THE NERVES AND MUSCLES OF THE PROBOS- 

 CIS OF THE BLOW FLY PHORMIA REGINA 

 MEIGEN IN RELATION TO FEEDING 

 RESPONSES ' 



By V. G. DETHIER 



Zoological Laboratory, University of Pennsylvania^ Philadelphia, Pa. 



INTRODUCTION 



To say that structure and function are inseparable is almost tauto- 

 logical ; nevertheless, in the early history of biology, and until very 

 recent times in entomology, structure has commonly been studied for 

 the sake of structure. Developmental morphologists and students of 

 phylogeny have approached the study of structure from a dynamic 

 point of view, but few entomological anatomists have come to the sub- 

 ject with the thought of function uppermost in their minds. Not infre- 

 quently it falls to the lot of the physiologist probing the functional 

 mysteries of some insect to survey and map his own anatomical route. 

 With the increased use of electrophysiological techniques by the physi- 

 ologist the need to know the pathways of various nerves, which trunks 

 contain afferent fibers and which efferent, the identity of muscle in- 

 nervation, the relations of various fibers to ganglia and to the en- 

 docrine system, and where to place electrodes has, with other needs 

 of a similar nature, become urgent. The study of finer structure has 

 thus taken on a new aspect engendered by recent advances in insect 

 physiology. The study of chemoreception in the blow fly Phormia 

 regina Meigen is a case in point. 



Since the first quarter of the century when Minnich (1922) demon- 

 strated that adult Lepidoptera respond to appropriate chemical stimu- 

 lation of the tarsi and mouth parts by extending the proboscis, the 

 proboscis response has been exploited by many investigators, notably, 

 Minnich himself (1922 to 1931), Frings (1946), Frings and O'Neal 

 (1946), Haslinger (1935), Dethier and Chadwick (1947), and 

 Dethier (1957) as a means of conducting quantitative physiological 

 and behavioral studies of the chemical senses. Grabowski and Dethier 

 (1954) and Dethier (1955) showed that it was possible to elicit a 

 complete behavioral response, that is, complete extension of the pro- 



^ Th!s work was aided by a grant from the National Science Foundation. 



157 



