Why do many terrestrial heteropterans have scent glands?

Many terrestrial heteropterans, particularly adult plant-sucking bugs, possess scent glands that serve as a primary mechanism for chemical defense. These glands typically open in front of the hind legs, allowing the insect to release unpleasant-smelling secretions when touched or threatened.1

This defensive strategy acts as a repellent against potential predators. The effectiveness of these odors is often enhanced by the insect's ability to produce poisons; the strong, unpleasant smell serves as a warning, playing a crucial role in the learning process of predators and thereby increasing the protective impact of the toxins. Due to these characteristic secretions, many members of this group are commonly referred to as stinkbugs.1