Meet The Carnivorous Emperor Butterfly

The Emperor butterfly, also known as Apatura iris, lives in some parts of England and is unique for its striking blue color and strange eating habits: they eat carrion and dung. If you want to lure it and take a photo, bring something foul-smelling as bait.

Emperor Butterfly Species Summary

Scientific NameApatura iris
Family NameNymphalidae
HabitatDense woodlands
RangeCentral and Southern England
Host PlantsSallow
Butterfly DescriptionThe upper side of their wings is black and blue with a gray, brown, and white underside
Caterpillar DescriptionGreen with white and yellow markings

Butterfly Physical Description

Male's underside
Male’s underside

The Purple emperor butterfly belongs to the order Lepidoptera, family Nymphalidae, and is a unique, iridescent blue butterfly. The butterfly wings of males are bright, while females have paler upperside. Males also have a slight tinge of green on the dorsal side of their wings.

Both sexes have a tiny orange-white patch close to the forewings and a band of white spots across both wings. Their undersides are paler and lack silvery iridescence. Females are a bit larger than males. Females resemble the White admiral, only with the orange eyespot on its hindwings. The wingspan of this butterfly ranges from 2 3/16 to 2 11/16 inches.

The pupa stage (chrysalis) is striking, and even the most experienced butterfly enthusiasts may mistake it for the host plant’s leaf. Therefore, this is one of the best examples of camouflage in nature.

Emperor Butterfly Compared to similar species

Some blue and black butterflies are similar to the Emperor. Here’s a brief comparison:

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Blue swallowtailRecognizable for the “tails” on their wings and orange spots on the undersides of hindwings
Lesser purple EmperorStrikingly blue, with white spots and brownish edges all around its wings
Blue morphoBlue, without the white spots, but with black edges all around
Sara longwingBlack and blue, with long wings and prominent white areas
Blackened bluewingMore muted blues, closer to the butterfly’s body

Why are they called Emperor Butterflies?

This butterfly is also often referred to as His Imperial Majesty, likely because of its beauty. Additionally, Apatura (Greek) is a word related to deception, referring to male wings which are iridescent only under a certain angle.

Caterpillar Physical Description

Emperor's caterpillar
Emperor’s caterpillar

The Purple emperor’s larvae (caterpillars) are green with white and yellow markings. They have two “horns” at their anterior and one smaller at the posterior. Once they hatch, they’ll rest on the leaf’s midrib to match the environment. During winter, the larvae will hibernate on sallow branches. It will also change its color from green to brown to camouflage on dry branches.

What is the lifespan of an emperor butterfly?

Egg Stage10 days
Caterpillar Stage14 to 28 days
Chrysalis Stage7 to 14 days
Butterfly Stage30 to 120 days

Purple Emperor’s Habitat

The Emperor butterfly prefers dense, broadleaved woodlands, tropical and subtropical forests, and clusters of smaller woods. It also frequents areas with a good supply of willow.

Usual Host Plants

The host plant is usually sallow, but this butterfly may visit tree and shrub celtis in the elm family (Ulmaceae). It lays eggs on various trees, from medium-sized shrubs to tall canopies. If you want these pretty butterflies around in your garden, plant sallow or trees that produce sap.

Strange feeding habits of Emperor butterfly

These shiny blue butterflies feed on carrion, dung, and even urine. When it comes to plants, they’ll eat goat willow (Salix caprea) and honeydew secreted by aphids (not flower nectar). In some cases, they’ll eat tree sap oozing from oak trees.

Why Do Emperor Butterflies Eat Carrion?

It might look strange to see a butterfly on a carrion. However, these butterflies eat it to obtain the required salts and minerals for reproduction.


Besides their strange eating habit, the male Emperors will perch in full sun, looking for females. They fly high and are hard to spot. Since they share their space with the birds, they tend to be violent and attack species like buzzards. Those who wish to see one of the Purple emperors should bring binoculars and something rotting.

Common Predators

The most common predators of the Purple emperors are bats, frogs, and birds. Luckily, the caterpillar is very well camouflaged among leaves.

Are Emperor Butterflies Poisonous?

So far, there are no mentions of the Purple emperor’s toxicity for predators or people.

Where do emperor butterflies live?

This butterfly species was present in most of England, but today it’s only located in central-southern England. Other locations where you may see some strays include Bolivia and the lower Rio Grande Valley (Texas and Mexico).

Are Emperor Butterflies Endangered?

By the 1960s, the Emperor’s population was relatively scarce in their regular regions. Even though its numbers are still declining, the Purple emperor is not considered fully endangered. Today, they’re assigned a medium butterfly conservation priority.

Do Emperor Butterflies Migrate?

This butterfly’s population is confined to a small area, mainly in southern England. It doesn’t migrate, although some hope it will start to expand into suburban areas.

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