CHEMORECEPTION 155 



repugnant by the addition of hydrochloric acid, so that the category 

 bitter is not homogeneous for the bee. It is possible that investigations 

 of this kind would reveal similarly complex relationships in man. 



Other evidence as to the separation of the taste qualities in insects 

 was provided by Ritter ( 1 936), who found that after amputation of the 

 maxillary palpi specimens of Hydrous piceus would still react to 

 0'007M hydrochloric acid but not to salt, sugar, or quinine. Removal 

 of the tips of the labial palpi then abolished the response to acid, 

 although animals lacking both sets of palpi and the antennae still 

 reacted positively to meat juice, presumably via receptors in the mouth. 

 These observations would seem to set the acids apart from the other 

 taste substances, but are at variance with the findings of Bauer (1938) 

 with the same and related species, and of Hodgson (1951) with 

 Laccophihis. Bauer found that amputation of the maxillary palpi left 

 the gustatory response to sucrose, etc., unaltered except for an increase 

 in threshold. Hodgson found by ablation experiments that all the head 

 appendages could mediate responses to acids, salts, and alcohols. 

 Thresholds were increased considerably when the antennae were re- 

 moved, but less so when either pair of palpi were extirpated. 



