Caterpillar of Purple Emperor, iris (Apatura iris)
Also Called"Sherif Longhorn"  
Christian Kock og Jens Stolt
Pinseskoven, Vestamager, DK. 19. juni 2006, feeding on Salix cineria hybrid.
Caterpillar in resting position.
Frontal view of caterpillar.


Sideview of larva on salix branch.

Caterpillar eating Salix cineria. Small Hemiptera nymph in front.
Camouflage colours and behavior on leaf of sallow. .

Picture 1

The Apatura iris caterpillar can display aggressive as well as inconspicuous behaviour. When it is disturbed by vibrations in the branches it immediately stiffens and presses its head and horns to the leaf's surface to resemble a leaf.
When the caterpillar is disturbed by small insects it comes after them with the horns. We saw it give a cast of its head and use the the horns to scare away a Hemiptera nymph. This behaviour might also be effective towards parasitic wasps.

B: When the caterpillar is resting on the leaf it bends the horns down and touches the leaf with the tip while it raises the first part of the body. This behaviour makes light shine under the caterpillar and makes it resemble a hanging leaf.

A: Two horns means that no matter which angel the caterpillar is viewed from, it will always present a "stalk". The horns are darker on the ventral side that leans towards the leaf. This gives the impression of a round shape, a stalk.
From the dorsal side the light colour that continues to the back of the caterpillar resembles the ribs of the sallow leaf. When the caterpillar raises its head the bluish colours of the ventral side of the horns appear and it suddenly looks scary or poisonous.

D: The green body of the caterpillar is darker on the dorsal side. This means counter shadow, like in many mammals, and makes the body appear flat like a leaf.

C: The rear of the caterpillar resembles the tip of a sallow leaf very well

Caterpillar displaying threathening behavior towards Hemiptera nymph.

Picture 2

A frontal view on the Apatura iris caterpillar shows us some different features:
Y: The grey blue stripes is now a warning as they appear very clear on the darker shades on the ventral side of the horns. The grey blue stripes continue beside the eyes, break the outline of the head and eyes and bring the horns in focus. It looks weird like nothing else in European wildlife. I cannot explain the meaning of this.

X: The end of the horn is redish and bend forward, to mimicry a snails eye, I suppose.

Z: Light grey stripes on the back protrude from the horns and accentuates them from a frontal view.

The Apatura iris caterpillar is rather energic when moving around, it moves fast and like imago it also appears to be aggressive. It confronts small creatures in the vegetation and use the horns to "bully" them.

Photo of imago
Newly hatched Male Purple Emperor at the Bait.
Female Purple Emperor
Male underside
Frontal view of horns. Note colour at end.
Camouflage behavior. Note woven silk on leaf.
Close up of silk on leaf.
Chrysalis of Purple Emperor