THE BIoLoGy OF THE CHRYSOPIDAE 1323 
cocoon. It is possible that by the shifting abovt of the pupa in the 
cocoon, some area is weakened, so that when the pressure is exerted the 
rent begins. However, no observations have been made substantiating 
this theory. After the rent has been once started, the further pressure 
and emergence of the pupa causes it to broaden to almost a circle. 
Once out of the cocoon, the pupa must molt before it becomes an 
adult. This molt was the critical period in reared Chrysopidae; the 
fatality in these rearings was at first between thirty and sixty per cent. 
It was observed that as soon as the pupa had emerged, it walked around 
on the bottom of the vial and sought repeatedly to climb up the sides. 
When twigs or leaves were placed in the vial, the pupa climbed up at 
onee, holding on with its claws and occasionally using its jaws to assist 
it. After hastily investigating the leaf or twig, the pupa braced its legs 
and began the stretching and expanding process which makes possible 
the splitting of the pupal skin. The providing of materials enab:ing the 
pupae to climb and properly orient themselves greatly reduced fatali- 
ties. If suitable supports are not found, the pupae may not be able to 
molt, but may grow weaker and more inactive and finally die. A weak- 
ened pupa rarely succeeds in shedding the pupal skin, as the process is a 
strenuous one, requiring all the strength that the most active pupa can 
exert. Pupae may also be removed to plants, where the molt can take 
place under natural conditions. 
The pupal molt 
The shedding of the pupal skin corresponds very closely to a larval 
molt. The writer has frequently watched pupae shed their skins, 
under a lens, and one instance, that of a femaie of Chrysopa oculata, 
may be described as a typical case. 
The pupa emerged from the cocoon and was taken from the vial and 
placed on a plant. It walked around over the leaves excitedly, and thus 
investigated several leaves. Finally it took up its position near the end 
of astem. It braced its legs and began to inflate or expand itself by a 
series of regular movements simulating breathing. Numerous writers 
have commented on the phenomenon of so large an insect coming from 
such a small cocoon; in fact, the size of the expanded pupa is several 
times the size of the cocoon. The abdomen is extended to the normal 
adult length. The thorax also is expanded. There is considerable mus- 
cular movement during this expansion. The abdomen is raised and low- 
ered, and extended and contracted, alternately. The head is raised and 
lowered. This pupa continued the expansion for ten minutes. It rested 
for perhaps a minute, and then a series of movements, calculated to 
shift the abdomen forward, was begun. The abdomen and the thorax 
