Rhythmic Activities and the Insect Nervous System

Abstract

The rhythmic activities of arthropods have received a lion’s share of the attention of neurophysiologists during the last two decades. For example, the swimmeret beat of crayfish and lobsters, walking in insects and crabs, ventilation in Limulus, crabs and insects, and insect flight, stridulation, grooming and swimming have all been the subjects of a number of studies: many more aspects remain to be explored as much insect behaviour is characterised by rhythmic swaying, rocking, twitching, wagging, waving and beating. In no case is the neural machinery completely understood, but properties of the motor output common to some examples suggest that similar types of neural interaction may underlie different rhythmical activities. Moreover some similarities to vertebrate locomotory patterns begin to appear. Curarized spinal dogfish for example are like some insects in that they may continue to produce locomotory patterns of motor impulses in the absence of phasic input (Roberts 1969). The stepping of cats is said to depend on the “cooperative activity of a relatively simple internal pattern-generating network” affected by proprioceptive input and set in motion by a system of descending neurones which act like the command neurones of Crustacea (Evarts 1971). Such suggested similarities encourage the further study of arthropod rhythmical systems and the search for common mechanisms among them.