Altinote dicaeus callianira - it's distinct pattern advertises it's unpalatability to avian predators

Aposematic colouration is a term used to describe colours and / or patterns that act as a warning to predators that a potential prey species is unpalatable, toxic or dangerous.

Various studies have shown that all vertebrates including insectivorous birds associate greens and blues with safety, and inherently regard red, orange, yellow and white as signs of danger. It is also widely accepted that patterns incorporating stripes or spots draw attention to objects. Consequently it is no surprise to find that toxic or unpalatable butterflies have evolved colour schemes that reflect these facts, in order to "label" themselves as being unpleasant to eat, and thereby dissuade birds from attacking them. Equally it is unsurprising that a significant number of palatable species have evolved which mimic the patterns of toxic species, in order to trick birds into leaving them alone.

Birds can remember the colours and patterns of butterflies, and associate them with pleasurable or unpleasant experiences. If a bird pecks at a toxic butterfly it finds the taste very unpleasant, and is likely to suffer consequences including vomiting, nausea and visual disturbance. Experiments with various insectivorous birds have shown that if they suffer this experience they then avoid eating similarly coloured butterflies for several hours or days. Periodically they re-sample aposematically coloured butterflies, thereby reaffirming their unpalatability.

Diematic patterns

Often the frightening effect of diematic markings is only temporary. Having gotten over the initial shock a bird may resume it's attack. In such circumstances the ocelli on the butterfly's wings take on a secondary defence role, diverting and confusing the predator :

When a bird attacks a butterfly it naturally focuses it's aim on an obvious target area. The presence of a decoy target such as a false eye diverts the attack away from the butterfly's body, towards the wing borders. Usually this results in nothing more than a small chunk being pecked out of the wing, and the insect escapes virtually unharmed. It is not unusual to find ocelli-marked butterflies which have had chunks pecked out of their wings by birds. Butterflies are able to fly and go about their lives with quite large pieces missing from their wings, but an attack on their body would be fatal.

The Zebra Teaser Arawacus separata and many other butterflies in the subfamily Theclinae have wings that are marked with bright streaks which lead the eye away from their head, and towards antennae-like tails on their hindwings. In many species there is also a red or black spot near the tail, which simulates an eye.

Large groups of males gather to feed on mineralised moisture on riverbanks. They bask when feeding, displaying their metallic blue uppersides, which help other passing males to locate them and home in on the feeding grounds.

A group of butterflies on the ground could easily be attacked by birds however, so the butterflies need to employ a defence strategy. Any kind of minor disturbance causes one or two butterflies to get twitchy, at which point they start fanning their wings nervously so that the bright red undersides are visible to the other butterflies.