Removing antennae and maxillae has little effect on feeding on normal host plants by two species of caterpillar

Models of feeding regulation postulate that chemosensory information from available food both initiates and maintains feeding. However, we find that removing antennae and maxillae (AM) from Manduca sexta and Diacrisia virginica larvae has little effect on amounts eaten, patterns of feeding, and the microstructure (each bite and pause) of feeding, as quickly as two days after the operation. However, there was a small change in the microstructure of feeding of AM D. virginica. Bite frequency of AM D. virginica was significantly lower than for controls when larvae began meals without exploring the food first. Exploring was also followed by longer chewing bouts. Acute effects of the ablation were tested using only Manduca. Six hours after the operation larvae ate less than most controls by eating fewer meals and by biting more slowly. Unilateral ablates also ate less 6h post-operatively, by eating fewer meals; their bite frequency was not low. These observations suggest that chemosensory input affects bite frequency but not other aspects of feeding. As quickly as 24h post-operatively other sensory input to the CNS of AM larvae may compensate for the reduction in chemosensory information, but overall, chemosensory input appears relatively unimportant in non-choice situations.