448 DWIGHT E. MINNICH 



In selecting the concentrations of saccharose for making deter- 

 minations I followed no fixed, uniform procedure. Instead, 

 I was guided by the innnediate reaction of the individual together 

 with its previous behavior. In general, the first day of experi- 

 mentation was begun wdth a concentration of M/10 or M/lOO, 

 while each day thereafter was begun with the concentration 

 equal to or just below the threshold concentration of the previous 

 day. If this concentration produced a response, lesser concen- 

 trations were tried; if it produced no response, greater concentra- 

 tions were tried. This general procedure is brought out clearly 

 in column IV of table 1, where the concentrations used on but- 

 terfly no. 13 are given in the order tried, with the reaction 

 indicated in each case. 



The quality of saccharose employed in making solutions was 

 U. S. P. Stock solutions of M/10 and M/200 were made up 

 from time to time during the experiments, while the other dilu- 

 tions employed were prepared fresh daily from these stock 

 solutions. 



The present experiments were carried out at the same time 

 and on the same animals as the experiments described in a pre- 

 vious paper (Minnich, '21). For a more detailed account of 

 general methods than the one given here the reader is referred to 

 that paper. 



RESULTS 



A total of seven butterflies was experimented upon. Three 

 of these died quite early in the experiment, probably as a direct 

 result of starvation. Of the remaining four, two survived to 

 within a few days of the end of the experiment, while two others 

 not only survived the entire experiment, but were still in vigorous 

 condition several days later when they were killed and preserved 

 for further study. 



The most complete data were obtained on butterfly no. 13, 

 and, since they are typical of the results obtained on the ani- 

 mals as a whole, they are presented in full in table 1. It will be 

 noted that during the first three days after hatching no trials were 

 made. The first determination was thus made on the 4th day 

 when the threshold concentration was found to be M/200. 



