THE PARASITES OE POPILLIA JAPONICA 13 
directly downward through the shell into the body of the host. The 
penetration of the heavy exoskeleton of Popillia japonica by so 
minute a larva is made possible by a modification in the structure of 
the tip of the mouth parts (fig. 11, D), which is provided with a row 
of heavy teeth forming a "rasper" by means of which a hole suffi- 
ciently large to permit of the passage of the body is made (fig. 12). 
The process of penetrating the 
thoracic wall is complete in 6 to 
12 hours after its commencement, 
provided the temperature is rea- 
sonably high. 
In the case of eggs deposited on 
other parts of the body, the larvae 
in many cases are unable to effect 
pTitranrp into tho hndv nronpr Fig. 12— Cross section oi egg of Centder cinerea 
eilUdllte IJItU lUt UOUy piopei. upon the heavily C hitinized thoracic wall of 
About hall Ol those deposited Popillia japonica, showing the aperture made 
n , -i , -i /> -l , r by the first-stage larva in entering the host 
ventraily on the thorax iail to pene- body 
trate on account of the extreme 
thickness of the exoskeleton at this point. When placed on the elytra 
few ever reach the body cavity, for having passed completely 
through the wing cover, they still lie free on the outer surface of 
the body. Under these conditions they are unable to drill the nec- 
essary hole in the derm and soon succumb. Eggs are occasionally 
placed upon the legs, and of these the ones placed upon the femora 
are capable of reaching the body cavity, but those on the tibiae 
very seldom do. 
The larval stages. — In considering the development of the larvae 
from the time of hatching onward, only those developing from eggs 
placed dorsally on the thorax will be dealt with, since this is the 
normal position. After penetration of the thoracic wall the young 
larvae move about somewhat in the thoracic cavity, and the first 
molt takes place in this portion of the body. Migration to the 
abdomen occurs almost immediately after the first molt. In the 
second stage the spiracles are each equipped with a strong hook 
(fig. 11, E), and dissections of living beetles containing these larvae 
indicate that the hooks serve to perforate and to attach the body 
temporarily to one or more of the numerous air sacs within the host, 
and that respiration is effected in this way. 
After leaving the thorax the larva gradually works its way back 
to the tip of the abdomen, after which it turns and once more enters 
the thorax. The death of the female host occurs just prior to this 
f)oint. The entire contents of the thorax are then consumed, the 
arva turns once more, enters the abdomen, and completes its feeding, 
usually devouring the entire body contents with the exception of 
some of the fully mature eggs. In the case of male beetles the second 
molt of the parasite takes place in the abdomen rather than in the 
thorax, and death of the host does not occur until the third stage is 
reached. Pupation takes place within the dead body of the beetle, 
with the head closely appressed to the tip of the abdomen. This 
occurs about four days after the death of the host. 
Molting of both of the early stages takes place by means of an 
anterior split in the derm rather than by its sloughing off in fragments, 
as occurs in many tachinid species. The process is very readily ob- 
served by placing living larvae of various stages in a normal saline 
solution, in which they will live for a considerable length of time. 
