Butterfly wing patterns in flight create powerful illusory motion cues

The dazzling stripes found on zebras and snakes have long been thought to interfere with predator motion perception^1,2, but this hypothesis has received little empirical support so far³. Butterflies show enormously diverse and high-contrast wing patterns, the function of which has inspired intense theoretical debate and research⁴. Here we suggest that butterfly wing patterns work in tandem with flight dynamics to create visual illusions that confuse predators. We use multiple lines of enquiry with biologically inspired modelling to support this hypothesis: free-flight butterfly take-offs filmed at high speed demonstrate the creation of misleading motion cues; phylogenetically controlled analyses demonstrate that this is an evolutionarily widespread strategy; in silico evolution experiments independently converge on high-contrast butterfly-like wing patterns; and behavioural experiments validate model predictions. Our results show that butterfly wing patterns and flight dynamics create powerful illusory motion effects, potentially representing one of the most successful visual defence strategies in moving animals.