174 THE PHYSIOLOGY OF INSECT SENSES 



been found to require up to thirty-five minutes for completion (Wolf 

 and Zerrahn-Wolf, 1935 a). In the intact eye of Calliphora, as measured 

 electrophysiologically, it has been found to require from minutes to 

 hours. In the isolated retina, however, adaptation is complete within 

 fractions of a second. It is proposed (Antrum, 1950, 1952, 1958) that 

 the positive potential from the centrifugal cells acts as a *bucking 

 potential' preventing sustained depolarization of the retinal cells. As 

 a corollary of this, resolution of faster rates of flicker becomes 

 possible. When the ganglia are removed the resulting monophasic 

 ERG is unable to follow flicker at the same high rates as the intact 

 eyes. 



Support for the idea that the positive component arises post- 

 synaptically has been obtained by poisoning with nicotine, a specific 



ABC 



Fig. 87. Position of the retina (R) in relation to the optic lobe (I, II, III) in 

 the developing dragonfly. A, young larva; B, older larva; C, imago. 

 (Redrawn from Autrum, 1958 after Viallanes, 1884.) 



synaptic poison. This treatment abohshes the positive components of 

 *fast' ERGs, leaving the negative portions unchanged, and has no 

 influence on *slow' ERGs, as in Dixippus (Autrum, 1958). 



Ruck (1958 a, 1958 b) has not been able to confirm the relation be- 

 tween wave form of the ERG, flicker, and adaptation in the eyes of 

 Apis mellifera, the dragonfly Pachydiplax longipennis, and Phormia 

 regina. He suggested that the lowering of flicker fusion frequency in 

 Antrum's experiments is due to injury and that actually the flicker 

 fusion characteristics of an eye are determined by the retinal elements 

 themselves. 



Other ideas on the subject of ERG components include Hassen- 

 stein's (1957) analysis of the ERG of Sarcophaga and Eristalis into a 

 diphasic component and a negative component and Naka's and 

 Kuwabara's (1959) conclusion that the ERG ofLucilia is composed of 

 a negative and a positive component, both of which originate in the 

 receptor layer. Burtt and Catton (1958), on the basis of an observed 



