Emperor / Blue Emperor (Anax imperator) La libélula emperador

Emperor / Blue Emperor (Anax imperator) La libélula emperador

  • Family: Aeshnidae
  • Scientific name: Anax imperator Leach, 1815
  • English common name: Emperor or Blue Emperor
  • Spanish common name: La libélula emperador
  • Portuguese common name: Libelinha (not sure of common name)

One of the largest resident dragonflies on the Iberian Peninsula. The Emperor / Blue Emperor (Anax imperator) La libélula emperador is both fast flying and highly territorial and as such is seldom seen at rest. A large pond or stretch of river may only support one male who will tirelessly patrol his patch of water, promptly seeing off any intruders with a fierce clash of wings.

Emperor / Blue Emperor (Anax imperator) La libélula emperador
Emperor / Blue Emperor (Anax imperator) La libélula emperador – Male
Details
  • Total length: 66 to 84mm
  • Hind Wing length: 42 to 52mm
  • Altitude: Sea level to 1500m+
  • Flight period in Iberia: late April to late October
  • Habitat: Open water with plentiful emergent vegetation around ponds, rivers & lakes.
  • Distribution: Europe, Western Asia, Africa & the Middle East. Widely distributed throughout the Iberian Peninsula.
  • Similar species: Lesser Emperor – Anax parthenope & Green Darner – Anax junius (a very rare migrant from North America first recorded in 1998).
Description

The male has a strikingly blue abdomen which when in flight has a slightly downward curve, giving a bent appearance, a useful feature for separating the restless Emperor from the other hawker type dragonflies whose abdomens generally appear straight. The blue green eyes & green thorax make this a very handsome insect.

The female is generally green in appearance with dark markings along the centre of the abdomen. They oviposit alone into floating vegetation or submerged plant stems, a feature which helps to separate this species from the Lesser Emperor – Anax parthenope which generally oviposits in tandem.

Emperor / Blue Emperor (Anax imperator) La libélula emperador
Emperor / Blue Emperor (Anax imperator) La libélula emperador – Female laying eggs or ovipositing
The larval stage
Emperor / Blue Emperor (Anax imperator) La libélula emperador
Emperor / Blue Emperor (Anax imperator) La libélula emperador – Exuvia or shed nymph exoskeleton

The larval stage of the Emperor may last from one to two years before emerging as an adult on reeds or rushes around the margins of their chosen water body. The cast skin or exuvia can be found long after this spectacular transformation takes place and is an exact replica of the larvae which can be identified to species level. Collecting these exuviae can give an excellent indication of the true population size at a site and is conclusive proof of successful breeding.

Article credits
  • Thanks to Steve Jones for the images and excellent, informative text in this article.
  • Top image: Female blue emperor by Charles J. Sharp – Own work, from Sharp Photography, sharpphotography, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=42045065
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