Insects breathe using a network of tiny tubes called tracheae.

Explanation:
Insects have a unique respiratory system that allows them to breathe air. This system consists of a network of tiny tubes called tracheae. Here's a detailed explanation of how insects breathe using tracheae.

1. Structure of Tracheae:
- Tracheae are thin, branching tubes that extend throughout the body of an insect. They are made up of a tough, flexible material called chitin.
- These tubes connect to the outside environment through openings called spiracles, which are located on the sides of the insect's body.
- The spiracles can open and close to control the flow of air into and out of the tracheae.

2. Gas Exchange:
- The main function of the tracheae is to facilitate gas exchange. Oxygen from the air enters the tracheae through the spiracles and diffuses into the body tissues.
- Carbon dioxide, which is the waste product of respiration, diffuses out of the body tissues and into the tracheae.
- This exchange of gases occurs through a process called diffusion, where molecules move from areas of high concentration to areas of low concentration.

3. Branching System:
- The tracheae form a highly branched system that reaches all parts of the insect's body, ensuring that oxygen can be delivered to every cell.
- The larger tracheae branch into smaller tubes called tracheoles, which are even thinner and extend to individual cells.
- The tracheoles are lined with a thin, moist layer that helps facilitate the exchange of gases between the tracheae and the cells.

4. Adaptations:
- Insects have evolved several adaptations to enhance their respiratory system. For example, some insects have specialized structures, such as air sacs, that increase the volume of air they can hold.
- Additionally, insects can control the flow of air through their spiracles. They can open all spiracles to increase oxygen intake during high activity or close them partially or completely to conserve water.

In conclusion, insects breathe through a network of tiny tubes called tracheae. This unique respiratory system allows them to efficiently exchange gases with their environment, ensuring they receive the oxygen they need for survival.