188 DWIGHT E. MINNICH 



causes a rather large proportion of these animals to respond. 

 Vanessa like Pyrameis, therefore, must possess contact chemo- 

 receptors in the tarsi. 



4' Conclusions 



1. In Pyrameis and Vanessa the reception of distance chemical 

 stimuli may effect an uncoiling of the proboscis. 



2. Many individuals failing to exhibit the proboscis response 

 under conditions affording only distance chemical stimuli may 

 be induced to do so by bringing the second tarsi in contact with 

 a substrate saturated with applejuice. There are, therefore, 

 located in the second tarsi, receptors which are stimulated by 

 contact with applejuice. 



3. These receptors are neither touch nor temperature organs, 

 for, as the number of responses indicates, they are differently 

 affected by distilled water and applejuice. They must, there- 

 fore, be chemoreceptors. 



4. In Pyrameis the antennae, labial palpi, and rudimentary 

 fore legs may be removed without essentially affecting the results 

 obtained from contact chemical stimulation of the tarsi. 



THE PRECISE LOCATION OF THE TARSAL CHEMORECEPTORS 



1. Experiments 



a. Relation of tarsi to substrate. In Pyrameis and Vanessa the 

 tarsi are five-jointed. The proximal segment is the longest, being 

 about one-half the length of the entire tarsus. It is followed by 

 four short distal segments the terminal of which carries four claws. 

 Normally, that portion of the leg which comes in contact with 

 the substrate consists entirely of tarsal segments. In order to 

 determine more precisely this relationship, a butterfly was 

 placed in the device, as shown in figure 4, and the positions of 

 the tarsal segments observed: first, on a hard substrate of rough 

 white paper, and, second, on a soft substrate of absorbent cotton 

 saturated with distilled water. 



As the animal struggled, the position of the legs frequently 

 changed. In practically all positions, however, the tibia and 



