CHEMICAL SENSITIVITY OF TARSI OF PYRAMEIS 63 



its natural environment. The importance of water in this con- 

 nection is too obvious to require comment. As for saccharose, 

 it is one of the chief organic compounds present in the substances 

 on which this species feeds, viz., fruit juices, exuding sap, and 

 nectar. Thus apple juice is very attractive to these animals, 

 and, if available, may constitute one of their chief foods in the 

 autumn. In orchards where fallen apples litter the ground, 1 

 have observed great numbers of the butterflies feeding, just 

 prior to hibernation. According to Browne ('99, pp. 9 and 10) 

 the flesh of the average ripe apple contains 4 per cent of sac- 

 charose, this being, with the exception of water (84 per cent) and 

 invert sugar (8 per cent), the only substance constituting more 

 than 1 per cent of the total composition. Sodium chloride was 

 selected as a common inorganic salt encountered by butterflies 

 in surface waters. It is well known that many species of lepi- 

 doptera congregate about drying pools of water, and pools which 

 have been contaminated with urine or manure seem particularly 

 attractive. In such situations, NaCl is present in considerable 

 quantity. 



Saccharose and sodium chloride, in addition to the fact that 

 they are frequently encountered by Pyrameis in its natural habi- 

 tat, happen also to be substances which afford adequate stimuli 

 for two of the four primary taste sensations in man, viz., sweet 

 and salt. Quinine hydrochloride was chosenfor experimentation, 

 because it affords the adequate stimulus for a third of the human 

 taste sensations, viz., bitter. With Putter ('11, p. 608) I agree 

 that there is not the slightest reason to suppose that a substance 

 which affects the human taste organs in a certain way will affect 

 the taste organs of a lower animal in the same way. It was not 

 to ascertain whether Pyrameis could distinguish bitter that 

 quinine hydrochloride was chosen, but rather to discover whether 

 this salt, which produces such a bitter and disagreeable sensation 

 when applied to the human tongue, would produce or fail to pro- 

 duce a reaction in the butterfly. 



