80 DWIGHT E. MINNICH 



The average response to M/10 quinine hydrochloride thus dif- 

 fered strikingly from that to IM saccharose. That this differ- 

 ence, together with the slight differences of distribution noted, 

 indicates a discrimination of the two stimuli, seems to me not 

 only possible, but very probable. A final statement, however, 

 cannot be made with certainty. 



From the evidence presented, it is quite clear that the tarsal 

 organs of Pyrameis are chemoreceptors of a rather wide range of 

 sensitivity. Through them the butterfly is able to differentiate 

 such solutions as IM saccharose and 2M NaCl from distilled 

 water and from one another. It is also able to differentiate M/10 

 quinine hydrochloride from distilled water, from 2M NaCl, and 

 probably from IM saccharose. The appropriate stimulation of 

 these organs leads to an extension of the proboscis, the initial act 

 in food taking. The tarsal organs are thus organs of chemical 

 sense, concerned in the discrimination of food substances, and 

 may be properly considered as organs of taste. 



GENERAL SUMMARY AND CONCLUSIONS 



1. In Pyrameis atalanta Linn, each of the four ambulatory 

 tarsi possesses contact chemoreceptors. 



2. The appropriate stimulation of these receptors produces a 

 response in the form of an extension of the proboscis. 



3. The manifestation of this response varies somewhat, depend- 

 ing upon the chemical nature of the stimulus and the nutritional 

 condition of the animal. 



4. An intensive study of these differences of response shows 

 that Pyrameis is able to distinguish the following substances 

 from one another through its tarsal organs: distilled water, IM 

 saccharose, and 2M NaCl. It is also able to distinguish M/10 

 quinine hj^dro chloride from distilled water, from 2M NaCl, and 

 probably from IM saccharose. 



5. The efficiency of distilled water in evoking the proboscis 

 response is directly dependent upon the nutritional condition of 

 the animal. 



