Male cockroaches have colorless blood, while the female cockroaches may occasionally have orange blood. This is due to the absence of hemoglobin in their blood (the same cell that makes human blood red). Human beings use hemoglobin to carry oxygen, but cockroaches do not breathe the way we do. Cockroaches use a series of tubes called tracheae for breathing (and exhaling) and in fact they can breathe even in absence of a head. Cockroaches, like other insects, have an open circulatory system and their blood is also known as hemolymph (or haemolymph). It flows freely inside the body, touching all the internal organs and tissues. About 90% of this blood is watery fluid and the remaining 10% is made up of hemocytes. The oxygen is delivered by the tracheal system and not the circulatory system in a cockroaches (or most of the other insects).