PKOCESS OF MOLTING. 



309 



molting. This area, which is but a narrow transverse line at 

 first, gradually widens and extends down each side of the 

 posterior margin of the head. It is widest on the dorsal line, 

 and is formed by the separation and projection forward of 

 the old chitinous covering of^ the head, while below and 

 beneath, the new light-colored head covering becomes visi- 

 ble. The light-colored area is apparently the top of the head 

 drawn back from the old covering, and protected by the 

 tightly stretched integument of the annulation. 



The caterpillar stops feeding usually from twenty-four to 

 forty-eight hours before molting, and rests quietly except for 

 occasional spasmodic twistings of the body. When the time 

 for molting arrives, the integument splits on the ventral part 

 of the annulation between the head and second segment and 

 partly up the sides. The caterpillar clings by means of its 

 prolegs to the surface on which it rests. It elevates the 

 middle segments, depresses segments four and five and ele- 

 vates the head and segments two and three. Its contortions, 

 at this stage, somewhat resemble the travelling movements 

 of a geometrid caterpillar, and, as the band over the light- 

 colored area behind the head is very tenacious, the caterpillar 

 bends itself nearly double ; the feet are then withdrawn by 

 a series of successive movements ; with a few more con- 

 tortions of the body sufficient force is developed to burst the 

 band in the rear of the head, and the dorsal surface of the 

 thoracic segments is molted. This stage requires about five 

 minutes from the first separation of the integument. The 

 head covering generally remains attached. 



By alternately contracting and expanding, the remaining 

 segments are molted one after another. The last three seg- 

 ments are generally molted in rapid succession, and the molt- 

 ing, with the exception of the head, is completed in about 

 fifteen minutes. After resting a few minutes the caterpillar 

 begins to rid itself of the firm head covering. This is done 

 by bending down the anterior segments, and then rubbing the 

 top, front and sides of the head upon the surface to which the 

 caterpillar clings. Finally, the top of the head covering is 

 loosened and pushed off. This process of molting the head 

 requires from fifteen minutes to half an hour, and the whole 

 process is completed in less than an hour. After molting 



