194 D WIGHT E. MINNICH 



fore legs, with whatever chemoreceptors they may possess, in 

 nowise affects the response evoked by contact chemical stimu- 

 lation of the tarsi, is further confirmed. 



3. The tarsal chemoreceptors are stimulated through intimate 

 contact with the source of stimulating materials, and are, there- 

 fore, contact chemoreceptors. 



4. The receptors under consideration are, at least in the case 

 of Pyrameis, present in the tarsi of all four of the walking legs. 



SOME PRELIMINARY WORK ON THE NATURE OF THE TARSAL 

 CHEMORECEPTORS 



1. Experiments 



Having located the chemoreceptors of the four tarsi, I was 

 interested to discover, if possible, what substances the animal 

 was able to discriminate through these organs. There can be 

 no doubt that Pyrameis, as well as Vanessa, is able to distin- 

 guish certain substances from others in this way. The data 

 presented in tables 1, 2, and 3 show unmistakably that both 

 species distinguish applejuice from distilled water. The question, 

 therefore, to be answered was what classes of substances might 

 be distinguished. In man, there are four primary sensations of 

 taste, viz., sweet, sour, bitter, and salt. Pure water is to us 

 tasteless, although we readily detect its presence on the tongue 

 through touch and temperature organs. There is no reason to 

 suppose, a priori, that the same conditions necessarily hold for 

 Pyrameis. Substances which we taste may not be effective for 

 the tarsal organs of the butterfly, and vice versa. The data 

 presented in this connection are the results of preliminary experi- 

 ments only, but I have felt it advisable to present them here, 

 even though their final significance must be judged, at least in 

 part, in the light of further work. This work is now under 

 way. 



The method of experimentation was as follows. A Sja-acuse 

 watch-glass was filled with a thin, uniform pad of absorbent 

 cotton, cut to fit the glass, and the cotton was thoroughly satu- 

 rated with the solution to be tested. The butterfly to be tested 



