Chemosensory behavior is often described as though ligand detection is translated directly into attraction, avoidance, feeding, host seeking, or other actions. That shorthand obscures a sequence of biologically distinct transformations. Receptor identity and molecular architecture constrain which chemical signals can enter the nervous system; peripheral sensory neurons regulate sensitivity and can be reshaped by diet or systemic state; first-order circuits preserve some stimulus structure while transforming mixtures and channel combinations; higher-order networks integrate nonchemical cues, internal state, memory, and competing drives; and behavioral output remains subject to sensorimotor feedback. This article develops a proposed neurophysiological framework in which insect chemosensory decisions emerge from sequential but non-isolated processing stages rather than from a single receptor-to-behavior mapping. The framework separates receptor activation, transduction and gain control, primary neural representation, state-dependent integration, decision circuitry, and motor implementation while allowing feedback and cross-level modulation. Evidence from Drosophila, mosquitoes, honeybees, and locusts demonstrates both recurring organizational principles and important departures from canonical models. The framework therefore treats taxon, life stage, sex, stimulus context, and experimental setting as boundary conditions rather than nuisance variation. Its purpose is not to assert a universal insect circuit, but to provide a testable architecture for locating where chemical information is transformed, reweighted, integrated, or lost before action.
