170 THE PHYSIOLOGY OF INSECT SENSES 



and a small short negative d wave at the off. For Eristalis and Sarco- 

 phaga Hassenstein (1957) recorded an ERG with a very pronounced 

 positive on-effect followed by a slower negative wave and terminated 

 at the end of stimulation with a sharp negative off-efifect. These on- 

 and off-effects have the sign and position of the a and d waves res- 

 pectively. For Lucilia Kuwabara and Naka (1957) and Naka and 

 Kuwabara (1959) showed a simple positive monophasic wave at low 

 stimulus intensities. For Phormia regina the records of Ruck (1958 b) 

 showed at high intensities a small positive a wave and complex multi- 

 phasic waves with prominent negative components. The ERGs for 

 Apis mellifera and the dragonfly Pachydiplax longipennis were similar. 

 In his original papers Antrum (1948 a, 1948 b) described the ERG of 

 Calliphora as a diphasic response consisting of a spike-like positive 

 on-effect and a similar but negative off-effect (in these reports the po- 

 tential sign was incorrectly reversed but corrected in later papers). 

 With short flashes of light the wave was smoothly diphasic; with a 

 stimulus of long duration the positive wave returned to a line of zero 

 potential which continued until the off-effect. At high stimulus in- 

 tensities Antrum reported a *negatives Zwischenpotential*, and in a 

 later paper (Antrum and Hoffmann, 1960) figured the 'normal' ERG 

 as having a pronounced negative wave between the on- and off-effect. 

 The positive on-effect is sometimes preceded by a small negative wave 

 (Antrum, 1950; Kirschfeld, 1959). Similar ERGs have been described 

 for Apis, Bombus, Vespa, and the adult of Aeschna (Antrum and 

 Stoecker, 1950; Antrum and Gallwitz, 1951). 



Antrum decided that there are two fundamentally distinct kinds of 

 ERGs in insect eyes, the one, the Dixippus-typQ, purely negative and 

 monophasic, the other, the Calliphora-typQ, diphasic. In the first cate- 

 gory ('slow') he placed all of the slow-flying, night-flying, and aquatic 

 species (e.g., most Orthoptera, Blatteria, Lepidoptera, aquatic 

 Coleoptera, and dragonfly nymphs) ; in the second category ('fast'), 

 the rapidly flying species (Diptera and Hymenoptera). 



The wave forms of 'slow' and 'fast' eyes do not appear so radically 

 different in the records of most workers as they do in the records of 

 Antrum, Hassenstein, and Kirschfeld. Whereas the on- and off-effects 

 are the prominent features of the 'fast' eye as described and the slow 

 negative potential is negligible, the reverse is generally true in records 

 from other laboratories. Antrum has maintained that carefully 

 handled, fresh preparations are required to give reliable ERGs, and 

 both Hassenstein (1957) and Naka and Kuwabara (1959) have shown 

 that the ERGs of flies become monophasic as the preparation ages 



