Preface 



Thirty years have elapsed since the appearance of Eltringham's 

 The Senses of Insects (first published 1933 in this series). In the inter- 

 vening time our knowledge of sensory physiology has advanced 

 further than during any previous period of study. The augmented 

 and accelerated advance may be attributed to new technological 

 developments and a notable increase in the number of research 

 workers interested in insects for their own sake or as material 

 uniquely suited to the solution of one or another basic biological 

 problem. 



The two most powerful modern tools placed at the disposal of the 

 sensory physiologist are electronic apparatus for detecting electrical 

 events in nerve tissue and the electron-microscope. The first has been 

 responsible for removing from the realm of mystery the function of 

 so-called Type II neurons in insects, for confirming the facts that 

 campaniform sensilla are mechano- rather than olfactory receptors, 

 and for initiating the unraveUing of the multitude of events that occur 

 as a part of vision. Electric recording from neural tissue has greatly 

 expanded our rather conservative estimation of sense organs in 

 general. 



Developments in the field of electronics has not, however, ren- 

 dered the behavioural approach to sensory physiology obsolete. 

 In fact, experiments in behaviour not infrequently point the direc- 

 tion that electrophysiological research should follow. Two cases in 

 point are the studies of the tympanic organ of moths and of the 

 chemoreceptors of flies. Without behavioural correlates the electro- 

 physiological findings are of small value. 



Just as behavioural studies have engendered electrophysiological 

 experiments, these in turn have driven the physiologist back to 

 structure. Whereas in many instances conventional histology has 

 been extended to its limit, in others it has barely scratched the sur- 

 face, and large areas of the nervous system are still empty areas 

 whose only detail is the notation 'unexplored'. Where light micro- 

 scopy has reached the limit of resolution, the electron-microscope 

 has opened up vast new areas of investigation and stimulated addi- 

 tional electrophysiological studies, which in turn have posed new 

 behavioural questions to bring the endeavour full turn. 



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