Final answer:
A transportation system to transport respiratory gases is not required in insects due to their highly efficient tracheal system, which delivers oxygen directly to cells through a network of tubes connected to external spiracles.
Step-by-step explanation:
Tracheal Systems and Insect Respiration
Insects do not require a transportation system like a circulatory system to transport respiratory gases because they possess a highly specialized tracheal system. The tracheal system is comprised of a network of tubes made of chitin that extends throughout the body, ensuring direct oxygen delivery to the cells. This system is extremely efficient due to its directness and allows for gas exchange without the need for oxygen to be carried by the blood.
The tracheal tubes are connected to the outside through spiracles located along the thorax and abdomen of the insect, which regulate the diffusion of CO₂ and water vapor. Moreover, some insects can actively ventilate their tracheal system with body movements, enhancing gas exchange.
An analogous system in some other animals is the "flow-through respiratory system," which includes features like multiple air sacs that further lighten the body mass and improve the efficiency of respiration. However, in insects, the tracheal system is unique and perfectly adapted for their respiratory needs, eliminating the requirement for a separate circulatory system for transporting gases.