1. Regular shape: The cicada's cave is usually a regular shape, with a wide hole and a completely closed bottom. This shape is helpful for cicada's access and protection.

2. Strong material: the ground hole of cicada is formed by cicada larvae chewing the roots and soil of plants, and the material is relatively strong, which can provide sufficient support and protection.

3. Obvious exit: The cicada cave has obvious exit on the ground. These exits are small round holes, and the openings are flush with the ground for cicada larvae to climb out and complete metamorphosis.