Respiration in the Desert Locust

1. Normal (dorso-ventral) and three auxiliary ventilating mechanisms (neck, prothoracic and abdominal longitudinal) are described in the non-flying Schistocerca gregaria. 2. Neck and prothoracic ventilation together contribute 14% of the maximum volume of air pumped by the insect. Head ganglion receptors must be stimulated for these forms to appear. 3. The metathoracic ganglion may contain a pacemaker controlling the frequency and amplitude of all forms of ventilation. Each head and thoracic ganglion contains carbon-dioxide receptors which modify the activity of the pacemaker. There is no control from the abdomen in the intact insect, or from receptors outside the central nervous system. 4. Oscilloscope recordings from the isolated central nervous system demonstrate a rhythm, which is modified and possibly initiated by carbon dioxide. 5. It is suggested that carbon dioxide normally provides a more important ventilatory stimulus than oxygen lack.