Why insects need blood vessels?

Insects do not have blood vessels. They have an open circulatory system, in which the blood (called hemolymph) flows freely throughout the body. This may seem like a primitive system, but it actually works very well for insects.

There are several advantages to having an open circulatory system. First, it is much simpler than a closed circulatory system, which requires blood vessels, valves, and a pump. This simplicity allows insects to be smaller and more agile than they would be if they had a closed circulatory system.

Second, an open circulatory system allows for a more rapid exchange of oxygen and carbon dioxide between the blood and the tissues. This is important for insects, which have a high metabolic rate and need to constantly exchange gases to stay alive.

Finally, an open circulatory system helps to distribute heat throughout the body, which is important for insects that live in cold climates.

In conclusion, insects do not need blood vessels because their open circulatory system is more efficient for their small size and high metabolic rate.