The Bulletin 
89 
TRANSFORMATION OF PUPA 
The Molting of the Last Larval Skin 
Usually about forty-eight hours before a larva is ready to transform 
to a pupa it ceases to feed, assumes a straight, rigid form (Fig. 29), 
and commences to turn over and over inside of the cell. This seems 
to compact the material with which the cell is lined and at the same 
time smooths the interior of the cell. This stage may be known as the 
prepupal stage, and larvae usually assume this stage about forty-eight 
hours before they are ready to pupate. Cases have been observed, 
however, where the prepupal stage was assumed three days before 
pupation; in other cases, however, this stage is not assumed until the 
last day before pupation. 
Just before pupation actually takes place the perfectly formed pupa 
may be distinguished through the transparent larval chitin. The larval 
chitin splits first along the epicranial and frontal sutures, and the 
prothorax is the first part of the pupa to emerge clearly from the cast 
skin, due to the fact that the head of the pupa is, bent ventrally. Grad¬ 
ually the cast skin splits more and more posteriorly and is worked 
away from the body by the pupa turning and twisting its abdomen 
about (Fig. 31). The larval cast skin covering the legs and beak is the 
last to be freed from the pupa, this part of the cast skin frequently 
clinging to the pupa for several days. Usually the whole transforma¬ 
tion from prepupa to pupa takes place in thirty minutes, sometimes, 
however, it takes longer than this. In one case observed the splitting 
of the larval cast skin commenced at 6 in the evening but the pupa 
did not have its abdomen free from the larval cast skin until the next 
day between 9 and 10 in the morning. Such occurrences must be rare, 
however, for the only other case observed, where it required the pupa 
longer than an hour or two to free itself from the larval skin, the pupa 
died before it was able to free itself, indicating that it was not normal. 
The pupa is at first a pure translucent white, but in the course of a 
few hours it turns a pale straw yellow and retains this color until the 
developing adult’s dark colored body can be seen through the trans¬ 
lucent pupal skin (Figs. 48-50). This color can usually be noticed 
a day or two before the adult is ready to emerge. 
HABITS OF THE PUPA 
The pupa is naturally confined to its pupal cell. Therefore it has 
no habits that are especially interesting. When the pupa is disturbed 
it bends its abdomen first dorsally, then ventrally, and is thus able to 
rotate its body. It does not usually keep this process up very long 
before it relaxes. Usually the period of relaxation is approximately as 
long as the period of action which has just preceded. In most cases 
it takes a very violent disturbance to make the pupa become active 
before the period of relaxation has been of approximately the same 
