A vague notion that silk culture ought to form one of the industrial
pursuits of the American people seems to be prevalent enough; but it
does not take practical hold upon anybody. The nearest approach to
anything practical which we have seen, in late years--excepting, of
course, what has been done in California--occurred in New York in July
last, when a number of gentlemen pledged themselves, according to a
report given in the _Tribune_ of July 30, "to promote the native silk
trade."
The gentlemen present at the meeting represented the most prominent
silk manufacturing and importing houses in this country. What these
gentlemen have since done towards promoting the native silk trade, I
do not know, but, having pledged themselves, it is presumed they have
done something.
At the meeting, of which the _Tribune_ article is a report, dags,
and other things, manufactured from California silk, were exhibited;
and the report goes on to say that "Mr. Warren also exhibited samples
of native and foreign cocoons, and of raw and thrown silk, together
with the common _Cecropia_ and _Bombyx Cynthia_, species of
silkworms which feed upon oak leaves. * * Also the _Bombyx Yamamai_
which feeds upon mulberry leaves; also the _Bombyx Pernyi_, of
which the cocoons are early as good as the cocoons of worms fed upon
mulberry leaves."
I have given this extract, word for word, as it stands in the columns
of the _Tribune_, because it contains more blunders of one kind or
another than I remember ever to have seen in so many words. _Cecropia_
is certainly not very particular as to its food, but it is not an oak
feeder. _Cynthia_ will thrive on nothing except ailanthus, though it
will eat one or two other things, but not oak. The _Yamamai_, on
the other hand, will eat oak, indeed it is its natural food; but Mr.
Warren errs greatly when he says that it will feed on mulberry. The
last clause of the sentence, which says that cocoons of _Pernyi_ are
nearly as good as those of worms fed on mulberry leaves, must be a
sort of entomological joke, of which the point is not discoverable by
me, so I pass it over.
I do not, however, notice this report on account of its grammatical
and entomological mistakes. It is because of the evil effects it may,
and probably will, have on amateur silk culturists, that I notice
it; for most assuredly, failure will be the result of all attempts
to produce silk cocoons by feeding the caterpillars of the different
moths on the food prescribed by Mr. Warren. Any patriotic, money
making farmer, who believes in the _Tribune_, purchasing _Yamamai_
eggs and setting his worms to feed upon mulberry, which they refuse to
eat, and consequently, all die, will probably give up silk culture
as being nothing more or less than a humbug. And thus the cause is
injured.
For several years past, I have made some experiments in the rearing of
the silkworms, giving the result of my experience in the first year in
Vol. II., page 311, of the _American Naturalist_; and of a subsequent
year in the _Entomologist_, for November, 1869.
The paper in the _Naturalist_ is devoted to my experiments with the
ailanthus silkworm, _Samia Cynthia_ (G. & R.), a naturalized species
from the East. In that paper, I have said all that is necessary to
say at present, on that species, except perhaps that I am further
convinced, from the inspection of samples of sewing and other silks,
made from the cocoons of _Cynthia_, that one day it will be reared
very extensively in the United States. It is perfectly hardy, is
double brooded, and may be reared by any one possessed of a few acres
of land, which may be good enough for growing ailanthus trees, but
not good enough to grow any thing else. The labor of a few old men,
or women, or even children, is sufficient for the purpose. The cost is
therefore trifling.
The objection to the cultivation of _Cynthia_ is that the cocoon
cannot be reeled. But it can be carded, and if the Chinese can make
excellent silk goods from it, why cannot we? I suspect, too, that
_Cynthia_ silk can be worked in with cotton, or, perhaps, woolen
goods, adding to their beauty and durability (for it is indestructible
in wear), and thus open up branches of manufacture hitherto unknown.
For manufacturers of coarse goods, I have no doubt that the silk
from our native silk moths, _Cecropia_ and _Polyphemus_, may be used.
