When an insect breathes, through which spiracles does oxygen enter?

Insects breathe through a system of openings on their body called spiracles, which are connected to a network of tubes called tracheae. The spiracles can be located in various positions along the body, including anterior (front) and posterior (rear) regions.

In most insect species, specifically, the posterior spiracles are primarily responsible for the intake of oxygen. They allow oxygen from the environment to enter the tracheal system, facilitating gas exchange necessary for the insect's survival. While both anterior and posterior spiracles can play roles in respiration, it is the posterior spiracles that are most commonly recognized for the intake of oxygen.

Therefore, identifying the posterior spiracles as the correct point of oxygen entry aligns with biological studies of insect respiration, highlighting their functionality in the process. This understanding is vital for comprehending how insects manage oxygen supply, especially since they do not have lungs like vertebrates and rely heavily on this direct delivery system to meet their metabolic needs.