THE SWEET-POTATO LEAF-FOLDER. 7 



moths kept in confinement. The first lot were from larvae that issued 

 on June 21. Eight of these spent 13 days in the larva stages, and 

 2 pupated 14 days after issuing from the egg. The averages of the 

 daily maximum and minimum temperatures for this period, taken 

 from a self-registering thermograph, were 95.3° and 72.6° F., respec- 

 tively. 



The second lot of larvae were reared during August. They issued 

 on August 3. Two pupated 13 days after issuing from the egg, 

 while two required 14 days, one 15 days, and six 16 days for the 

 larva stages. For this period the average of the daily maximum 

 temperatures was 90° F. and the average of the daily minimum tem- 

 peratures 72.8° F. 



In the case of the larvae reared during August observations were 

 made to determine the length of time required for the various in- 

 stars. Because of the fact that after. the first five molts the larva 

 usually devours all of the cast skins, with the exception of the 

 tougher portion from the head, it is rather difficult to determine the 

 exact time of molting, especially in the early stages. The time spent 

 in each of the 6 instars was, however, ascertained from 7 larvae. 

 With two exceptions the periods were as follows : First instar, 3 days; 

 2d, 3d, 4th, and 5th instars, 2 days each; 6th instar, 5 days. One 

 larva spent 3 days in the second instar and another only 4 days in 

 the sixth instar. 



PREPARATION FOR PUPATION. 



After completing its growth the larva ceases feeding and con- 

 structs a cocoon, within which it transforms later to the pupa. Dur- 

 ing the period intervening between the time when the last food is 

 taken and the time of pupation the larva undergoes a gradual 

 change; it becomes shorter, the bluish-green color disappears, and 

 the larva becomes sluggish. 



In the insectary during July and August the time required in 

 preparation for pupation was, with few exceptions, two days. In a 

 few cases three days were required. Under the heading " Hiberna- 

 tion w the length of time passed in preparation for pupation by indi- 

 viduals that complete their larval growth later in the season is given. 



PUPATION. 



In the field and in the insectary pupae normally are found in 

 loose cocoons within the shelters made by the larvae. Larvae develop- 

 ing after the latter part of August sometimes construct in confine- 

 ment a somewhat different type of cocoon, which will be discussed 

 later. 



The pupa period occupied from 6 to 9 days in the insectary 

 during July and August. During September, 1915, two individuals 



