202 D WIGHT E. MINNICH 



such solutions as 1 M HCl, M/600 quinine sulphate, and 1 M 

 NaCl from either 1 M saccharose or distilled water. 



3. Distilled water alone is a very effective stimulus when 

 applied to the tarsi. 



4. The responsiveness to a 1 M NaCl solution may vary 

 widely from time to time. 



5. The ability of Pyrameis to distinguish the chemical nature 

 of substances in contact with its tarsi is independent of what- 

 ever sense organs may be present in the antennae, labial palpi, 

 and rudimentary fore legs. 



6. The tarsal organs are not osmotic organs. 



GENERAL SUMMARY AND CONCLUSIONS 



1. Pyrameis atalanta Linn, and Vanessa antiopa Linn, may 

 respond to the distance chemical stimuli afforded by applejuice 

 by uncoiling the proboscis. 



2. Many individuals failing to respond to these distance 

 stimuli alone, may be made to respond by bringing the second 

 tarsi in contact with the applejuice. If contact with distilled 

 water be substituted for contact with applejuice, the number 

 of responses is greatly reduced. Contact between the tarsi 

 and certain substances is, therefore, also able to effect the pro- 

 boscis response. 



3. The effectiveness of a given substance in stimulating the 

 tarsi is indicated by the percentage of responses which it pro- 

 duces. In this manner it can be shown that the sense organs 

 concerned are neither temperature organs, tactile organs, nor 

 osmotic organs, but chemical organs. 



4. The tarsal chemoreceptors are stimulated only through 

 intimate contact with the stimulating material, and hence are 

 contact chemoreceptors. 



5. The tarsal chemoreceptors are present, in the case of 

 Pyrameis — and the same probably holds for Vanessa also — in 

 all four tarsi of the walking legs. They are located in that 

 portion of the tarsi comprised by the distal end of the proximal 

 segment and the four distal segments. 