Indeed, I believe that M. Trouvelot is of opinion that _Polyphemus_
may fairly enter into competition with _Bombyx mori_, the ordinary
mulberry silkworm. The worm, however, is rather difficult to rear.
In reference, however, to _Bombyx mori_, it is well known that the
silk crop in France and Italy has been reduced greatly, and the price
of silk goods consequently enhanced, by prevalence of disease among
the worms. So much is this the case, that silk breeders have been
obliged to look around for some silk-producing moths whose products
may, at any rate, supplement the deficient crop. _Cynthia_, as already
mentioned as one of these, and two others mentioned by Warren in the
_Tribune_ reports above adverted to, are at present the subjects of
experiment.
My article mentioned before as appearing in the _American
Entomologist_ is mainly devoted to my experiments, and those of my
correspondents, with _Yamamai_, which, as I said before, is an oak
feeder. In Japan, which is its native country, it feeds, in its wild
state, on _Quercus serrata_. Whether that oak be found in America, I
do not know, but it is of little importance, as the worm will feed on
almost any species of oak, although I think that it prefers white oak.
The importance of acclimatizing new species of silk moths is of so
much prospective importance, that I shall devote the remainder of this
article to the consideration of whether _Yamamai_ and _Pernyi_ may not
be naturalized here. Any one, who happens to have the number of the
_Entomologist_ containing the article above alluded to, may find it
worth while to read it, but as many persons may not be able to obtain
that number, I will here repeat the substance of my remarks, adding as
much new matter as subsequent experience has afforded.
The silk from the _Yamamai_ being considered superior to that produced
by any other of the substitute silk moths, great efforts have been
made in Europe to acclimatize it; but, it must be confessed, hitherto
with but slight success. There are exceptions, however, particularly
among amateurs in Germany, sufficient to show that success is
possible. The Baron de Bretton raises about 27,000 cocoons annually.
In this country but little has been done, or attempted, and that
little has not been very successful.
The fact is, that _Yamamai_ is a difficult moth to rear in a country
like this, where in early spring the temperature varies so much; but
that success is possible, I am convinced.
The moth emerges from the cocoon in the latter part of the summer,
copulates, lays its eggs, and of course dies. And now the trouble
commences; that is, with eggs laid, say in Japan, from whence we
mainly get our supplies.
As soon as the egg is laid, the young larva commences its formation,
which in a short time (about one month) is perfected. It lies in the
egg in a quiescent state till early spring. If the egg remain in the
country where it is laid, and is kept at a pretty even temperature,
and free from damp, the caterpillar emerges in a healthy condition.
But if it be removed some thousands of miles, passing in the transit
from heat to cold, and back to heat again: and if, in addition, it
be closely confined in a damp place, with little or no circulation of
air, the egg is attacked by a fungus which sometimes prevents the worm
from emerging at all; or, if it emerge, it is in a sickly condition.
That these conditions obtain in the transit of eggs, from Japan
to Europe, and thence to America, is evident enough; and it may,
therefore, require the efforts of many persons, continued for a long
time, to enable us to acclimatize the _Yamamai_. But this is all that
is required, and I feel confident that ultimate success is certain.
On hatching out, the worm is of a brimstone yellow, and thinly covered
with strong hairs; after the second month it is greenish, with black,
longitudinal streaks, and the thread a dull coral red color. After the
third month it becomes of a fine apple green, with yellow tubercles
on each segment, from which issue a few black hairs. The head and legs
are chocolate brown, the prolegs reddish, and the first segment edged
with pinkish color. The greatest care is necessary, as the spring
advances, to prevent the eggs from hatching before the oak buds
are ready for them, and the temperature must be regulated with the
greatest nicety. If the eggs can be kept somewhere about 50 deg. Fah.,
it would be quite safe; higher than that the mercury should not be
allowed to rise, till you are quite ready for the worms, and, on the
other hand, the eggs should not be allowed to freeze.
