A FEW WORDS ABOUT MOTHS.
The butterflies and moths from their beauty and grace, have always been
the favorites among amateur entomologists, and rare and costly works
have been published in which their forms and gorgeous colors are
represented in the best style of natural history art. We need only
mention the folio volume of Madam Merian of the last century, Harris's
Aurelian, the works of Cramer, Stoll, Drury, Hübner, Horsfield,
Doubleday and Westwood, and Hewitson, as comprising the most luxurious
and costly entomological works.
Near the close of the last century, John Abbot went from London and
spent several years in Georgia, rearing the larger and more showy
butterflies and moths, and painting them in the larva, chrysalis and
adult, or imago stage. These drawings he sent to London to be sold. Many
of them were collected by Sir James Edward Smith, and published under
the title of "The Natural History of the Rarer Lepidopterous Insects of
Georgia, collected from the Observations of John Abbot, with the Plants
on which they Feed." (London, 1797. 2 vols., fol.) Besides these two
rare volumes there are sixteen folio volumes of drawings by Abbot in the
Library of the British Museum. This work is of especial interest to the
American student as it illustrates the early stages of many of our
butterflies and moths.
Indeed the study of insects possesses most of its interest when we
observe their habits and transformations. Caterpillars are always to be
found, and with a little practice are easy to raise; we would therefore
advise any one desirous of beginning the study of insects to take up the
butterflies and moths. They are perhaps easier to study than any other
group of insects, and are more ornamental in the cabinet. As a
scientific study we would recommend it to ladies as next to botany in
interest and in the ease in which specimens may be collected and
examined. The example of Madam Merian, and several ladies in this
country who have greatly aided science by their well filled cabinets,
and critical knowledge of the various species and their transformations,
is an earnest of what may be expected from their followers. Though the
moths are easy to study compared with the bees, flies, beetles and bugs,
and dragon flies, yet many questions of great interest in philosophical
entomology have been answered by our knowledge of their structure and
mode of growth. The great works of Herold on the evolution of a
caterpillar; of Lyonet on the anatomy of the Cossus; of Newport on that
of the Sphinx; and of Siebold on the parthenogenesis of insects, are
proofs that the moths have engaged the attention of some of the master
minds in science.
The study of the transformations of the moths is also of great
importance to one who would acquaint himself with the questions
concerning the growth and metamorphoses and origin of animals. We should
remember that the very words "metamorphosis" and "transformation," now
so generally applied to other groups of animals and used in
philosophical botany, were first suggested by those who observed that
the moth and butterfly attain their maturity only by passing through
wonderful changes of form and modes of life.
The knowledge of the fact that all animals pass through some sort of a
metamorphosis is very recent in physiology. Moreover the fact that these
morphological eras in the life of an individual animal accord most
unerringly with the gradation of forms in the type of which it is a
member, was the discovery of the eminent physiologist Von Baer. Up to
this time the true significance of the luxuriance and diversity of
larval forms had never seriously engaged the attention of systematists
in entomology.
What can possibly be the meaning of all this putting on and taking off
of caterpillar habiliments, or in other words, the process of moulting,
with the frequent changes in ornamentation, and the seeming
fastidiousness and queer fancies and strange conceits of these young and
giddy insects seems hidden and mysterious to human observation. Indeed,
few care to spend the time and trouble necessary to observe the insect
through its transformations; and that done, if only the larva of the
perfect insect can be identified and its form sketched how much was
gained! A truthful and circumstantial biography, in all its relations,
of a single insect has yet to be written!
We should also apply our knowledge of the larval forms of insects to the
details of their classification into families and genera, constantly
collating our knowledge of the early stages with the structural
relations that accompany them in the perfect state.
The simple form of the caterpillar seems to be a concentration of the
characters of the perfect insect, and presents easy characters by which
to distinguish the minor groups; and the relative rank of the higher
divisions will only be definitely settled when their forms and methods
of transformation are thoroughly known. Thus, for example, in two groups
of the large Attacus-like moths, which are so amply illustrated in Dr.
