606 



PHOTOPERIODISM IN INVERTEBRATES 



no pupations (noninductive), and a 13-hr photoperiod, which was 

 just as effective as the longer day lengths employed in terminating 

 diapause. In other experiments not reported here it was shown that 

 still longer photoperiods, including continuous light, were all essen- 

 tially of equal effectiveness. Midge larvae collected in North Carolina 

 were used in Experiments 2 and 3. Those for Experiment 2 were 

 collected on October 1, 1955, and the experiment ran 60 days begin- 

 ning October 12. Larvae for Experiment 3 were collected December 



12 13 



DAY LENGTH 



(HOURS LIGHT / 24 HOURS) 



Fig. 1. Day length and pupation: Maryland midges. (Experiment 1.) 



26, 1955; the experiment started January 12, 1956, and continued 

 40 days. The results of these two experiments (Table I) did not 

 demonstrate a clear difference between the response of North Carolina 

 and Maryland midges. Indeed, the results of Experiment 3 were more 

 similar to those of Experiment 1 than they were to Experiment 2. In 

 Experiment 2 fewer larvae had responded at long and intermediate 

 photoperiods than at corresponding day lengths after the same length 

 of time in Experiment 3. A possible explanation for this difference 

 will be considered in the discussion. 



