Maxillary and labial sites of carbon dioxide-sensitive receptors of larvalOrthosoma brunneum (Forster) (Coleoptera, Cerambycidae)

Summary

Larvae of the wood-boring beetleOrthosoma brunneum respond positively to carbon dioxide (CO₂) by tending to move toward the highest concentrations of CO₂ while in a CO₂ gradient containing less than 10% CO₂ (Figs. 2,3). As is shown through experiments employing the amputation of various combinations of receptor organs, the CO₂-sensitive receptors of the larvae are situated on the distal segments of the maxillary palps and the labial palps but not on the antennae (Fig. 4). The maxillary palps are of primary importance in determining the response of the larvae to CO₂ gradients whereas their labial palps, though effective in mediating the response alone, play a secondary and weaker role. Since CO₂ receptors on insect labial palps have not been found before, the implications of this finding are discussed.