending northwards (1).
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
Anax imperator breeds in any kind of standing and slow running waters bordered with rushes and weeds. It is a familiar species on all open waters, where males patrol and hawk restless over their territory and exclude their congeners. Males most generally don't accompany the female during oviposition.

Systems
  • Terrestrial
  • Freshwater
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Breeds in a range of aquatic habitats including large ponds, canals, slow-flowing rivers, lakes, flooded gravel pits, and dykes, but in all cases there must be a plentiful supply of marginal vegetation that emerges from the water (1).
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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Anax imperator

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 7
Species With Barcodes: 1
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2013

Assessor/s
Mitra, A.

Reviewer/s
Kakkasery, F., Babu, R., Mondal, S., Brooks, E., Clausnitzer, V., Dow, R.A. & García, N.

Contributor/s
Boudot, J.-P., Samraoui, B. & Schneider, W.

Justification
Anax imperator is a widespread species with no major threat worldwide and it is therefore assessed as Least Concern.

History
  • 2010
    Least Concern
  • 2006
    Least Concern
    (IUCN 2006)
  • 2006
    Least Concern
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Status

Common and widespread (3).
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Population

Population
The species is generally common and shows often large populations.

Population Trend
Stable
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Threats

Major Threats
Anax imperator is not threatened at the global scale, although local declines may occur due to habitat destruction and water pollution.
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This species is not threatened at present, however many dragonflies are vulnerable to water pollution and loss of habitat by infilling of ponds, and drainage of water bodies (4).
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Management

Conservation Actions

Conservation Actions
This is a widespread species, and specific conservation measures are not needed.
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Conservation

The profile of dragonflies has been raised in recent years, and many landowners build ponds in order to encourage them (4). The British Dragonfly Society aims 'to promote and encourage the study and conservation of dragonflies and their natural habitats, especially in the United Kingdom' (6).
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Wikipedia

Emperor (dragonfly)

The Emperor Dragonfly[2] or Blue Emperor[1] (Anax imperator) is a large species of hawker dragonfly of the family Aeshnidae, averaging 78 millimetres (3.1 in) in length.[2] It is found mainly in Europe and nearby Africa and Asia.

Behaviour[edit]

Male in side view
In flight

They frequently fly high up into the sky in search of prey, which includes butterflies, Four-spotted Chasers and tadpoles; small prey is eaten while flying. They breed in a variety of aquatic habitats from large ponds to dykes, 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 male is highly territorial, and difficult to approach.[3]

Identification[edit]

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 with age. 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.[3]

References[edit]

  1. ^ a b Clausnitzer, V. (2006). "Anax imperator". IUCN Red List of Threatened Species. Version 2010.1. International Union for Conservation of Nature. Retrieved 2010-06-10. 
  2. ^ a b "Emperor". British Dragonfly Society. Retrieved 25 August 2010. 
  3. ^ a b "Emperor dragonfly videos, photos and facts — Anax imperator". ARKive. Retrieved 2013-08-08. 
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