ELECTROPHYSIOLOGICAL INVESTIGATION 



89 



Boeckh (1962) recently analysed some olfactory receptors of this animal in 

 detail. Among the numerous antennal sensilla of different types and un- 

 known function, he was able to find a uniform field of sensilla basiconica 

 which gave responses to olfactory stimuli. If an electrode is placed at the 



C. Bombyx 



B. 



Porthetria 



1 m 



'L 



Isec. 

 Fig. 3. A, Method of recording electroantennograms (EAG's) from moths. 

 Air is directed toward the antenna through a cartridge containing fiker paper 

 impregnated with an odorous solution of known concentration. B, EAG's from 

 Porthetria dispar. a and b, Responses to different concentrations of the natural 

 sex attractant. c, Response to the excised gland of a virgin female. C, EAG's 

 from Bombyx mori. a and b, Responses to different concentrations of the 

 synthetic sex attractant. c. Response to the excised gland of a virgin female 

 (from Block, Boeckh and Schneider, unpublished). 



base of one of these sensilla, apparently supplied by only one sensory nerve 

 fibre, receptor potential and nerve impulses are simultaneously recorded 

 during stimulation. Adequate stimuli are odour currents of decomposing 

 meat. But some chemically defined substances such as mercaptan, fatty 

 acids and amines elicited responses as well. Ammonia and H^S are without 

 effect upon the sensilla basiconica of Necrophorus thus far studied. 



The single Necrophorus receptor unit either reacts with a depolarization 

 of the receptor site and generation of impulses to stimuli such as rotting 

 meat, mercaptan, amines and homologous fatty acids with between 6 and 

 10 C-atoms, or with a hyperpolarization of the receptor site and inhibition 



