Visually similar species might use odours and sounds for identification. But just because two species look the same to our eyes – or more importantly, to a predator’s – they can appear very different to each other.
Take the remarkably similar wing patterns of tropical American Heliconius and Eueides butterflies.
Mutual mimicry between these toxic insects boosts the deterrent power of their warning pattern, much like bees and wasps have converged on yellow and black stripes.
But while the yellow patches on the wings of Heliconius reflect UV light – which is not visible to their vertebrate predators – those of Eueides do not.
This subtle yet significant difference provides a private channel of visual communication that prevents mistaken identity during courtship.