An illustration of Spider and Insect describes their respiratory structures that shows airflow and book lung for spider and tracheal tubes and spiracles for insect. The following text are labeled on the illustration: Spiders respire using organs called book lungs, which are made of parallel, sheetlike layers of thin tissues that contain blood vessels. In most insects, a system of tracheal tubes extends throughout the body. Air enters and leaves the system through openings in the body surface called spiracles. In some insects, oxygen and carbon dioxide diffuse through the tracheal system, and in and out of body fluids. In other insects, body movements help pump air in and out of the tracheal system.