Scientific American Supplement, No. 344, August 5, 1882

V >> Various >> Scientific American Supplement, No. 344, August 5, 1882

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On the trees were to be seen--_Attacus cynthia_ (the Ailantus silkworm),
the rearing of which was, as usual, most successful; _Samia cecropia_
and _Samia gloveri_, from America; also hybrids of _Gloveri cecropia_
and _Cecropia gloveri_; _Samia promethea_ and _Telea polyphemus_;
_Attacus pernyi_, and a new hybrid, which I obtained this last season by
the crossing of Pernyi with Royle. For the first time I reared _Actias
selene_, from India, on a nut-tree in the garden, and _Attacus atlas_,
on the ailantus. The _Selene_ larvae reached their fifth and last stage.
The Atlas larvae only reached the third stage, and were destroyed by the
heavy rains; only two remained on the tree till about the 8th or 9th of
September, when they had to be removed. I shall now reproduce the notes
I took on some of the various species I reared.

_Actias Selene_.--With sixty cocoons I only obtained one pairing. The
moths emerged from the beginning of March till the 13th of August,
at intervals of some duration, or in batches of males or females. I
obtained a pairing of Selene on the 30toh of June, 1881, and the worms
commenced to hatch on the 13th of July. The larvae in first stage are of
a fine brown-red, with a broad black band in the middle of the body. The
second stage commenced on the 20th of July; larvae, of a lighter reddish
color, without the black band; tubercles black. Third stage commenced on
the 28th of July; larvae green; the first four tubercles yellow, with a
black ring at the base; other tubercles, orange yellow. Fourth stage
commenced on the 6th of August; larvae green; first four tubercles
golden-yellow, the others orange-red. Fifth stage commenced on the 19th
of August; first four tubercles yellow, with a black ring at the base;
other tubercles yellow, slightly tinged with orange-red; lateral band
brown and greenish yellow; head and forelegs dark-brown. As stated
before, the larvae were reared on a nut-tree in the garden, till the last
stage. Selene feeds on various trees--walnut, wild cherry, wild pear,
etc. In Ceylon (at Kandy), it is found on the wild olive tree. As far as
I am informed by correspondents in Ceylon, this species is not found--or
is seldom found--on the coasts, but _Attacus atlas_ and Mylitta are
commonly found there.

_Attacus (antheroea) roylei_ (with sixty cocoons); three pairings only
were obtained, and this species I found the most difficult to pair in
captivity. Two moths emerged on the 5th of March, a male and a female,
and a pairing was obtained; but the weather being then too cold, the ova
were not fertile, the female moth, after laying about two hundred eggs,
lived till the 22d of March, which is a very long time; this was owing
to the low temperature. The moths emerged afterward from the 8th of
April till the 25th of June. A pairing took place on the 2d of June, and
another on the 6th of June.

Roylei (the Himalaya oak silkworm) is very closely allied to Pernyi, the
Chinese oak silkworm; the Roylei moths are of a lighter color, but the
larvae of both species can hardly be distinguished from one another.
The principal difference between the two species is in the cocoon. The
Roylei cocoon is within a very large and tough envelope, while that of
Pernyi has no outer envelope at all. The larvae of Roylei I reared did
not thrive, and the small number I had only went to the fourth stage,
owing to several causes. I bred them under glass, in a green-house. A
certain number of the larvae were unable to cut the shell of the egg.

Here are a few notes I find in my book: Ova of Roylei commenced to hatch
on the 29th of June; second stage commenced on the 9th of July. The
larvae in the first two stages seemed to me similar to those of Pernyi,
as far as I could see. In second stage, the tubercles were of a
brilliant orange-red; on anal segment, blue dot on each side. Third
stage, four rows of orange-yellow tubercles, two blue dots on anal
segment, brilliant gold metallic spots at the base of the tubercles on
the back, and silver metallic spots at the base of the tubercles on the
sides. No further notes taken.

One of my correspondents in Vienna (Austria) obtained a remarkable
success in the rearing of Roylei. From the twenty-five eggs he had
twenty-three larvae hatched, which produced twenty-three fine cocoons.
The same correspondent, with thirty-five eggs of _Samia gloveri_,
obtained twenty cocoons. My other correspondents did not obtain any
success in rearing these two species, as far as I know.

_Hybrid Roylei-Pernyi_.--I have said that it is extremely difficult to
obtain the pairing of Roylei moths in captivity. But the male Pernyi
paired readily with the female Roylei. I obtained six such pairings, and
a large quantity of fertile ova. The pairings of Roylei (female) with
Pernyi (male) took place as follows: two on the 21st of May, one on the
3d of June, two on the 4th of June, and one on the 6th.