On emerging from the eggs, the worms should be allowed either to crawl
to the oak branches, or rather to sprigs obtained for that purpose,
the end of which should be placed in a jar, or bottle, of water, or
the worms may be placed on gently with a camel-hair brush. The leaves
should be well sprinkled with clean water that the caterpillars may
drink.
From some cause, not well understood, the young caterpillars have
a tendency to wander; and if care be not taken many may be lost. To
prevent this, it is well to cover the branches with a gauze bag, tied
tightly around the stems, and close to the bottle. Care must also
be taken that the caterpillars do not find their way into the water,
which they assuredly will if they have the opportunity, committing
suicide in the most reckless manner. If the number of caterpillars be
few, it is a good plan to place them at the outset with their food,
in a wide-mouthed bottle, covering the mouth with gauze. The branches,
particularly if the weather be warm, must still be occasionally
sprinkled, so that the caterpillars may have the opportunity of
drinking. It must be remembered that experiment is necessary in
rearing _Yamamai_, but one thing is ascertained, and that is, that the
worms must not be exposed to direct sunshine, at least not after seven
or eight in the morning. If the spring be warm, I am inclined to think
that a northeastern exposure is the best, and we may sum up by saying,
that comparatively cool and moist seasons are more favorable to
success that hot, dry weather. In America the worms suffer in the
early spring, from the rapid changes of temperature, 40 deg. at 9 A.M.
increasing to 70 deg. in the afternoon and falling off to freezing point
during the night. The worms cannot stand this. They become torpid,
refuse to eat, and consequently die. To prevent this, if the nights
be cold, they must be placed where no such change of temperature can
occur.
It is scarcely necessary to say that an ample supply of fresh food
must be always supplied, but it may not be amiss to say that it is
well, when supplying fresh branches, to remove the worms from the old
to the new. The best way of doing this is to clip off the branch, or
leaf, on which the worm is resting, and tie, pin, or in some way affix
the same to the new branches. If this be not done, they will continue
to eat the old leaf, even if it be withered, and this induces disease.
If the worm has fastened itself for the purpose of moulting, the best
way is to remove the entire branch, clipping off all the dried
leaves before so removing it. These remarks apply, in general, to the
treatment of all silkworms, except _Bombyx mori_.
The results of numerous experiments with _Yamamai_ go to show that it
is, as I said before, a difficult worm to rear; but it has been reared
near New York to the extent of eight hundred cocoons out of sixteen
hundred eggs, and this, although not a remunerative result, is
encouraging.
The Chinese silk moth, _Aulterea Pernyi_, also an oak feeder, has been
successfully raised by me and by others, for several years. Eggs have
been sold to persons in States widely separated, and the results show
that this worm is perfectly hardy.
The moth winters in the cocoon, emerges early in May, if the weather
be warm, pairs readily, and lays from 150 to 200 eggs. These hatch
out in about fourteen days, and like _Yamamai_, always about 5 or 6
o'clock in the morning. It is necessary to be on the alert to catch
them on hatching only, and to remember that they are vagabonds, even
to a greater extent than _Yamamai_. Consequently similar precautions
must be taken.
The worm on emerging from the egg is large, and of a chocolate-brown
color. After the first month it becomes of a yellowish green; head,
pale brown; feet and prolegs of nearly the same color. The body has
numerous reddish tubercles, from which issue a few reddish hairs. At
the base of some of the tubercles on the anterior segments are silvery
patches.
