. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. UTILIZATION OF SUBSTANCES BY DROSOPHILA 110 stances should give much lower scores and be accordingly easier to single out. Guanine, for example, is clearly toxic. Variations in toxicity and in the flies themselves naturally militate against any sharp distinction, so that further experi- ments were performed to bring out hidden differences. The difference between toxic and repellent substances can sometimes be demonstrated readily by offering a questionable solution alone and in combination with a separate vial of water. Rham
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. UTILIZATION OF SUBSTANCES BY DROSOPHILA 110 stances should give much lower scores and be accordingly easier to single out. Guanine, for example, is clearly toxic. Variations in toxicity and in the flies themselves naturally militate against any sharp distinction, so that further experi- ments were performed to bring out hidden differences. The difference between toxic and repellent substances can sometimes be demonstrated readily by offering a questionable solution alone and in combination with a separate vial of water. Rhamnose alone, for example, gave a score of 68, but when the flies were offered. 10 15 20 DAYS OF SURVIVAL 30 FIGURE 1. The duration of life of adult fruit flies fed solutions of various sugars. Lactose, M/20, ; water, 3; xylose, M/10, X; galactose, M/10, O; glucose, M/10, o; sucrose, M/20, •; maltose, M/20, +; fructose, M/10, O. an additional vial of water, the score rose to 100. No discrimination was evidenced, and presumably the flies lived longer because they drank less of the rhamnose solu- tion. When repellency is suspected, however, something must be used to insure the ingestion of the solution. Vogel (1931) used sucrose solution, and a M/40 solution of sucrose was found useful in these experiments. Testing a large number of flies with this solution alone gave a score of 382. Table III shows how the results differed when various substances were added to it. Dulcitol alone is seem- ingly inert in M/10 solution, but when M/40 sucrose is added, the flies live longer than in sugar alone (score 508). Isoleucine is inert either way. D-Arabinose. on the other hand, prolongs life slightly when alone but shortens it when added to the sucrose solution, a puzzling result, to be sure. Sorbose would seem to be toxic either alone or in sucrose solutions, as do tartaric acid, norleucine and histidine, while valine, which is toxic when alone, can probably be detoxified when sucrose is pr
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
