TARSAL CHEMORECEPTORS OF BUTTERFLIES 181 



adjusted so that it was on a level with the surrounding apple- 

 juice in the Petri dish. 



A butterfly was removed from the cage and placed in the 

 holder. When the death feint had worn off, it was tested in 

 one, two, or three different positions on the apparatus (fig. 

 1,1,2,3). 



In the first position, the animal was held as near the edge of 

 pan a as possible, the antennae reaching out over the cloth satu- 

 rated with applejuice, but the four walking legs on the screen. 

 (It will be recalled that among the Nymphalidae the anterior 

 pair of legs is rudimentary and subserves no locomotor function.) 

 In this position, therefore, the chemical stimuli received by the 

 animal consisted of distance stimuli only, viz., the vapors given 

 off by applejuice. 



In position 2 the animal was also subject to distance stimuli. 

 Qualitatively these were the same as in position 1, and quanti- 

 tatively they could not have differed greatly, since pan b, like 

 pan a, was everywhere surrounded by a relatively large area of 

 applejuice. But to these distance stimuli was added whatever 

 stimulation might be afforded by the contact of a portion of the 

 second tarsi (anterior ambulatory) with the cheese-cloth pack 

 saturated with distilled water. Naturally, the number of tarsal 

 segments in contact with the water-soaked substrate varied 

 somewhat from time to time, depending on the posture of the 

 entire leg. 



Position 3 bore the same relationship to pan a that position 

 2 did to pan h. The animal was thus subjected to the same 

 distance stimuli as in the two previous positions, but the second 

 tarsi were brought into contact with a cloth substrate saturated 

 with applejuice. 



The conditions of chemical stimulation in the three positions 

 above described may be summarized as follows : 



Position 1. Distance stimuli from applejuice. 



Position 2. Distance stimuli from applejuice plus contact 

 stimulus of distilled water on second tarsi. 



Position 3. Distance stimuli from applejuice plus contact 

 stimulus of applejuice on second tarsi. 



