4. MOTHS AND BUTTERFLIES. 
or black. An interesting collection may be made of these egos 
alone, and an entomologist can often tell from examining an egg the 
species of butterfly to which it belongs. 
When the larva emerges, so small and so unlike the mature 
insect, no one would guess what 1t was to be. It crawls to the tips of 
the tender young leaves and makes its first meal. It soon begins to 
grow rapidly ; and as it grows its skin becomes too small for its con- 
stantly increasing bulk, and a new skin begins to form under the old 
one, which after a short period of rest the caterpillar casts off. This 
is done-in the following manner: the insect first spins upon the 
leaf or twig upon which it rests a mat of silk to which it can hold 
firmly with its claws and claspers. It ceases to eat for a period and 
remains perfectly quiet upon the mat. It becomes so dull and sickly 
in appearance that one might suppose it was about to die. At 
length it begins to twist its head from side to side vigorously, and 
after a series of contortions in which the forward segmeuts swell and 
shrink alternately, the skin splits down the middle of the back and 
the rent is further enlarged by the struggles of the insect until it 
ean draw its head and legs out of the opening, when by securing a 
firm hold with its forward hooks it crawls out of its old skin look- 
ing as bright as a gold coin fresh from the mint. It is feeble and 
exhausted from its labors, while its skin and even its head and legs 
are soft and tender, and it now remains quiet until the skin dries and 
toughens by exposure, when it is ready once more to attack with 
renewed energy the tender leaves of its food plant. 
The cast-off skin sometimes retains the shape and colors of the 
caterpillar to a surprising degree —a veritable ghost of the former 
insect. Some caterpillars devour their outgrown garments as a first 
meal after each moult; others leave them where they were cast ; 
and one species carries in front of its head on a tuft of hairs, during 
its caterpillar life, the cast-off shells of its head which were shed 
with each change of skin, thus keeping in sight a record of its out- 
erownh coverings from infancy. When the caterpillars are gregarious 
these cast-off skins in groups representing each moult of the colony 
may frequently be seen on one plant. The moulting period is a crit- 
ical time in the life of the larva, for it is not only helpless to resist 
the attacks of enemies but it may die from exhaustion in the act of 
shedding its skin. 
The larva eats ravenously (sometimes devouring twice its weight 
of food in twenty-four hours) after it resumes activity, with a 
