vill] Introduction to Insects 87 
Most of us know the common large white butterfly 
which flies about gardens and fields during the summer. 
It is called the Large White Cabbage Butterfly, its 
scientific name being Pieris brassicae (see Fig. 27). 
If we watch this butterfly closely we shall see that it 
sometimes settles on a cabbage or a turnip or some 
allied plant and remains for a considerable time under- 
neath one of the leaves. If we wait at some distance 
until the butterfly flies away of its own accord and then 
examine the leaf on which the butterfly has been, a 
number of very small yellowish bodies arranged in a 
cluster may be found. They are almost skittle-shaped 
and marked by: longitudinal ridges (see Fig. 27a). 
In about ten days these disappear and are replaced 
by a number of small green worm-like creatures known 
as caterpillars. The small yellow bodies are the eggs 
of the butterfly, and were laid by the female. The 
small green caterpillars hatch from the eggs, eat the 
empty egg shells, and then begin to feed on the leaf, 
leaving marks where they have been feeding. They 
grow rapidly, but after a time growth ceases as 
the hard chitinous skin only allows of a certain 
expansion. At this stage the caterpillar fixes itself 
on a small silken web and a new skin is formed under 
the old one, the latter bursting and allowing the 
caterpillar to crawl out. It again grows rapidly and 
the new skin hardens. This process of casting the 
skin is repeated four or five times and allows the 
caterpillar to grow to a considerable size. When fully 
grown it measures about 2 inches or more in length. 
It is bluish green above and yellow below, having a 
long yellow line along its back, and also one along 
each side. These are broken by a number of black 
