Most research on aposematism has focused on chemically defended prey, but the signalling difficulty of capture remains poorly explored. Similar to classical Batesian and Müllerian mimicry related to distastefulness, such ‘evasive aposematism' may also lead to convergence in warning colours, known as evasive mimicry. A prime candidate group for evasive mimicry are Adelpha butterflies, which are agile insects and show remarkable colour pattern convergence. We tested the ability of naive blue tits to learn to avoid and generalize Adelpha wing patterns associated with the difficulty of capture and compared their response to that of birds that learned to associate the same wing patterns with distastefulness. Birds learned to avoid all wing patterns tested and generalized their aversion to other prey to some extent, but learning was faster with evasive prey compared to distasteful prey. Our results on generalization agree with longstanding observations of striking convergence in wing colour patterns among Adelpha species, since, in our experiments, perfect mimics of evasive and distasteful models were always protected during generalization and suffered the lowest attack rate. Moreover, generalization on evasive prey was broader compared to that on distasteful prey. Our results suggest that being hard to catch may deter predators at least as effectively as distastefulness. This study provides empirical evidence for evasive mimicry, a potentially widespread but poorly understood form of morphological convergence driven by predator selection.

19Most research on aposematism has focused on chemically defended prey, but 20 signalling difficulty of capture remains poorly explored. Similarly to classical 21 Batesian and Müllerian mimicry related to distastefulness, such "evasive 22 aposematism" may also lead to convergence in warning colours, known as 23 evasive mimicry. A prime candidate group for evasive mimicry are Adelpha 24 butterflies, which are agile insects and show remarkable colour pattern 25 convergence. We tested the ability of naïve blue tits to learn to avoid and 26 generalise Adelpha wing patterns associated with difficulty of capture, and 27 compared their response to that of birds that learned to associate the same wing 28 patterns with distastefulness. Birds learned to avoid all wing patterns tested, but 29 learning was faster with evasive prey compared with distasteful prey. Birds 30 generalised their learned avoidance from evasive models to imperfect mimics if 31 the mimic shared colours with the model. Despite imperfect mimics gaining 32 protection from bird's generalisation, perfect mimics always had the best fitness, 33 supporting selection for accurate mimicry. Faster avoidance learning and broader 34 generalisation of evasive prey suggest that being hard to catch may deter 35 predators at least as effectively as distastefulness. Our results provide empirical 36 evidence for a potentially widespread alternative scenario, evasive mimicry, for 37 the evolution of similar aposematic colour patterns. 38 KEYWORDS 39 Adelpha -evasive aposematism -predator learning -distastefulness -40 convergence -prey defence 41 42