LIGHT REACTIONS — METABOLISM — MAY-FLY NYMPHS 447 

 EXPERIMENTS WITH POTASSIUM CYANIDE 



In the experiments with the negative Leptophlebia potassium 

 cyanide had proved an effective reagent in causing reversals. 

 With these Heptageninae at a concentration of N/500 it was 

 almost as effective in causing reversals as hydrochloric acid. 

 Of thirty tests run, 57 per cent were reversed by the cyanide 

 while the controls showed no reversals at all. Biometer tests 

 proved that the cyanide clearly depressed the nymphs. The 

 details are listed in table 11 and specimen results are shown in 

 chart 3. In all cases the nymphs were washed in water after 

 treating with KCN in order to keep the potassium from in- 

 terfering with the CO2 determination. 



In addition to the carbon dioxide tests, one nymph died while 

 moving positive, another just after reaching the positive end. 

 In all ten nymphs died in the experimental dishes as a result of 

 the cyanide treatment, of these six had reversed their reaction to 

 light shortly before dying. 



TABLE 11 



Showing the effect of N 1500 potassium cyanide upon nymphs negative to light and 

 upon their rate of carbon dioxide production 



