Male silkworm moths exhibit a simple odor searching behavior that involves fanning their wings while proceeding straight ahead and frequently turning in a zigzag pattern to locate the female. This behavior facilitates the detection of female sex pheromones with high sensitivity and selectivity using their antennae. Domesticated silkworm moths have lost the ability to fly; nevertheless, they continue to exhibit “wing fanning” behavior. Thus, it was hypothesized that wing fanning could be used to locate the source of an odor. However, the three-dimensional air movement caused by wing fanning, which guides the airflow toward the antennae, remains to be measured.

Associate Professor Terutsuki and his team artificially released pheromones using a small fan and used a high-speed camera to film male silkworm moths detecting the pheromones and fanning their wings. A silkworm moth movement model was reconstructed on a computer. Computational fluid dynamics (CFD) analysis performed subsequently revealed that wing fanning draws air currents into the antennae at a velocity of approximately 0.3 m/s. Furthermore, male silkworm moths selectively guided air currents to their antennae within a 60° forward range. These findings indicate that this airflow induction facilitates highly sensitive pheromone detection and efficient odor searching.

Associate Professor Terutsuki and his team developed an odor-detecting flying robot (bio-hybrid drone) (*3) that combines the antennae of an insect with a drone to locate the source of odors. These robots will facilitate the early detection of individuals in need of rescue at disaster relief sites. This study revealed that silkworm moths induce airflow by fanning their wings. These findings will enable the development of the abovementioned odor-detecting flying robot and robots that can rapidly detect the sources of odor in times of disasters.