THE FINE STRUCTURE OF THE OLFACTORY 

 RECEPTORS OF THE BLOWFLY* 



V. G. Dethier, J. R. Larsen and J. R. Adams 

 Zoological Laboratories, University of Pennsylvania, Philadelphia 4, Pa. 



INTRODUCTION 



The principal site of olfactory receptors in the blowfly Phormia regina, 

 as in most insects, is the antennae. It has been demonstrated experi- 

 mentally that the blowfly is able to perceive a variety of odors, including 

 those of the normal aliphatic alcohols and aldehydes and a number of 

 natural products, through the medium of antennal receptors (Dethier, 

 Hackly, and Wagner-Jauregg, 1952 ; Dethier and Yost, 1952 ; Dethier, 

 1952, 1954, 1961). Furthermore, action potentials in response to stimula- 

 tion by 0.01 M aqueous solutions of NH4CI and NaCI have been recorded 

 from these receptors (Wolbarsht and Dethier, 1958). Nevertheless, the 

 identity of the olfactory receptors is in doubt and their exact structure 

 unknown even though a number of histological studies of the dipterous 

 antennae have been made (e.g. Liebermann, 1926). 



Establishing the identity of the olfactory receptors is made dilTicult by 

 the great numerical density of receptors, the variety of forms, and the 

 minute size of all. By studying all types of antennal receptors with the 

 electronmicroscope it has been possible to gain some idea as to the nature 

 of the olfactory receptors because the basic features of all are strikingly 

 similar. 



MATERIAL AND METHODS 



Antennae were removed from one-day-old flies in insect Ringers solution, 

 placed in a chilled solution of 1 per cent s-collidine-buflfered osmic acid 

 to which had been added 0.045 g/ml of sucrose, and stored at 2°-4°C for 

 2-4 hr. Dehydration was carried out in graded alcohols. The final 

 embedding mixture consisted of 90 parts butyl- and 10 parts methyl- 

 methacrylate. Two per cent Luperco CDB was employed to initiate 

 polymerization. Polymerization was completed in gelatin capsules placed 



* This work was aided by Grant B-1768 from the National Institute of Neurological 

 Disease and Blindness of the National Institutes of Health and by Grant G-6015 from 

 the National Science Foundation. 



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