PHOTOPERIODIC CONTROL OF DIAPAUSE 609 



Table III. Temperature and the Photoperiodic Response: 

 Experiment 6, Results after 40 Days 



8.3°C 23.5°C 29.5°C 



October 19, 1955. Table III gives the photoperiods used and the 

 results after 40 days. The low-temperature portion of the experiment 

 was continued until 75 days had elapsed. The first pupations at this 

 low temperature occurred as follows: the 14-hr group on the 47th day, 

 13V^-hr group on the 61st day, and the 13-hr group on the 75th day. 



These temperature experiments showed that long photoperiods 

 were most effective in terminating diapause at intermediate tempera- 

 tures. Constant low temperature reduced the rate at which the larvae 

 responded, and constant high temperature prevented the response 

 completely, at least for 47 days. In both experiments mortality was 

 relatively high, particularly at the upper temperatures, perhaps indi- 

 cating that these temperatures were sufficiently high to have a general 

 adverse physiological effect. 



The possibility that failure to pupate at high temperatures resulted 

 from partial starvation due to increased metabolic rate was considered, 

 and for this reason a test was conducted to determine the effect of 

 starvation on the photoperiodic response. Two groups of 10 animals 

 each in dechlorinated tap water were placed on a 13Vi-hr photo- 

 period; one group was fed regularly and the other received no food. 

 Similar groups were maintained on photoperiods of llVi and 11 hr. 

 Of the survivors on the 13V^hr photoperiod 9 of 9 fed larvae and 6 of 

 10 starved larvae had pupated by the 40th day; in the same period 2 

 of 10 fed larvae and 1 of 9 starved larvae pupated on the 12Vi-hr 



