This sesquiterpene hormone likely acted as a morphogenesis-to-differentiation switch in archaic embryos before it evolved its postembryonic function as the status quo regulator of insect metamorphosis.

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.

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

Developmental cell death plays a key role during insect neurogenesis and is increased in specific neuronal populations in flies that have evolved flightlessness.

Experiments exploring the role of juvenile hormone during the life cycle of firebrat insects provide clues about the evolution of metamorphosis.

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