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86 The Animal Mind 



reactions to irritating chemicals, one would hardly be jus- 

 tified in saying that it possesses more than one food sensation 

 quality; while in our own case, of course, though we make 

 comparatively little use of the sense of smell, the qualitative 

 discriminations possible by its means are many. But we 

 come now to a group of animals where there appears a remark- 

 able development of qualitative variety in the sensations 

 resulting from chemical stimulation; namely, the Insecta. 

 As the reactions of animals to mechanical stimulation, on the 

 other hand, offer evidence of little qualitative difference in 

 the accompanying sensations, we shall give but slight atten- 

 tion to them in what follows. 



To begin with, there is evidence that taste and smell are 

 distinct in many insects. The water beetle Dytiscus margina- 

 lis, found apparently unresponsive to food at a distance, will 

 bite with especial eagerness at filter paper soaked in what 

 Nagel calls "a pleasant solution" (292). Ants fed honey 

 mixed with strychnine will taste it and then stop, and will do 

 this even when the antennae and mouth palpi are removed, 

 indicating that the taste organs are in the mouth itself (130). 

 Similar results have been obtained from similar tests on wasps, 

 and it has been observed that wasps so treated will hesitate 

 when offered pure honey afterward (439). 



Vitus Graber tested the reactions of various insects to odors 

 by the method which we called on page 60 the Method of Pref- 

 erence. This was Graber 's favorite mode of studying the 

 effect of stimuli upon animals. Applied to olfactory stimuli 

 it consisted in offering a choice between different compart- 

 ments, containing each a different odor. The animal's power 

 of discrimination was argued from the tendency to choose cer- 

 tain odors rather than others. Such preferences were shown 

 by the insects (152). The method, however, as was noted 

 above, is unsatisfactory, because discrimination might exist 



