bestir
themselves until they reach it; they move more at this stage than at any
other; and yet they would not move then if they were not hungry. Their
chief aim in life seems to be to eat. They are no travelers, that's
sure. Even when they emerge from the chrysalis into the moth they use
their wings very little, only fluttering a short distance when they are
mating."

"But suppose, Josef, that one wants to get them somewhere else and they
won't go," speculated Marie.

"Oh, it is easy enough to move them. That can be done any time by means
of a good tempting mulberry leaf; they will cling to it tight as a leach
and you can cart them round wherever you wish."

"When do you suppose our silkworms will first change their skins,
Josef?" asked Pierre.

"Moult?"

"Yes. I forgot the word for it."

"That all depends on the temperature of the room and on how fast they
develop. Usually with the degree of heat we keep here the first moulting
takes place within eight days. You see your silkworms are only about a
quarter of an inch long at first, and as they increase in size to about
three inches their skin is not elastic enough to accommodate their rapid
growth. It simply won't hold them. Suppose you or Marie grew twelve
times your natural size in a few short weeks?"

"I'd pity Mother, letting out our clothes!" chuckled Marie.

"They couldn't be let out; the material wouldn't be there," replied
Josef. "And it would be the same way with your skin. It wouldn't
stretch. You'd have to have a new one. That's what the silkworm
does--only it does it several times over. No skin made can cover an
animal that is a quarter of an inch long one week and three-quarters of
an inch long the next, and so on growing in leaps and bounds until it
gets up to three inches and sometimes more. Think of growing at that
rate! And the little gourmands are not eating all the time, either,
because after they are hatched it is three days before they eat much.
They act stupid, and as if they didn't feel well. But later they make up
for their loss of appetite--don't you fret."

Josef smiled grimly.

"By the fourth day they are eating at a furious rate," he went on, "and
they keep right on stuffing themselves for five days. When they are
about eight days old they have expanded until their skin is so tight
that it makes them uncomfortable. It seems to pinch and make them ill.
At any rate they act as if they felt pretty poorly and did not want to
eat mu