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