Anax parthenope | Lesser Emperor

The Lesser Emperor

A blue saddle over the pond

This dragonfly patrols ponds and canals. A male carries a blue saddle near the tail base. Its body stays brown elsewhere.

Eyes glow blue green. Females wear dull yellow brown instead. Wings stretch 40 mm to 47 mm.

Because males defend a patch of water, fights break out all summer. Adults fly from May to September. Though the insect is smaller than the emperor dragonfly, it holds a territory just as fiercely and often wins against larger rivals.

Family tree

Aeshnidae, the hawkers

This insect belongs to the dragonfly family, Aeshnidae. Its genus name is Greek for lord. De Selys described the species in 1839. A Greek siren gave the species its name.

Two other Anax species live in Europe. One of them crossed the Atlantic long ago. The Common Green Darner is that American cousin. Both hunt on the wing, though the styles differ.

Both migrate when the weather turns. Because the family is so old and the species look alike in the hand, field workers rely on saddle colour rather than on the wings to tell them apart.

52 mm of brown and blue

How to tell one

Its abdomen runs 46 mm to 52 mm. Hindwings reach 47 mm. A male shows blue on the second segment. That patch is called a saddle.

Eyes hold tens of thousands of lenses. Each lens sees a small part of the world. The brain joins the pieces into one wide view, yet it reacts in a fraction of a second. Legs form a basket for catching prey.

Spines on the legs stop insects slipping out, though prey is often eaten in mid air. Four wings beat out of step with each other. Because the wings work independently, the insect can hover, reverse and turn in its own length, which few birds manage.

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Warm ponds and slow canals

Where it lives

Still water is the main home. Ponds, lakes and canals all work. Gravel pits and reservoirs also fill up with them. Floating plants help the larvae, since they hide from fish.

Warm, sunny sites hold the most. Its range covers southern and central Europe. North Africa and the Middle East also have them. The species has pushed north for 30 years.

Warmer summers, however, opened new ponds. Although the insect can use a garden pond, it needs water that holds fish free shallows and plenty of plant cover for the larvae.

Insects caught in flight

What it eats

Both stages are hunters. Adults take flying insects on the wing. Midges, flies and moths are common prey, though anything airborne will do. Smaller dragonflies are caught too.

A hunt lasts a few seconds. The basket of legs closes around the target, while the jaws finish the job. Larvae hunt underwater with a hinged jaw. That jaw shoots out in a fraction of a second.

Tadpoles and insect larvae are taken. Since the larva needs two years to grow, a pond must hold food through several seasons before it produces an adult.

Eggs laid in plant stems

The breeding cycle

A male holds a stretch of bank. He hovers low over the water. Rivals are chased away at once, though a few always return. Females fly in to lay eggs.

She pushes them into floating plants. He guards her while she works. Eggs hatch after about 3 weeks. A larva moults 10 times or more.

Two years pass before it crawls out. Adults then live only 6 or 8 weeks.

Least Concern

Conservation

The IUCN calls this dragonfly Least Concern. That assessment dates from 2015. Numbers, however, look stable or rising. Drainage of ponds is a local threat.

Pollution kills the larvae. Fish stocked for anglers eat them. Warmer summers help in the north. Drought, though, hurts in the south.

Garden ponds now matter a great deal. Because the species breeds in small, warm water bodies, thousands of back garden ponds have quietly replaced the farmland pools that drainage destroyed.

Side by side

How It Compares

Common misreadings

What People Get Wrong

• A blue saddle means emperor. Emperors stay blue all along.
• Dragonflies can sting people. They carry no sting at all.
• All dragonflies die before winter. Some cross the sea.

Going further

Sources and Further Reading

• IUCN Red List entry for Anax parthenope
• Wikipedia, Anax parthenope
• Dijkstra, K.-D. B. and Lewington, R. Field Guide to the Dragonflies of Britain and Europe.
• British Dragonfly Society. Species account for Anax parthenope.

Quick hits

Five things to remember

• A male carries a blue saddle.
• Its genus name means lord.
• It crossed into Britain in the 1990s.
• The larva spends two years in water.
• It can hover, reverse and turn on the spot.