HIBERNATION IN THE POTATO BEETLE. 



387 



nate. In control cages where nothing was fed, the beetles died 

 after u days. 



Beetles Fed on 



30 



25 



a 



ZO 



15 



10 



Foliage, tubers, 

 or fruit of 



Tomato 



Egg plant 



Foliage 1 

 Fruit = 



Potato 



Cucumber 



Potato foliaqe for 6 days 

 followed by sliced 



Polato 



Carrots 



Beets 



Squash 



FIG. 2. Represents the number of feeding days required on different foods 

 before the beetles entered a state of hibernation. Days are represented as ordi- 

 nates, different foods as abscissa. The solid line curve shows the average number 

 of days feeding on different foods before hibernation. The dotted line shows the 

 average number of days feeding on tuber or fruit before hibernation. 



In duplicate series of experiments conducted at the same time, 

 certain cages received water to replace usual evaporation from 

 the soil, others received no water. The addition of water to 

 cages containing normal food plants decreased the feeding period 

 from an average of 14.5 to 13.4 days. In control cages receiving 

 only water the beetles died after 16 days. In cages containing 

 non-solanaceous foods, the addition of water seemed to prolong 

 the life of the beetles without inducing hibernation. 



Breeding Activities. 



It is perhaps essential to emphasize that potato beetles of the 

 first generation used exclusively in these investigations indicated 



26 



