Insect Physiology Respiratory and circulatory systems
 Insect respiration happens without lungs. There is a system of internal tubes and sacs through which gases diffuse or are actively pumped. Air is taken in through openings on the sides of the abdomen called spiracles. As larvae, many insects have gills that can extract oxygen dissolved in water, while others need to rise to the water surface to replenish air supplies which may be held or trapped in special structures.