Sensory Bristles and Sensory Scales Along the Wing Margin: Morphology, Modality, Arrangement, and Function

Many insect wings are not only motor organs that regulate airflow but also sensory organs that sense airflow and/or the movements of the wings themselves. In a large number of lepidopterans, two types of hair-like sensilla, called sensory bristles and sensory scales, are distributed along their wing margins. The morphology, arrangement, modality, and function of these sensilla are addressed in this chapter. The main contents are as follows. (i) Both the sensory bristle and scale of Pieris rapae (Pieridae), and the sensory bristle of Bombyx mori (Bombycidae) are sensitive to their own vibration. (ii) In P. rapae, both the sensory bristles and scales are complementarily distributed along most of the outer margins of both the dorsal and ventral surfaces of the coupled wings; the forewing and the hindwing of a lepidopteran in flight are partially coupled to each other. (iii) In Bombyx males whose bristles are immobilized, the wingbeat triggered by pheromone application soon stops, which implies that wingbeat sensing is responsible for wingbeat maintenance. (iv) Through the examination of bristle arrangement along the wing margins of 62 species of Papilionoidea, the bristle arrangement pattern is classified into eight types with different features. The contents (i)–(iv) suggest that the sensory information from the wing margin plays a significant role in the regulatory mechanism of wing movement and that the arrangement of the sensory bristles and scales along the wing margin is closely related to species-specific wing movement.