SEASONAL HISTORY. 39 



fied to a more cylindrical form. To some extent the legs become 

 shorter and remain practically motionless. The white color changes 

 to a light pinkish tint, which is especially marked toward the extremi- 

 ties. Should the cell be destroyed during this period the larva is 

 incapable of making a new one, and in many instances, as has fre- 

 quently been observed in the breeding experiment, the larva fails to 



pupate. 



THE PUPA. 



THE PROCESS OF PUPATION. 



Pupation is the result of the changes brought about during the post- 

 larval stage. In the process of pupation the larval skin splits on the 

 back of the thorax and on the head, and the skin is ruptured along the 

 median line and in front along the V-shaped suture toward the mouth 

 (fig. 8, h). As the pupa frees itself from the larval skin it is of a 

 rather elongated form. The appendages are short, and the skin on 

 these parts is wrinkled in a circular manner. The light pink color is 

 particularly marked on portions around the spines, head, prothorax, 

 the points of the legs, and on the hind end of the body. The pupa is 

 at this stage very restless, turning the abdomen in a circular motion, 

 which, together with a contracting motion, brings about the expansion 

 of the appendages and the assuming of the normal shape of the pupae. 

 Unlike many pupse of beetles of this group, the larval skin is com- 

 pletely freed from the pupa. Within a short time the pupa becomes 

 whiter in color and the prominent spines turn darker as they harden. 



POSITION OF THE PUPA IN THE CELL. 



Within the cell the pupa is continually moving, often changing its 

 position and constantly turning the abdomen in a circular manner. 

 Normally the pupa lies on its back, and the soft body of the tender 

 creature is kept from close contact with the moist walls of the cell by 

 the spmes on the appendages and on the back of the body (fig. 9). 

 This function of the spines is undoubtedly of great importance in the 

 development of the pupa, since this is the critical period of the insect, 

 when the organs and in fact all the parts of the insect are recon- 

 structed in the formation of the adult or beetle. The pupa is com- 

 pletely helpless when removed from the cell and is incapable of 

 making a new one, and if left on the surface of the ground or covered 

 up with earth it almost invariably perishes. 



TIME OF PUPATION IN THE FIELD AND IN BREEDING CAGES. 



In the field during the summer of 1909 the first pupae were found 

 June 11, while in the breeding cages the first pupa was found June 15. 

 The time of pupation is indicated in Table XVII, showing the relative 

 occurrence of the pupae in the field. 



