86 



DIETRICH SCHNEIDER 



such as salt (Dethier, 1955 ; Hodgson, Lettvin and Roeder, 1955 ; Wol- 

 barsht and Dethier, 1958). 



In connection with investigations of insect chemo-reception two ques- 

 tions have been repeatedly raised: 



1. Is it possible to distinguish between the " olfactory " and " gustatory " 



Fig. 1. Three-dimensional representation of a portion of a Bombyx antennal 



branch showing short, thin-walled sensilla basiconica and long, thick-walled 



sensilla trichodea (below) and one sensillum coeloconicum (above) (from 



Schneider and Kaissling, 1959). 



modalities, as in the case of mammals? — There are receptors which respond 

 specifically to water-soluble substances such as salt and sugar. Other 

 receptors are specifically responsive to air- or water-borne substances 

 which are water-insoluble or water- and lipoid-soluble, respectively. Both 

 receptors may be found side by side, not necessarily locahzed in restricted 



