Aposematism
Aposematism is warning coloration in toxic or unpalatable butterflies. Bright colors signal danger to predators and protect the species from being eaten.
Definition
Aposematism (from Greek apo — away, sema — sign) is an evolutionary strategy in which an animal shows a predator a signal of danger through bright coloration, characteristic odor, sound, or behavior.
In butterflies, aposematism appears mainly as bright contrasting coloration — red, orange, or yellow combined with black.
How aposematism works
- The butterfly is toxic or unpalatable (because of toxins accumulated from its host plant)
- Its bright coloration makes it conspicuous — it does not hide but attracts attention
- A predator (bird, lizard) tries such a butterfly and remembers the unpleasant experience
- Next time the predator avoids butterflies with a similar appearance
This benefits all members of the species: the predator generalizes the experience to the whole “pattern,” and even butterflies that were not touched are protected.
Aposematism and mimicry
Aposematism often goes hand in hand with mimicry: edible species evolutionarily copy the coloration of aposematic ones, exploiting the “reputation” of toxic species.
Examples
| Species | Toxin | Coloration |
|---|---|---|
| Monarch (Danaus plexippus) | Cardenolides from milkweed | Orange + black |
| Heliconiines (Heliconius spp.) | Cyanogenic glycosides | Red + yellow |
| Russian tiger moth (Callimorpha) | Pyrrolizidine alkaloids | Red + black |
More on wing coloration — in the article why butterflies have bright wings.