Fig. 1. Top view of Y-maze apparatus. The height of the Y-maze is 45 cm. The training and decision areas can be separated by inserting a removable board between two areas (arrow). The floor and the end walls of the two arms were covered with black plastic sheet. The other walls and the ceiling were covered with a 3 mm mesh plastic net. The tested butterflies were able to see two targets simultaneously while they were in the grey area.