The _Pernyi_ worm is much more easily reared than that of _Yamamai_,
but still great care is needed; fresh food of course is essential, and
a slight sprinkling of the branches and worms in very warm weather is
advisable; although it is not so necessary as with _Yamamai_. It is
remarkable that _Pernyi_ worms, fed in the open air, on oak trees,
do not, at present, thrive so well as those fed in-doors, but this,
doubtless, is a question of acclimation. I advise white oak (_Quercus
alba_) as food, if it can be readily obtained, but failing that, pin
oak (_Quercus palustris_) will do; and I have no doubt that they will
feed on any kind of oak. They will, indeed, feed on birch, and on
sweet gum (_Liquidambar_), but oak is the proper food. It is worthy of
remark that _Pernyi_ bears a strong resemblance to our _Polyphemus_,
but it is more easily reared in confinement, and double brooded; an
important fact for the silk culturist. From American reared eggs, I
obtained cocoons as early as July 4th, the perfect insect emerging on
July 31. Copulation immediately ensued, and the resulting eggs hatched
only on August 12, ten days only from the time of laying; and as the
worm feeds up in about four or five weeks, this affords plenty of
time for rearing the second brood. It must be remembered that on the
quantity and quality of food, much depends, not only with _Pernyi_
but with all caterpillars. By furnishing food sparingly the time of
feeding would be much prolonged.
I have already said that both _Yamamai_ and _Pernyi_ should be fed
under shelter for the reasons given, but there is another reason of
less importance. The young worms are liable to be attacked by spiders
and wasps, and even after the second month, they are not safe from
these enemies. I have seen a wasp bite a large caterpillar in two,
carry off the anterior section and return for the posterior, which
had held on by its prolegs. Did the wasp anticipate this fact, and
therefore carry off the anterior part first? As to the spiders, they
form a series of pulleys and hoist the caterpillar off its legs,
sucking its juices at leisure.
And now I must devote a few words to the advisability of silk culture
from a pecuniary point of view. _Bombyx mori_, or the ordinary
mulberry silkworm, is, of course, the best to rear, if you can obtain
healthy eggs. But this is the difficulty, and thence arises the
necessity of cultivating other silk-producing species. I imagine
that silk can be produced in most of the States of the Union, and
manufactured from the cocoon at a large profit; but for the present,
we will leave the manufacture out of the question, and consider only,
whether it will not pay to rear eggs and cocoons for sale? It must
be remembered that European manufacturers are at this moment largely
dependent on foreign countries for the supply of both eggs and
cocoons; and this, because of the general prevalence of disease among
all the races of _Bombyx mori_. And now, to what extent does the
reader suppose this dependence exists? Of cocoons I have no returns at
hand, but, of raw silk, European manufacturers purchase, annually, not
less than $160,000,000 worth; and of eggs (_Bombyx mori_) to the
value of $10,000,000. This, then, is a business of no trifling amount.
California seems to be alive to the fact, and, I am informed, raised,
this last season, $3,000,000 cocoons; and, for sale, about 4,000
ounces of eggs, worth at least $4 per ounce, wholesale. Now, there is
no earthly reason why California should monopolize this business.
Why are not companies formed in other States for this purpose? or if
private individuals lack the enterprise or the means, why do not the
legislatures, of those States most favorably located, do something by
way of starting the business? A few thousand dollars loaned, or even
donated, may prove to be a valuable investment for the people at
large, and, even supposing a failure, would not be a very great loss
to any body.
So far as farmers are concerned, it may interest them to know that one
man in England, Capt. Mason, clears $50 per acre by rearing silkworms
(_Bombyx mori_ in this case), and I much doubt whether any crop raised
here pays as well.
By way of commencement, then, let everybody that has sufficient
leisure set to work, and rear as many silkworms, of the above-named
species, as he possibly can; and if the process be not remunerative in
a pecuniary sense, it most assuredly will be in the amount of pleasure
and knowledge obtained.
One caution I must give to those who cultivate _Bombyx mori_. Although
_Yamamai_ requires sprinkled branches, _Bombyx mori_ does not; nor
must the leaves be furnished to them while wet with rain or dew.
* * * * *
EFFECT OF COLD UPON IRON.--The article upon this subject, giving
experiments of Fairbairn and others, referred to in our editorial
upon the same subject, in our last issue, was crowded out by press of
matter. The reader will find it in the present number.
* * * * *