Hygro- and thermoreceptive triad in antennal sensillum of the stick insect,Carausius morosus

Summary The receptor cells in a poreless sensillum on the antenna ofCarausius morosus were examined electrophysiologically. Two of the units are antagonistic regarding humidity, one responding with an increase in impulse frequency to rising humidity (moistair unit) and the other to falling humidity (dry-air unit). Another reacts to falling temperature with a rise in impulse frequency (cold unit). In some cases responses from a fourth unit were also present. Its modality is uncertain. A method of marking the sensillum with a cactus needle for subsequent structural examination after recording is described.Supported by the Alexander von Humboldt Foundation and by the Fonds zur Förderung der wissenschaftlichen Forschung in ÖsterreichI wish to express my gratitude to Prof. Dr. F. Schaller and to Prof. Dr. H. Altner for their support of this study, to Dr. R. Loftus for very valuable discussion, and to Ms. C. Danner for her technical assistance.