Soil-adhesive or water repellent properties of the surface of cicada exuviae

Although the biology of cicadas is generally well known, knowledge about their exuviae is limited. The exuviae of the Kaempfer cicada is covered with soil, but the exuviae of the black giant cicada has almost no soil attached to it. We have focus on the surface structure of cicada exuviae, especially the soil adhesion and water repellency of the exuviae surface. The substance that adheres the soil to the exuviae surface of the Kaempfer cicada was extracted and isolated. We found that mucin contributes to the soil adhesion of the larvae surface of the Kaempfer cicada. The surface of the Kaempfer cicada shell has more hairs than that of the black giant cicada, also contributing to soil adhesion. We also show the abdominal part of the exuviae of both species exhibiting water repellency. The fact that water repellency located around the spiracles suggests that it is a feature that ensures breathing. Interestingly, the structure of this part was similar to that of the surface of a lotus leaf.