THE CATERPILLAR AND THE MOTH 



their purpose has been accomplished go into a state of dis- 

 solution during the pupal period. The debris of their 

 tissues is thrown into the blood, from which it is later ab- 

 sorbed as nutriment by the newly forming organs. The 

 caterpillar has a very elaborate system of muscles forming 

 a complicated network of fibers against the inner surface 

 of the body wall, some running longitudinally, others 

 transversely, and still others obliquely. Most of the 

 transverse and oblique fibers are not retained in the moth, 

 and if specimens of those muscles are examined during the 

 early part of the pupal period they are seen to have a weak 

 and abnormal appearance; the structure typical of healthy 

 muscle tissue is obscure or indistinctly evident in them, 

 and in places they are covered with groups of free oval 

 cells. These cells are probably phagocvtes. 



A phagocyte is a blood corpuscle that destroys foreign 

 proteid bodies in the blood, or any unhealthy tissue of the 

 body. It is not probable that the insect phagocytes are 

 the active cause of the destruction of the larval tissues, but 

 they do engulf and digest particles of the degenerating 

 tissues. They are present in large numbers in some insects 

 during metamorphosis, and are scarce or lacking in others. 

 The decadent state of the larval tissues that have passed 

 their period of activity lays them open to the attack of 

 the phagocytes, but these tissues will go into dissolution 

 by the solvent powers of the blood alone. Active, healthy 

 tissues are always immune from phagocytes. 



Some of the larval muscles may go over intact to the 

 adult stage, and others may require only a remodeling 

 or an addition of fibers to make them serviceable for the 

 purposes of the adult. The adult muscles that are com- 

 pletely suppressed during the larval stage appear to be 

 generated anew during the pupal stage. There is a dif- 

 ference of opinion among investigators as to how the new 

 muscles are developed, but it is probable that they take 

 their origin from the same tissues that built up the larval 

 muscles. 



