Predation:

Aposematism, where organisms are brightly colored as a warning to predators, is the antithesis of camouflage. Some organisms pose a threat to their predators—for example they may be poisonous, or able to harm them physically. Aposematic coloring involves bright, easily recognizable and unique colors and patterns. For example, bright coloration in Variable Checkerspot butterflies leads to decreased predation attempts by avian predators. Upon being harmed (e.g., stung) by their prey, the appearance in such an organism will be remembered as something to avoid. While that particular prey organism may be killed, the coloring benefits the prey species as a whole.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". What do predators use to warn their prey?
unanswerable