The larvae of this new hybrid, _Roylei-Pernyi_, contrary to what might
have been expected, were much easier to rear than those of Roylei, and
the cocoons obtained are far superior to those of Roylei, in size,
weight, and richness of silk. The cocoon of my new hybrid has, like
Roylei, an envelope, but there is no space between this envelope and the
true cocoon inside. Therefore, this time, the crossing of two different
species (but, it must be added, two very closely allied species) has
produced a hybrid very superior, at least to one of the types, that of
Roylei. The cocoons of the hybrid _Roylei-Pernyi_ seem to me larger and
heavier than any Pernyi cocoons I have as yet seen.

The larvae of this new hybrid have been successfully reared in France,
in Germany, in Austria, and in the United States of North America. The
cocoons obtained by Herr L. Huessman, one of my German correspondents,
are remarkable for their size and beauty. The silk is silvery white.

I have seventeen cocoons of this hybrid species, which number may be
sufficient for its reproduction. But the question arises, "Will the
moths obtained from these cocoons be susceptible of reproduction?"

In my report on Lepidoptera for the year 1879, I stated, with respect to
hybrids and degeneracy, that hybrids had been obtained by the crossing
of _Attacus pernyi_ and _Attacus yama-mai_, but that, although the moths
(some of which may be seen in the Bethnal-green Museum) are large and
apparently perfect in every respect, yet these hybrids could not be
reproduced. It must be stated that these two species differ essentially
in one particular point. _Yama-mai_ hibernates in the _ovum_ state,
while Pernyi hibernates in the _pupa_ state. The hybrids hibernated in
the _pupa_ state. Roylei, as Pernyi, hibernates in the _pupa_ state.

In the November number, 1881, of "The Entomologist," Mr. W.F. Kirby,
of the British Museum, wrote an article having for its title,
"Hermaphrodite-hybrid Sphingidae," in which, referring to hybrids of
_Smerinthus ocellatus_ and _populi_, he says that hermaphroditism is the
usual character of such hybrids.

I extract the following passage from his article: "I was under the
impression that hermaphroditism was the usual character of these
hybrids; and it has suggested itself to my mind as a possibility, which
I have not, at present, sufficient data either to prove or to disprove,
that the sterility of hybrids in general (still a somewhat obscure
subject) may perhaps be partly due to hybridism having a tendency to
produce hermaphroditism."

Now, will the moths of new hybrid Roylei pernyi (which I expect will
emerge in May or June, 1882) have the same tendency to hermaphroditism
as has been observed with the hybrids obtained by the crossing of
_Smerinthus populi_ with _Sm. ocellatus_? I do not think that such will
be the case with the moths of the hybrid Roylei-pernyi, on account of
the close relationship of Roylei with Pernyi, but nothing certain can be
known till the moths have emerged. Here are the few notes taken on the
hybrid Roylei-pernyi: Ova commenced to hatch on the 12th of June; these
were from the pairing which had taken place on the 21st of May. Larvae,
black, with long white hairs. Second stage commenced on the 21st of
June. Larva, of a beautiful green; tubercles orange-yellow; head dark
brown. Third stage commenced on the 1st of July; fourth stage on the
7th. Larva of same color in those stages; tubercles on the back,
violet-blue or mauve; tubercles on the sides, blue. Fifth stage
commenced on the 18th of July. Larva, with tubercles on back and sides,
blue, or violet-blue. First cocoon commenced on the 10th of August. Want
of time prevented me from taking fuller and more accurate notes.

_Attacus Atlas_.--For the first time, as stated before, I attempted the
rearing of a small number of Atlas larvae in the open air on the ailantus
tree, but had to remove the last two remaining larvae in September; the
others had all disappeared in consequence of the heavy and incessant
rains. These larvae were from eggs sent to me by one of my German
correspondents. The pairing of the moths had taken place on the 17th of
July, and the eggs had commenced to hatch on the 4th of August.

I had about eighty cocoons of another and larger race of Atlas imported
from the Province of Kumaon, but only eight moths emerged at intervals
from the 31st of July to the 30th of September. Not only did the moths
emerge too late in the season, but there never was a chance of obtaining
a pairing. In my report on Indian silkworms, published in the November
number of the "Bulletin de la Societe d'Acclimatation," for the year
1881, compiled from the work of Mr. J. Geoghegan, I reproduce the first
appendix of Captain Thomas Hutton to Mr. Geoghegan's work, in which are
given the names of all the Indian silkworms known by him up to the year
1871.

