Many insects are chemically defended and toxic to predators. Whilst some species avoid detection, so-called 'aposematic' insects use conspicuous colour pattems to advertise their toxins to potential predators. Although the initial evolution of aposematism is often considered a paradox due to the increased detection risk associated with conspicuousness, the role of learned avoidance and memory in naive predators is widely described as the major driving force. However, many insects have extemally detectable defences, and may be taste-rejected by predators. This role of taste-rejection has been largely overlooked, but could offer support for the theory of the evolution of aposematism by individual selection.