LIFE HISTORY OF THE MONARCH BUTTERFLY 37 
—the time depending on the temperature — into caterpillars 
that feed on the leaves of the milkweeds. Each caterpillar has 
three pairs of jointed legs near the 
head and five pairs of leg-like struc¬ 
tures along the posterior region 
that serve for clinging. The cater¬ 
pillar (larva) molts and each time 
grows larger but does not show 
any signs of wings like the grass¬ 
hopper. It is merely a larger 
caterpillar. 
Just before the fourth molt it 
attaches itself to a leaf or stem 
and hangs by a knot of silk with 
its head down for a few days until 
it molts for the fourth time. After 
this molt it is a pupa without legs 
or mouth parts. It is yellowish 
green in color, with golden spots. 
During this stage there is a strik¬ 
ing change taking place inside the 
green covering. Wings, new legs, 
different mouth parts with a long 
coiled tongue, and a nervous sys¬ 
tem of a different form are growing 
into working order while this pupa 
hangs so quietly. After a few 
days the green pupa case breaks 
open and the adult crawls out with 
the wings crumpled. Within a few 
hours the wings expand and push 
out the wrinkles and it is ready 
to fly away to feed on the nectar of flowers. This is an 
example of complete metamorphosis. (For explanation of 
metamorphosis see §§ 11, 12, 13.) 
Figure 21. — Larva of the 
Mourning Cloak Butterfly. 
It is gradually transform¬ 
ing into the pupal stage. 
In A notice the curve in 
the body of the larva and the 
attachment at the top. In 
B note that the exoskeleton 
first breaks on the back near 
the head. In C the exoskele¬ 
ton is being forced up toward 
the attachment at the top. 
In D the whole of the larval 
exoskeleton is removed and 
is shown shriveled at the 
right. In E the chrysalis is 
shortening and curving to the 
right. Compare E and A. 
Note that the short projec¬ 
tions on the left of E are not 
on the same side as the feet 
in A. Compare with Figure 
22. In F the chrysalis is still 
further shortened and curved. 
