Bogner F, Boppré M, Ernst K-D, Boeckh J (1986) CO2 sensitive receptors on labial palps of Rhodogastria moths (Lepidoptera: Arctiidae): physiology, fine structure and central projection. J Comp Physiol 158: 741-749.
The tips of the labial palps of Rhodogastria possess a pit housing uniform sensilla, histologically characterized by wall-pores and receptor cells with lamellated outer dendrites. The receptor cell axons project to glomeruli in the deutocerebrum which are not innervated by antennal receptors. From their histology as well as from their central projection these sense organs are identical with palpal pit organs of other Lepidoptera. Physiologically, the palp-pit receptors respond uniformly; they are most excitable by stimulation with carbon dioxide while they exhibit relatively moderate responses to various odorants. The responses of CO2 show a steep dose-response characteristic. In ambient atmosphere (i.e., ca. 0.03% CO2) the cells are in an excited condition already; the seeming 'spontaneous activity' exhibited in air is decreased if the preparation is kept under N2 or O2 or CO2-free air. There is hardly any adaptation of the responses to continuous or repeated stimulation. Perhaps CO2 sensitivity is correlated with sensilla characterized by both wall-pores and lamellated dendrites. Pilot tests indicate that CO2 perception might be widespread in the Lepidoptera, but the biological significance remains obscure.
Rhodogastria = Amerila