Insect specific olfactory receptors are not an adaptation to a terrestrial insect lifestyle, but evolved later in insect evolution.

The insect odorant receptor gene family evolved at the base of the class Insecta before the evolution of flight and perhaps as an adaptation to terrestriality, and was therefore an important evolutionary novelty for insects.

Metabolic activity across all living things represents an organizing principle for the sense of smell in humans and animals.