METHODS

We stuck flies to popsickle sticks by pushing their wings into a sticky wax werubbed on the sticks. Then we made a dilution series of glucose, maltose, and sucrose inone-half log molar steps (0.003M, 0.01M, 0.03M, 0.1M, 0.3M, and 1M) from the 1Mconcentrations of the sugars we were given. We tested the flies' sensory perception bygiving each fly the chance to feed from each sugar, starting with the lowest concentrationand working up. We rinsed the flies between tests by swishing their feet in distilled water.We counted a positive response whenever a fly lowered its proboscis. To ensure thatpositive responses were to sugars and not to water, we let them drink distilled water beforeeach test. See the lab handout Taste Reception in Flies (Biology Department, 2000) fordetails.RESULTSFlies responded to high concentrations (1M) of sugar by lowering their proboscesand feeding. The threshold concentration required to elicit a positive response from atleast 50% of the flies was lowest for sucrose, while the threshold concentration was highestfor glucose (Fig. 1). Hardly any flies responded to saccharin. Based on the results from all Fly?lab?report?p.?4 ????????????????????????????????Fly?lab?report?p.??the lab groups together, there was a major difference in the response of flies to the sugarsand to saccharin (Table 1). When all the sugars were considered together, this differencewas significant (t = 10.46, df = 8, p