454 



DWIGHT E. MINNICH 



In table 2 I have summarized the results obtained on all seven 

 butterflies. While the results there presented exhibit rather 

 wide individual difl"erences, they show the same general features 

 which are brought out in the behavior of butterfly no. 13. Thus 

 the threshold of response in all animals fluctuated directly with 

 the nutritional condition. Furthermore, the minimal effective 

 concentration after prolonged inanition with respect to saccharose 

 was very low in general. The extremely low thresholds, M/3200, 

 M/6400, and M/12,800, which were observed in four of the seven 

 animals, are particularly noteworthy. 



TABLE 2 



Shoiring the threshold concentrations of saccharose solution, under varying nutri- 

 tional conditions, in seven butterflies . An asterisk signifies the death of the 

 butterfly within twenty hours after the determination indicated 



This responsiveness to very dilute solutions of saccharose 

 affords further evidence of a point previously made by me, viz., 

 that the nature of tarsal stimulation is not osmotic, but chemical 

 (cf. Minnich '21, p. 198). Throughout the present experiments 

 all animals were tested four times daily with several solutions 

 other than those mentioned in this paper. Among these were 

 IM saccharose and 2M NaCl. On the days when the four butter- 

 flies mentioned in the foregoing paragraph were responding to 

 such dilutions of saccharose as M/3200, M/6400, and M/12,800, 

 three of the four gave no response whatever to 2M NaCl. Yet 

 the NaCl solution was vastly the more effective osmotically. 

 It might be objected that the salt solution produced such a 

 powerful osmotic effect as to inhibit response, whereas a more 



