Question

how does respiration take place in insect

Answer 1

insects respire through their skin.

Answer 2

The tracheoles end within the body cells. Gases move by diffusion within the tracheal system. When the insect is less active the ends of the tracheoles contain fluid. It is where the fluid and gas meet (= the fluid/gas interface), that exchange of gases occurs (oxygen istaken up, carbon dioxide is given off).