SOME FACTORS CONTROLLING THE INGESTION OF CARBOHYDRATES BY THE BLOWFLY

¹ Department of Biology and Applied Physics Laboratory, The Johns Hopkins University, Baltimore 18, Md.

1. The ingestion of sucrose, glucose, fucose, sorbose, mannose, and lactose by the blowfly Phormia regina was studied by means of preference-aversion tests conducted for four-day periods; individual feeding tests; measurements of the sensitivity of the different chemoreceptor systems; measurements of volume intake of mixed solutions; and longevity tests.

2. The preference-aversion curves for all sugars studied indicated an increase in volume intake with increasing concentration up to an optimum point, after which there was a decrease in intake. At very low concentrations water was preferred to sugar.

3. Volume intake measured by individual feeding tests did not exhibit a pronounced decline at high concentrations. The difference between this finding and the one noted above resulted from the fact that flies ingested a maximum volume of concentrated solutions during the first visits to the pipette and then gradually ceased feeding altogether, while their ingestion of less concentrated solutions continued repeatedly over the entire test period. In all experiments the weight of sugar taken increased over the entire concentration range.

4. There is no relation between the amount of sugar taken and its nutritive value.

5. Volume intake is under sensory control. The coördinated actions of three principal chemosensory systems regulate the complete feeding reaction. The intake of mixed solutions depends upon the stimulating effectiveness of the mixture and whether or not any of the components exhibit synergism or inhibition. Some sugars show inhibition but no repellence.

6. The initiation of the feeding reaction is under sensory control. Continuance of feeding is dependent upon continuous sensory input. The rate of imbibition increases with concentration until viscosity begins to exert a restraining effect. The termination of feeding may be brought about by adaptation.

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