LOCAL-CONTROL OF LEG MOVEMENTS AND MOTOR PATTERNS DURING GROOMING IN LOCUSTS

This study demonstrates that the thoracic and abdominal nervous system of locusts is sufficient to mediate several site-specific and distinc t grooming leg movements. Locusts can use a hindleg or middle leg to g room at least four ipsilateral thoracic and abdominal sites, without i nput from the brain, subesophageal ganglion, or prothoracic ganglion. The hindleg is used to groom the posterior abdomen, the ventral or pos terior hindleg coxa, and the ear; the middle leg is used to groom the anterior hindleg coxa. Grooming movements are often rhythmic and displ ay site-specific intralimb coordination patterns. During grooming of t he posterior abdomen or ventral hindleg coxa, for example, hindleg tib ial extension occurs nearly simultaneously with femur elevation, in co ntrast with locust hindleg movements during walking. Electromyographic (EMG) recordings during these movements show that rhythmic bursts of tibial extensor activity occur nearly in-phase with those of trochante ral levators, in contrast to hindleg EMGs during walking. During groom ing of the ear, hindleg tibial extension/flexion and tibial extensor/f lexor muscle bursts can occur independently of the femur elevation/dep ression and trochanteral levator/depressor muscle bursts, suggesting t hat the neural modules controlling tibial and femoral movements can be uncoupled during this behavior. Tibial extension can occur before, or even in the absence of, tibial extensor muscle activity, suggesting t hat spring-like properties of the leg and energy transfer from femur m otion may play important roles in such leg movements. Adjacent legs so metime show coordinated femur movement during grooming with one hindle g, suggesting that grooming may also involve interlimb coordination.