Vol. LVI. 
No. 2481. 
NEW YORK. AUGUST 14. 1897 
*1.00 PER YEAR. 
LIFE HISTORY OF THE SILKWORM. 
HOW THE LITTLE INSECT LIVES AND SPINS 
Useful Work for the Schoolroom. 
Wbat are the history of the silkworm, its habits, and its method 
of getting the raw silk ? 11 . p. 
Dexter, N. Y. 
I wonder how many realize that the ordinary silk 
of commerce—that from which silk dresses, etc. are 
made—is supplied almost entirely by the caterpillars 
of an insect ! It is reported that, at last, man has 
succeeded in imitating this natural silk very closely 
by means of a machine which makes a certain kind of 
wood pulp into threads. Althotigh most people have 
worn silk in some form at some time, very few ever 
saw a silkworm or have any idea of its life-story. 
However, almost any one can raise silkworms, and no 
more instructive object lesson could be introduced 
into a schoolroom than a cage containing the insect 
at work. Let us see how the silkworm can be adapted 
to this educative use, and what might be seen by the 
pupils. 
The first requisite is to get the eggs of the insect 
for, like all caterpillars, 
silkworms hatch from 
eggs. Eggs may be ob¬ 
tained, not later than 
October (August and 
September) each year, 
ofE. Ilohagen, 840 Com¬ 
mon St., New Orleans, 
La. During the many 
centuries this insect has 
been cultivated, it has 
acquired many useful 
peculiarities and has, in 
fact, become a true do¬ 
mesticated animal. The 
white color of the in¬ 
sect, its seeming want 
of all desire to escape 
as long as it is kept 
supplied with food, and 
the loss of the power of 
flight (it has ample 
wings as Fig. 214 shows) 
on the part of the moth, 
are all, doubtless, the 
results of domestica¬ 
tion. It is said that, by 
breeding, as many vari¬ 
eties or races of the silk¬ 
worm have been pro¬ 
duced as there are of 
the domestic dog. For 
instance, the firm above mentioned quote prices on 
three varieties or strains of eggs ; those whose cater¬ 
pillars will spin pure yellow cocodns, those that spin 
yellow rose cocoons, and those which spin pure white 
Japanese cocoons. The eggs are sold by the ounce of 
30 grams. The price varies from $3 to $4, depending 
upon the variety. In each ounce, there are from 42,000 
to 55 000 eggs. Thus for a few cents, a gram (1,400 to 
1,800) of eggs may be purchased, and this will be 
amply sufficient for experimental or educational pur¬ 
poses. 
Over the top of an ordinary soap or starch box, 
tack some very fine meshed muslin, and arrange a 
glass door or a place to slide in a pane of glass in one 
side of the box. Put two or three inches of soil in 
the bottom of the box, sink several small vials for 
water in the soil, and your breeding cage is ready. 
The muslin will give plenty of air, and the glass will 
allow all operations of the insects to be watched. It 
will be practicable to breed the insects only during 
the spring and summer. Eggs ordered in August will 
not be ready to send until February or March of the 
following year, and must, of course, then be placed 
in a cold place to prevent hatching before spring 
opens and food can be obtained. The natural food 
of the caterpillar is mulberry, but this cannot be 
obtained in many parts of our country. Fortunately, 
the worms will thrive fairly well on the leaves of 
Osage orange, Ailanthus glandulosa, salsify, or even 
lettuce. It will require much labor to feed them on 
leaves of the last two plants, for the leaves wilt so 
soon. 
As soon as there is food in the spring, place the eggs 
in the cage and, when the caterpillars hatch out, 
have some fresh branches of whichever food is the 
most available in the bottles of water in the box. 
Very carefully transfer the minute young cater¬ 
pillars to the leaves. The eggs are nearly round, 
grayish-brown in color and resemble turnip seeds in 
size. The newly-hatched worm is dark gray and is 
covered with loDg, stiff hairs. It is imperative in 
raising silk-worms that the food be kept fresh ; this 
sometimes necessitates feeding several times a day. 
