CHEMICAL SENSITIVITY OF TARSI OF PYRAMEIS 69 



filter-paper, across the few intervening centimeters, and set do^^^l 

 with the feet in contact with a thin layer of cotton, contained in 

 a Syracuse watch-glass and saturated with the solution to be 

 tested. If the animal failed to respond promptly, various slight 

 manipulations were employed to make certain that the ventral 

 surface of every tarsus was afforded ample contact with the 

 stimulus. Thus, if there was no response during the first few 

 seconds of the trial, a slight, even pressure was given the holder, 

 thereby causing the distal portions of one or more tarsi to press 

 more firmly against the cotton and thus become immersed in the 

 solution. If still there was no evidence of response after twenty 

 to thirty seconds, the holder was turned slightly, forcing the 

 butterfly to shift the position of some of its legs. And if both 

 the above measures proved ineffective, toward the end of the trial 

 the animal was occasionally lifted gently and let down again. 



At the close of each trial the butterfly was placed over a watch- 

 glass containing distilled water, and the tarsi were thoroughly 

 rinsed. This was necessary in order to prevent contamination 

 of the stimulating substance in one trial by adhering material 

 from previous trials. If the proboscis remained, extended after 

 the trial, care was exercised to prevent the animals from drinking 

 at this time. After the legs had been well rinsed, the butterfly 

 was placed on clean filter-paper for a moment to absorb the 

 excess moisture, and was then returned to its cage. 



In the above manner, butterflies were tested with distilled 

 water and solutions of IM saccharose, 2M sodium chloride, and 

 M/10 quinine hydrochloride, four trials being made daily with 

 each of these substances. The order in which the four stimuli 

 were employed was varied from time to time and a minimum 

 rest period of fifteen minutes was allowed between consecutive 

 trials. 



The responses of each butterfly were studied under three nutri- 

 tional conditions: first, a condition in which the animal was 

 receiving neither food nor water; second, a condition in which 

 it was receiving water only, and, third, a condition in which it 

 was receiving both food and water. The general plan was the 

 following. Immediately upon hatching, the specimen was placed 



