Proprioception In Insects

1. A group of campaniform sensilla occurs on each of the joints of the maxillary palp of Periplaneta americana. Each group is supplied from a single large sensory nerve fibre. 2. Impulses in the nerves from the sensilla can be recorded at the base of the maxilla. Adaptation is slow and incomplete. 3. The sensilla respond to passive straight or sideways bending of the joint, and also strongly to pressure on the cuticle. They are excited only to a lesser extent when the segment is moved actively by its own muscle. 4. It is shown that the observations are consistent with the view that the campaniform sensilla are "stress receptors" responding to strains in the cuticular skeleton. 5. Their action as proprioceptors is compared with that of the vertebrate tension receptor.