As the worms grow, their skins get too small and 
at intervals of a few days, they will be seen to attach 
themselves firmly to the branch and fast and rest for 
two or three days. At the end of this time, the old 
skins split open back of the head, and the caterpillars 
gradually crawl out of their old suits with new and 
elastic skins which allow them to grow some more. 
The worms will, usually, shed their skin or moult in 
this manner about four times before they get their 
full growth. It is usually estimated that a silkworm 
consumes its own weight of leaves every day it feeds. 
Yet, during the last few days of its life as a worm, it 
consumes more than during the whole of its previous 
worm existence. A full-grown silkworm measures 
about 2% times as large as the one near the bottle in 
Fig. 214. The worms are of a cream white color with 
a few darker markings, and have a slender horn pro¬ 
jecting from the back near the tail end. The insect 
spends from 25 to 40 days in the worm state, depend¬ 
ing upon the strain of the worm, its food, tempera¬ 
ture, etc. 
Having attained full growth, the caterpillar is ready 
to spin up. It shrinks somewhat in size, acquires a 
clear, pinkish hue, becomes restless, ceases to feed, 
and throws out silken threads. Some may be in¬ 
terested to know just how this silk is made that finally 
gets into silk dresses, etc. If a worm be carefully 
dissected, there will be found on each side of the 
food canal a long, narrow sac terminating in a con¬ 
voluted tube leading to a minute opening or spinneret 
on the under side of the lower lip. Some of the food 
which the caterpillar eats is elaborated in these tubes 
or sacs into a fluid. When the caterpillar spins a 
silken thread, some of this fluid is forced along each 
little tube on each side of the body, and these two 
streams finally unite in the spinneret and then appear 
through the opening as a single thread ; while in the 
caterpillar, the silk is in a fluid condition, but the 
moment it comes to the air through the spinneret, it 
at once hardens into a thread. 
The worms will spin up most anywhere in your box 
cage ; a few branches left in will afford them a good 
place. A silkworm usually consumes from three to 
five days in building its cocoon. Many of these cocoons 
are shown less than half natural s ! ze in Fig. 214. 
Three or four days after the cocoon is finished, if it 
be cut open, the caterpillar will be found to have cast 
off its skin and become 
quite a different look¬ 
ing object—a pupa. The 
cocoon is tough, strong, 
compact, and is com¬ 
posed of a firm, contin¬ 
uous thread, which is, 
however, not wound in 
concentric circles, as 
might be supposed, but 
irregularly, in short 
figure-of-8 loops, first 
in one place and then in 
another, so that, in reel¬ 
ing, several yards of 
silk may be taken off 
without the cocoon 
turning around. 
Normally, the insect 
remains in the pupa 
state within the cocoon 
for two or three weeks, 
when its skin bursts 
open and the adult in¬ 
sect, the white moth 
shown in Fig. 214 (less 
than one-half natural 
size) emerges. With no 
jaws, and confined with¬ 
in the narrow space of 
the cocoon, the motii 
finds some difficulty in 
escaping. For this purpose, it is provided, in two 
glands near the mouth, with a strongly alkaline 
liquid secretion, with which it moistens the end of the 
cocoon and dissolves the hard, gummy lining. Then, 
by a forward and backward motion, the prisoner, 
with crumpled and damp wings, gradually forces its 
way out; the exit once effected, the wings soon ex¬ 
pand and dry. The silken threads ^re simply pushed 
aside, but enough of them get broken in the process 
to render the cocoons from which the moths escape 
comparatively useless for reeling. Two such pierced 
cocoons are shown in Fig. 214. 
The broader antennae of the male moths enable one 
readily to distinguish them from the females. It is a 
curious fact that, although both sexes have ample 
wings, yet neither sex flies about. Each female may 
lay from 300 to 400 eggs ; usually each egg is covered 
with a gummy varnish which serves to stick the egg 
to the object upon which it is laid. Some varieties of 
the insect, however, do not thus stick their eggs 
down. The more profitable varieties of silkworms 
produce but one brood in a year; some hatch twice 
during the year, while others may have three, four, 
