Respiratory System

This chapter describes the respiratory system of insects. The primary goals of the insect respiratory system are to deliver oxygen from the air to the tissues and to transport carbon dioxide from the tissues to air. In contrast to many other animals, most oxygen and carbon dioxide transport occurs in the gas phase, with gases transported through the tracheal system by both diffusion and convection. However, insects do have oxygen-binding pigments that likely assist in gas exchange, with primitive insects having hemocyanin in the hemolymph and probably all insects possessing hemoglobin in certain tissues. The structures and physiological mechanisms of the respiratory system vary dramatically with phylogeny, developmental stage, and habitat. With a given tracheal structure, the ability of the tracheal system to transport gases can be modulated dramatically by varying spiracular opening, ventilation, and the fluid level in the tracheoles. In nut shell, the tracheal respiratory system of insects is a dynamic system, capable of a tremendous range of function and fine control. This light-weight, adaptable, high-capacity respiratory system is certainly one of the major traits which underlie the ecological and evolutionary success of insects.