Insect chemosensory behavior is often interpreted as though ecological decisions can be read directly from receptor identity, receptor abundance, or ligand sensitivity. That interpretation is increasingly difficult to sustain. Receptor repertoires differ in size, evolutionary history, co-expression, and functional specialization; peripheral neurons transform chemical input through receptor architecture, adaptation, and temporal coding; central circuits recode odor through inhibition, convergence, learning, and multisensory integration; and internal state changes how otherwise similar sensory information is translated into action. This article develops a proposed functional chemosensory architecture that treats ecological decision making as an emergent property of transformations across these levels rather than as the output of a single molecular detector. The framework distinguishes receptor repertoire composition from ligand tuning, peripheral coding from central representation, sensory representation from state-dependent valuation, and motor output from ecological signal value. It also preserves negative and limiting evidence, including weak correspondence between receptor repertoire size and eusociality, incomplete behavioral valence of individual olfactory receptor neurons, limited plasticity after naturalistic chronic odor exposure, and cases in which accessory proteins are not obligatory for robust odor responses. The framework is not presented as a universal mechanism. Instead, it organizes testable cross-level predictions while identifying taxonomic, developmental, environmental, methodological, and laboratory-to-field boundaries that must be resolved before receptor-level findings can support ecological inference.
