The young Erythrinus erythrinus mimics the colour pattern of the female of its specific prey, the cyprinodont fish Rivulus agilae. The male Rivulus is attracted by the predator, and, when performing sexual display in front of it, is caught by the tail and swallowed. Various experiments in captivity confirm the constancy of this behavioural pattern.
The morphological, ecological and behavioural specializations related to the aggressive mimicry by Erythrinus are described. The colour pattern of the young Erythrinus disappears completely when the fish becomes subadult and leaves the highly specialized habitat of the Rivulus, to settle in deeper water. Comparisons between the present case and other described cases of aggressive mimicry are made. The evolutionary processes involved in aggressive mimicry displayed by Erythrinus are examined: origin of the morphological adaptations in the predator, consequences for the population dynamics in the prey.