TARSAL CHEMORECEPTORS OF BUTTERFLIES 179 



movement of the proboscis during one minute, a 'no response' 

 was recorded. With the 'no response' class, I have also in- 

 cluded a few questionable cases, in which I could not be certain 

 whether very faint movements had occurred or not. All such 

 cases have been indicated in the tables by interrogation marks. 



THE PRESENCE OF CHEMORECEPTORS IX THE TARSI 

 1. Apparatus 



The results of preliminarj^ observations and experiments soon 

 convinced me that there were present in the anterior walking 

 legs of Vanessa and Pyrameis, sense organs, the stimulation of 

 which evoked the proboscis response. ' To test this more fully, 

 the apparatus shown in figure 1 was constructed. It consisted 

 of a small wooden platform, uno' , bearing two wooden cross- 

 pieces, xx' and yy', which supported a tightly stretched wire 

 screen, s. The dimensions of this construction were such that 

 a glass Petri dish, p, 15 cm. in diameter and 1 cm. deep, could 

 just be slipped under the screen without contact with it. In 

 the Petri dish were mounted two small rectangular pans of tin, 

 a and 6. These were 4 cm. long, 2 cm. wide, and of such height 

 that their top edges were on a level with the rim of the Petri 

 dish. Two rectangular openings were cut in the screen, so that 

 when the Petri dish was in place they were directly over the pans. 

 Except these two places, the Petri dish was everywhere covered 

 by wire screen. 



Preliminary to each experiment, the apparatus was placed on 

 a tripod, on a table, and the Petri dish was filled with apple- 

 juice.- Two packs of cheese-cloth were folded to fit the pans. 

 One of these was saturated with applejuice and placed in pan a; 

 the other, saturated with distilled water, and placed in pan h. 

 In each case the exposed surface of the pack was carefully 



- Several of the bottled preparations of applejuice were used in the course 

 of these experiments. In the first part of the work on Vanessa I continued to 

 use from an opened bottle for several days, so that fermentation had set in toward 

 the end. In all subsequent experiments, however, a fresh bottle was opened each 

 day. 