Of _Attacus atlas_, Captain Hutton says: "It is common at 5,500 feet at
Mussoorie, and in the Dehra Doon; it is also found in some of the deep
warm glens of the outer hills. It is also common at Almorah, where the
larva feeds almost exclusively upon the 'Kilmorah' bush or _Berberis
asiatica_; while at Mussoorie it will not touch that plant, but feeds
exclusively upon the large milky leaves of _Falconeria insignis_.
The worm is, perhaps, more easily reared than any other of the wild
bombycidae."

I will now quote from letters received from one of my correspondents in
Ceylon, a gentleman of great experience and knowledge in sericulture.

In a letter dated 24th August, 1881, my correspondent says: "The Atlas
moth seems to be a near relation of the Cynthia, and would probably feed
on the Ailantus. Here it feeds on the cinnamon and a great number of
other trees of widely different species; but the tree on which I
have kept it most successfully in a domestic state is the _Milnea
roxburghiana_, a handsome tree, with dark-green ternate leaves, which
keep fresh long after being detached from the tree. I do not think the
cocoon can ever be reeled, as the thread usually breaks when it comes
to the open end. I have tried to reel a great many Atlas cocoons, but
always found the process too tedious and troublesome for practical use.

"The Mylitta (Tusser) is a more hardy species than the Atlas, and I have
had no difficulty in domesticating it. Here it feeds on the cashew-nut
tree, on the so-called almond of this country (_Terminalia catappa_),
which is a large tree entirely different from the European almond, and
on many other trees. Most of the trees whose leaves turn red when about
to fall seem to suit it, but it is not confined to these. In the case of
the Atlas moth, I discovered one thing which may be well worth knowing,
and that was, that with cocoons brought to the seaside after the larvae
had been reared in the Central Provinces, in a temperature ten or twelve
degrees colder, the moths emerged in from ten to twenty days after the
formation of the cocoon. The duration of the _pupa_ stage in this, and
probably in other species, therefore, depends upon the temperature in
which the larvae have lived, as well as the degree of heat in which the
cocoons are kept; and in transporting cocoons from India to Europe, I
think it will be found that the moths are less liable to be prematurely
forced out by the heat of the Red Sea when the larvae have been reared in
a warm climate than when they have been reared in a cold one.

"I do not agree with the opinion expressed in one of your reports, that
the short duration of the larva stage, caused by a high temperature, has
the effect of diminishing the size of the cocoons, because the Atlas
and Tusser cocoons produced at the sea-level here are quite as large as
those found in the Central Provinces at elevations of three thousand
feet or more. According to the treatise on the "Silk Manufacture," in
"Lardner's Cyclopedia," the Chinese are of opinion that one drachm
of mulberry silkworms' eggs will produce 25 ounces of silk if the
caterpillars attain maturity within twenty-five days; 20 ounces if the
commencement of the cocoons be delayed until the twenty-eighth day; and
only 10 ounces if it be delayed until between the thirtieth and fortieth
day. If this is correct, a short-lived larva stage must, instead of
causing small cocoons, produce just the contrary effect."

In another letter, dated November 25, 1881, my correspondent says: "I am
sorry that you have not had better success in the rearing of your
larvae, but you should not despair. It is possible that the choice of an
improper food-plant may have as much to do with failures as the coldness
and dampness of the English climate. I lost many thousands of Atlas
caterpillars before I found out the proper tree to keep them on in a
domesticated state; and when I did attain partial success, I could
not keep them for more than one generation, till I found the _Milnea
roxburghiana_ to be their proper food plant. I do not know the proper
food-plant of the Mylitta (Tusser), but I have succeeded very well with
it, as it is a more hardy species than the Atlas. Though a Bombyx be
polyphagous in a state of nature, yet I think most species have a tree
proper to themselves, on which they are more at home than on any
other plant. I should like, if you could find out from some your
correspondents in India, on what species of tree Mylitta cocoons are
found in the largest numbers, and what is about the greatest number
found on a single tree. The Mylitta is common enough here, but there
does not seem to be any kind of tree here on which the cocoons are to be
found in greater numbers than twos and threes; and there must be some
tree in India on which the cocoons are to be found in much greater
plenty, because they could not otherwise be collected in sufficient
quantity for manufacturing purposes. The Atlas is here found on twenty
or more different kinds of trees, but a hundred or a hundred and fifty
cocoons or larvae may be found on a single tree of _Milnea roxburghiana_,
while they are to be found only singly, or in twos and threes, on any
other tree that I know of. The Atlas and Mylitta seem to be respectively
the Indian relations of the Cynthia and Pernyi. It is, therefore,
probable that the Ailantus would be the most suitable European tree for
the Atlas, and the oak for the Mylitta."

