a, Fraction of synaptic output that is onto muscle for the neuron classes that make neuromuscular junctions. With the exception of IL1, classes for which greater than 30% of their chemical output is onto muscle are classified as motor neurons (mn). IL1 neurons—which are classified as sensory neurons (sn)—have clear sensory endings and sensory function; they are sensory–motor neurons, but we do not use that classification here. VC and HSN—hermaphrodite-specific neurons—innervate egg-laying muscles and have traditionally been considered motor neurons. The remaining neurons are classified as interneurons. Neurons that have previously been categorized as interneurons are indicated by a dagger. Neurons that have previously been categorized as motor neurons are indicated by an asterisk. b, Fraction of the input to the body-wall muscles of the head region and the remainder of the body that comes from neurons of various classes.