380 W. D. FUNKHOUSER 



plete; in other species the old nymphal skin hangs to the end of the abdomen 

 of the adult and is carried about for some time after molting. 



Just before the last molt the skin dries out and becomes more or less 

 transparent and scaly. Under the microscope it is possible to distinguish 

 regions in which the integument has pulled away from the new skin even 

 before sphtting begins. 



The splitting occurs down the dorsal line but does not always start at 

 the same place. In most cases the first splitting occurs along the dorsal 

 line of the head; in a considerable number it begins near the thorax, and 

 in a few over the abdomen. 



The head generally emerges first, then the thorax, then the legs, and 

 lastly the abdomen. The various segments gradually enlarge as they are 

 freed, and become decidedly swollen within a few minutes following ecdysis. 

 In some species the thorax emerges before the head; in others the head, 

 the thorax, and the abdomen before the legs; and in a few the last pair 

 of legs and the last segments of the abdomen remain longest in the old 

 skin. These rather distinct types of ecdysis may be illustrated by the 

 common species Vanduzea arquata, Thelia himaculata, and Ceresa horealis. 



In Vanduzea arquata the nymph attaches itself securely by the first 

 pair of legs to the underside of a leaf. The splitting begins over the 

 thorax and the dorsal part of the thorax emerges first; this is followed 

 by the head, then the legs, and then the abdomen. The old skin is very 

 perfect and remains attached to the leaf. 



In Thelia himaculata the insect is not attached. The splitting begins 

 over the head and this part of the body emerges first; then the thorax 

 appears and the mtegument breaks around the coxae and the femora, 

 leaving pieces of old skin attached to the legs for some time after ecdj^sis 

 is completed; the abdomen is then removed, and lastly the legs. The old 

 skin is very imperfect, being much broken and torn, and drops to the 

 ground after the process is completed. 



In Ceresa horealis the insect is not attached. The splitting begins 

 over the head and gradually continues over the thorax and the abdomen. 

 The head emerges first, then the thorax, then the first half of the abdomen, 

 then the legs, and then the posterior half of the abdomen. The old 

 skin is very perfect and remains attached to the tip of the abdomen, 

 where it is dragged behind for some time. 



