66 D WIGHT E. MINNICH 



there was but one failure to respond. On completion of the 

 trial with the sugar solution, the tarsus which had been tested was 

 carefully rinsed by immersing in distilled water, and the butterfly 

 was returned to its cage. Fifteen minutes later another tarsus 

 was tested in the same manner, and so on, until each of the 

 ambulatory tarsi had again been tested twice. 



The data obtained from the above experiment are presented in 

 table 1 . It will be noted that specimens, both before and after 

 access to water, exhibited essentially the same behavior toward the 

 tactile stimuli afforded by the metal of the wire screen and the 

 cotton of the dry swab, viz., failed to respond. It is true that in 

 the case of the starved animals there were three trials in which 

 partial extensions of the proboscis were produced by contact with 

 dry cotton. Possible explanations of these responses will be 

 discussed later. In comparison with the other stimuli employed, 

 however, the response to dry cotton was virtually zero. With 

 the cotton soaked in distilled water, the situation was very dif- 

 ferent. Before the animal was allowed access to water, this form 

 of stimulus was 87.5 per cent efficient in producing a response, 

 whereas after access to water, it was but 4.2 per cent efficient. 

 Yet after this virtual disappearance of the response to water, a 

 IM saccharose solution was still 91.7 per cent efficient in evoking 

 a response. 



As noted above, a dry cotton swab applied to the tarsus occa- 

 sionally elicited a slight response. Precisely what was the effec- 

 tive stimulus afforded by the cotton? Two possibilities may be 

 suggested: first, the mere contact (pressure) of the cotton; 

 second, the hygroscopic water present on the cotton fibers. The 

 fact that the few slight responses observed were in starved animals 

 and that these responses disappeared after access to water lends 

 support to the latter suggestion. A final statement, however, 

 as to the effective stimulus in these responses is not possible, at 

 least not from the present data. 



Returning to a consideration of table 1, the following facts are 

 brought out clearly by the data there presented. First, contact 

 (pressure) stimuli alone, such as those afforded by wire screen or 

 dry cotton, when applied to the tarsi have little or no effect in 



