The structure and properties of an abdominal chordotonal organ in Carausius morosus and Blaberus discoidalis

Each side of the abdominal segments of the stick insect Carausius morosus contains a chordotonal organ lying longitudinally in a ventro-lateral position. These ventro-lateral chordotonal organs each possess two nerve cell bodies and two scolopales. There is a single attachment strand to the cuticle.Electrical recordings from the receptors show that they respond in a highly phasic manner to both stretching and subsequent relaxation of the attachment strand. They are sensitive to substrate vibration but are activated by ventilatory movements. The effects of ramp and square wave stimulation are examined. The rôle of the ventro-lateral chordotonal organs as ventilatory receptors is discussed and abdominal chordotonal organs of insects in general are reviewed.The ‘ventral phasic receptors’ of the cockroach are re-examined and shown to be chordotonal organs. They are re-named ‘mid-ventral’ chordotonal organs.