_Attacus mylitta_ (_Antheraea paphia_).--I did not receive a single
cocoon of this species for the season 1881. My stock consisted of seven
cocoons, from the lot received from Calcutta at the end of February,
1880. Five were female, and two male cocoons; one of the latter died,
thus reducing the number to six. The moths emerged as follows: One
female on the 21st of June, one female on the 26th, one female on the
28th, one female on the 1st of July, and one male on the 3d of August;
the latter emerging thirty-four days too late to be of any use for
rearing purposes. The last female moth emerged, I think, about the end
of September. These cocoons had hibernated twice, as has been the case
with other Indian species. I had Indian cocoons which hibernated even
three times.

_Attacus cynthia_, from the province of Kumaon.--With the Atlas cocoons,
a large quantity of Cynthia cocoons were collected in the province
of Kumaon. Both species had, no doubt, fed on the same trees; as the
Cynthia, like the Atlas cocoons, were all inclosed in leaves of the
_Berberis vulgaris_, which shows that Cynthia is also a polyphagous
species. It is already known that it feeds on several species of trees,
besides the ailantus, such as the laburnum, lilac, cherry, and, I think,
also on the castor-oil plant; the common barberry has, therefore, to be
added to the above food plants.

These Kumaon Cynthia cocoons were somewhat smaller and much darker in
color than those of the acclimatized Cynthia reared on the ailantus. The
moths of this wild Indian Cynthia were also of a richer color than those
of the cultivated species in Europe.

During the summer 1881, I saw cocoons of my own Cynthia race obtained
from worms which had been reared on the laburnum tree. These cocoons
were, as far as I can remember, of a yellowish or saffron color; which
I had never seen before. This difference in the color of the cocoon was
very likely produced by the change of food, although it has been stated,
and I think it may be quite correct, that with many species of native
lepidoptera the change of food-plants does not produce any difference of
color in the insects obtained. With respect to the Cynthia worms reared
on the laburnum instead of the ailantus, it may be that the moths, which
will emerge from the yellow cocoons, will be similar to those obtained
from cocoons spun by worms bred on the ailantus, and that the only
difference will be in the color of the cocoons.

The Kumaon Cynthia cocoons, as I found it to be the case with Indian
species introduced for the first time into Europe, did not produce moths
at the same time, nor as regularly as the acclimatized species. The
moths emerged as follows: One female on the 22d of July; one female on
the 25th; one male on the 3d August; one female on the 19th; one male on
the 28th of August; one male on the 2d September; one female on the 3d.
A pairing was obtained with the latter two. Two males emerged on the 4th
of September; one male on the 6th; one male and one female on the 22d;
one female on the 23d; and one female on the 25th of September. Five
cocoons, which did not produce any moths, contain pupae, which are still
in perfect condition; and the moths will no doubt emerge next summer
(1882). As seen in my note, a pairing of this wild Indian Cynthia took
place; this was from the evening of the 4th to the 5th of September. The
eggs laid by the female moth were deposited in a most curious way, in
smaller or larger quantities, but all forming perfect triangles. These
eggs I gave to a florist who has been very successful in the rearing
of silk-producing and other larvae; telling him to rear the Cynthia on
lilacs grown in pots and placed in a hot-house, which was done. The
worms, which hatched in a few days, as they were placed in a hot-house,
thrived wonderfully well, and I might say they thrived too well, as they
grew so fast and became so voracious that the growth of the lilac trees
could not keep pace with the growth of the worms. These, at the fourth
stage, became so large that the foliage was entirely devoured, and, of
course, the consequence was that all the worms were starved. I only
heard of the result of that experiment long after the death of the
larvae; otherwise I should have suggested the use of another plant after
the destruction of the foliage of the lilacs; the privet (_Ligustrum
vulgare_) might have been tried, and success obtained with it.

