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Lesser Purple Emperor Butterfly - Apatura ilia

Phylum: Arthropoda - Class: Insecta - Order: Lepidoptera - Family: Nymphalidae

Lesser Purple Emperor Butterfly - Apatura ilia

We saw our first Lesser Purple Emperor butterfly in northern Italy many years ago, and we are still waiting and hoping to come across a second specimen! These lovely butterflies, which come in two colour forms, are not a common sight, partly because of their shyness and habit of spending most of the day high up in trees; however, the males are attracted towards human perspiration, and sometimes they congregate to drink from moist animal dung.

Lesser Purple Emperor attracted to a perspiring hand

Above: Apatura ilia form ilia attracted to perspiration on a human hand.

Apatura ilia form 88 attracted to perspiration on a human hand

Above: Lesser Purple Emperor form clytie is also attracted to human perspiration.

Description

With a wingspan of 6.5 to 7.5cm, this beautiful butterfly and its close relative the Purple Emperor are able to display iridescent blue-purple hues, dependent on the directions of incident and reflected light. Unlike chemical pigments, the emperor's wings are studded with strongly reflecting iridescent scales that diffract light, and this results in a narrow-frequency-band reflected spectrum that is visible only in a narrow angular range.

The wings have either a black background (form ilia) or a dark brown background (form clytie), and in males the wings display a blue-purple iridescence when viewed from a particular angle. On the forewing leading edge there are two groups of white spots, and there is a large orange eye with a black centre in the middle of wing with two more large white spots nearby. The underside of the forewing is light brown with two pairs of black spots near the leading edge and close to the body, while the white spots from the upperside are also present in the corresponding underside locations. At the margin of both forewing and hindwing there is a chain of grey spots on the uppersides, not replicated on the undersides.

In the middle of hindwing, which is more deeply scalloped than the forewing, there is a long white band, while on the upperside towards the trailing edge a single light-brown ring is not replicated on the underside. The body is greyish and almost black on top.

Lesser Purple Emperor - Apatura ilia, showing no iridescence

Females of both forms are very similar to the males but have no blue-purple iridescence. Females of form ilia, with black wing backgrounds, can be distinguished from Southern White Admirals by the presence of the orange-ringed eyespot on their hindwings.

In hot weather these butterflies spend most of the time high up in the tree canopy, making photography almost impossible; however, they do sometimes come down and congregate to drink water from patches of damp riverside sand and moist animal excrement.

Lesser Purple Emperor - Apatura ilia, underside of closed wings

As seen in the picture above, Lesser Purple Emperors sometimes feed on sap emerging from damaged bark of their larval host plants.

Distribution

This lovely butterfly is not native to Britain and is not known to come in as a vagrant. Its range on mainland Europe includes northern Portugal, Northern Spain, France, southern Germany and across northern Italy to the Balkans and Greece. It is absent from southern Italy and the Mediterranean islands.

Habitat

This is a butterfly of broad-leaved woods and forests, where it can bee seen in clearings and along tracks that are bordered by willows and poplars. Lesser Purple Emperors also occur in wooded valleys, where they are attracted to riverbanks that are lined by willows.

Lesser Purple Emperor - Apatura ilia, France

Lifecycle

Depending on location, the Lesser Purple Emperor is either univoltine and seen on the wing between late May and July, or bivoltine and seen on the wing between June and early September. The larval food plants are various poplars and willows, notably Populus tremula, Populus alba and Populus nigra as well as Salix alba and Salix caprea. The females lay their eggs singly on the uppersides of the leaves of host trees, and this species overwinters as young larvae.

Studying butterflies and moths...

Acknowledgements

This page includes pictures kindly contributed by Steve Jelf.

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