Behavioral neurobiology aims at explaining behavior at the level of neurons and neuronal circuits, based on linking comparative anatomy, and the observation and manipulation of nervous system activity with animal behavior. The numerical simplicity and the presence of identified neurons in insect nervous systems make them outstanding model systems for neurobiology. The insect nervous system has a common ground plan with functionally specialized regions for sensory processing, integration, and motor control. In holometabolous species, the nervous system is restructured during metamorphosis to support new behavior. Different forms of plasticity allow for behavioral adaptations in the adult stage. Neuronal circuits for behavior in Drosophila melanogaster can be effectively analysed with genetic tools, as exemplified for courtship and mating behavior. Recent developments in connectomics and genome editing are expected to further behavioral neurobiology in a broad range of species and permit a comprehensive comparative approach to the neurobiology of behavioral ecology.