Of such species as _Attacus pyri_, of Central Europe, and _Attacus
pernyi_, the North Chinese oak silkworm, which I have mentioned in my
previous reports, and bred every season for several years, I shall only
say that I never could rear Pyri in the open air in London, up to the
formation of the cocoon. As to Pernyi, I had, in 1881, an immense
quantity of splendid moths, from which I obtained the largest quantity
of ova I ever had of this species. I had many thousands of fertile ova
of Pernyi, which I was unable to distribute. Many schoolboys reared
Pernyi worms, but with what success I do not yet know. The number of
fertile ova obtained from Pyri moths was also more considerable than in
former years, which was due partly to the good quality of the pupae, and
partly to the very favorable weather in June, at the time the pairings
of the moths took place.

Leaving these, I now come to the North American species.

_Telea polyphemus_.--As I have stated in former years, this is the best
North American silkworm, producing a closed cocoon, somewhat smaller
than that of Pernyi, but the silk seems as good as that of Pernyi.

The cocoons of Polyphemus I had in 1881 were smaller and inferior in
quality to those I had before. Those received in 1878 and 1879 were
considerably finer and larger than those which were sent in 1880 and
1881; besides, they were sent in much larger quantities. The cocoons
received this year (1882) are finer than those of 1881, but yet they
cannot be compared with those of 1878 and 1879.

With about sixty cocoons of _Telea polyphemus_ I only obtained three
pairings, which I attribute solely to the weakness of the moths, as
the weather was all that could be desired for the pairings. The moths
emerged from the 1st of June to the 20th of July. One male moth emerged
on the 7th September. This latter was one from a small number of cocoons
received from Alabama; the other cocoons of the same race had emerged at
the same time as the cocoons from the Northern States. In the Northern
States the species is single-brooded; in the Southern States it is
double-brooded.

The larvae of Polyphemus can be bred in the open air in England, almost
as easily as those of Pernyi, and even Cynthia; they will pass through
their five stages and spin their cocoons on the trees, unless the
weather should be unexceptionally cold and wet, as was the case during
the month of August, 1881, when the larvae had reached their full size;
they were reared this year on the nut-tree, and some on the oak. The
species is extremely polyphagous, and will feed well on oak, birch,
chestnut, beech, willow, nut, etc.

The moth of Polyphemus is very beautiful, and, as in some other species,
varies in its shades of color. The larva is of a transparent green, of
extreme beauty; the head is light brown; without any black dots, as in
Pernyi; the spines are pink, and at the base of each of them there is a
brilliant metallic spot. When the sun shines on them the larvae seem to
be covered with diamonds. These metallic spots at the base of the spines
are also seen on Pernyi, Yama mai, Mylitta, and other species of the
genus Antheraea, all having a closed cocoon, but none of these have so
many as Polyphemus.

The cocoons of the species of the genus Actias are closed, but the larvae
have not the metallic spots of the species of the genus Antheraea.

_Samia Gloveri_.--Three North American silk-producing bombyces, very
closely allied, have been mentioned in my previous reports; they are;
_Samia ceanothi_, from California; _Samia gloveri_, from Utah and
Arizona; and _Samia cecropia_, commonly found in most of the Northern
States--the latter is the best and largest silk producer. Crossings of
these species took places in 1880, and, as I stated before, the ova
obtained from a long pairing between a Ceanothi female with a Gloveri
male, were the only ones which were fertile. The Gloveri cocoons
received in 1880 were of a very inferior quality, and produced moths
from which no pairings could be obtained, although some crossings took
place. In 1881, the Gloveri cocoons, on the contrary, produced fine,
healthy moths; yet only five pairings could be obtained, with about one
hundred cocoons. Besides these five pairings, a quantity of fertile
ova were obtained by the crossings of _S. gloveri_ (female) with _S.
cecropia_ (male), and Cecropia (female) with Gloveri (male). No success,
so far as I know, was obtained with the rearing of the hybrid larvae; the
rearings of the larvae of pure Gloveri were also, I think, a failure,
only one correspondent having been successful; but some correspondents
have not yet made the result of their experiments known to me. The larvae
of _Samia cecropia, S. gloveri_, and _S. ceanothi_, are very much alike;
and hardly any difference can be observed in the first two stages. In
the third and fourth stages, the larvae of _S. cecropia_ and _S. gloveri_
are also nearly alike; the principal difference between these two
species and _S. cecropia_ being that the tubercles on the back are of a
uniform color--orange-red, or yellow--while on Cecropia the first four
dorsal tubercles are red, and the rest yellow. The tubercles on the
sides are blue on the three species.

The larvae of the hybrids _Gloveri-cecropia_ were, as far as I could
observe, like those of Cecropia, but I noticed some with six red
tubercles on the back instead of four, as on Cecropia. They were reared
on plum, apple, and _Salix caprea_; in the open air.

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