English: The image, that is taken by scanning electron microscope, shows a detail of European Peacock's (Aglais io) feeler magnified at 7500x. This type of antennae, typical for butterflies, is called clavate (club-like), the segments of flagellum are gradually broaden towards apex. The butterflies’ feelers are primarily olfactory organs. In addition, they perform navigation, orientation and balance function. They are equipped with more than 16 000 olfactory sensors with different shapes (wrinkled scales, hairs or olfactory holes). The most common are olfactory scales (in the present case their density is approximately 150 000 per mm² and their width is from 6 to 11 μm). The olfactory sensors are very sensitive to the presence of pheromones and sugary substances and thus inform the butterfly about the presence of sexual partner or a potential food source. From those holes a bigger scales will grow out, that are structurally similar to the scales on the butterfly wings.