Mnais costalis 3 3 exist in 2 forms specialised for the demands of 2 distinct strategies, territorial fighters and non-territorial sneaks, which give approximately equal fitness payoffs. Territorial 3 6 have orange wings, whereas typical non-territorial 3 3 are clear-winged. By simulating agonistic encounters between 3 3 it is shown that the 2 morphs showed distinct responses to the signal from orange wings; territorial orange-winged 3 <5 always tried to enter contests, while clear-winged 3 3 always avoided them. On the other hand, the 2 morphs showed similar responses to the signal from clear wings: both morphs tried to attack models. Also presented are ‘painted clear models’ which were clear-winged 3 3 whose wings had been painted orange, and both morphs responded as if they were orange-winged models. These observations indicate that 3 3 discriminate between fighter and sneaker morphs using the colour of wings, and shows different styles of agonistic responses toward fighter and sneaker morphs. It is likely that non-territorial sneaks may gain an advantage from non-signalling because clear wings increase crypsis on another 3 territory, increasing their success in stealing copulations. No indication was found that clear-winged 3 3 are 9 mimics, or that having clear wings reduced the level of aggression directed towards them by territorial orange-winged 3 3.