SENSORY PHYSIOLOGICAL INVESTIGATION OF CARBON-DIOXIDE RECEPTORS IN LEPIDOPTERA

This report indicates that CO2-receptors are present in labial palp pits of various species of Lepidoptera, suggesting this to be a common occurrence and not to be restricted to certain taxonomic groups. Stimulation of the carbon dioxide receptors revealed uniform response to increasing CO2-concentrations and showed that receptors were responsive to the normal CO2-level in surrounding air (0.03%). Similar molecules such as CS2 did not elicit nearly as strong responses as carbon dioxide. The absolute levels of the dose-dependent responses in Lepidoptera showed great similarity to one another. Slight responses to stimulation by humidity or temperature were revealed to be actually dependent on trace CO2. Therefore these receptors may be designated as olfactory unimodal cells. So called "natural complex odour"-receptors in Pieris were rigorously retested and are shown here to be simple CO2-receptors. The biological function of these CO2-receptors remains a matter of speculation. For the vast majority of Lepidoptera, small differences in CO2-content of the immediate environment (the "microclimate") would be measurable. However, for the fraction of Lepidoptera occasionally exposed to high CO2-concentrations, the receptors could fulfill a more clear function.