Length around 71mm, the Lesser Emperor is a larger insect, the blue band extends down the sides of the abdomen, the eyes are green (as opposed to brown) and the abdomen is predominantly greenish-brown (as opposed to yellow-brown in the Vagrant). Male Lesser Emperors also have a waisted abdomen. Females are similar to males but usually duller, lacking males pinched waist and having brownish, rather than green eyes.

A. parthenope is smaller and less colourful than its relative but much more common the Anax imperator (Emperor Dragonfly). In general appearance, especially when seen on the wing, A. parthenope is similar to A. imperator but A. parthenope tends to hold its abdomen straighter than A. imperator. A large dragonfly seen in flight with a bent abdomen is most likely to be A. imperator rather than A. parthenope. A. parthenope has a very noticeable blue saddle at S2 and S3 which can be seen in flight which is in contrast to the rest of the abdomen which is brown. There is a yellow rin at the base of S2. The eyes are green. It is similar to A. ephippiger although A. ephippiger is slightly smaller and slenderer and its blue saddle does not wrap around S2 but is mostly blue on top. A. ephippiger has brown eyes.

This rare vagrant is also likely to be confused with Migrant or Southern Hawker. It is immediately told from hawkers by the lack of black markings on the thorax. The most striking feature is a pale blue band around abdominal segments 1 & 2, contrasting with the rest of the largely plain brownish abdomen. 

Breeds in ponds and small lakes and can tolerate brackish water. 

Like the Blue and Vagrant Emperors, the Lesser Emperor has been extending its range Northwards. It's now a fairly common sight as far North as the Netherlands, even though its European home is still in the Mediterranean basin. 

In the south of its range A. parthenope can be on the wing in March. It is most commonly seen from June to September but can still be around in November. Often seen patrolling around ponds, lakes and other still water. Where it occurs with A. imperator it is usually less abundant. When A. parthenope and A. imperator occur at the same ponds A. imperator is dominant. Male and females mate in the normal dragonfly manner and after mating the pair stay in tandem and egg-laying usually occurs whilst still in tandem. This behaviour not seen in other European hawkers with the exception of Aeshna affinis, although two migrants to Europe, A. ephippiger and A. junius also oviposit in tandem. Eggs are inserted into plants or in mud and hatch out in two months. Larval development takes two years.