Harris's "Treatise on Insects injurious to Vegetation"; if we take the
different forms of the caterpillars of the Tau moth of Europe, which are
figured by Duponchel and Godard, we find that the very young larva has
four horn-like processes on the front, and four on the back part of the
body. The full grown larva of the Regalis moth, of the Southern and
Middle states, is very similarly ornamented. It is an embryonic form,
and therefore inferior in rank to the Tau moth. Multiply these horns
over the surface of the body, lessen their size, and crown them with
hairs, and we have our Io moth, so destructive to corn. Now take off the
hairs, elongating and thinning out the tubercles, and make up the loss
by the increased size of the worm, and we have the caterpillar of our
common Cecropia moth. Again, remove the naked tubercles almost wholly,
smooth off the surface of the body, and contract its length, thus giving
a greater convexity and angularity to the rings, and we have before us
the larva of the stately Luna moth that tops this royal family. Here are
certain criteria for placing these insects before our minds in the order
that nature has placed them. We have certain facts for determining which
of these three insects is highest and which lowest in the scale, when we
see the larva of the Luna moth throwing off successively the Io and
Cecropia forms to take on its own higher features. So that there is a
meaning in all this shifting of insect toggery.
This is but an example of the many ways in which both pleasure and
mental profit may be realized from the thoughtful study of caterpillar
life.
In collecting butterflies and moths for cabinet specimens, one needs a
gauze net a foot and a half deep, with the wire frame a foot in
diameter; a wide-mouthed bottle containing a parcel of cyanide of
potassium gummed on the side, in which to kill the moths, which should,
as soon as life is extinct, be pinned in a cork-lined collecting box
carried in the coat pocket. The captures should then be spread and dried
on a grooved setting board, and a cabinet formed of cork-lined boxes or
drawers; as a substitute for cork, frames with paper tightly stretched
over them may be used, or the pith of corn-stalks or palm wood.
Caterpillars should be preserved in spirits, or in glycerine with a
little alcohol added.
Some persons ingeniously empty the skins and inflate them over a flame
so that they may be pinned by the side of the adult.
Some of the most troublesome and noxious insects are found among the
moths. I need only mention the canker worm and American tent
caterpillar, and the various kinds of cut worms, as instances.
[Illustration: 43. Parasite of the American Silk Worm.]
We must not, however, forget the good done by insects. They undoubtedly
tend by their attacks to prevent an undue growth of vegetation. The
pruning done to a tree or herb by certain insects undoubtedly causes a
more healthy growth of the branches and leaves, and ultimately a greater
production fruit. Again, as pollen-bearers, insects are a most powerful
agency in nature. It is undoubtedly the fact that the presence, of bees
in orchards increases the fruit crop, and thus the thousands of moths
(though injurious as caterpillars), wild bees and other insects, that
seem to live without purpose, are really, though few realize it, among
the best friends and allies of man.
Moreover, insects are of great use as scavengers; such are the young or
maggots of the house fly, the mosquitoes, and numerous other forms, that
seem created only to vex us when in the winged state. Still a larger
proportion of insects are directly beneficial from their habit of
attacking injurious species, such as the ichneumons (Fig. 43, the
ichneumon of the American silk worm) and certain flies (Fig. 44,
Tachina); also many carnivorous species of wasps beetles and flies,
dragon flies and Aphis lions (Fig. 45, the lace-winged fly; adult, larva
and eggs).
[Illustration: 44. Tachina, parasite of Colorado Potato Beetle.]
[Illustration: 45. The Lace-winged Fly, Its Larva and Eggs.]
But few, however, suspect how enormous are the losses to crops in this
country entailed by the attacks of the injurious species. In Europe, the
subject of applied entomology has always attracted a great deal of
attention. Most sumptuous works, elegant quartos prepared by naturalists
known the world over, and published at government expense, together with
smaller treatises, have frequently appeared; while the subject is taught
in the numerous agricultural colleges and schools, especially of
Germany.
In the densely populated countries of Europe, the losses occasioned by
injurious insects are most severely felt, though from many causes, such
as the greater abundance of their insect parasites, and the far greater
care taken by the people to exterminate their insect enemies, they have
not proved so destructive as in our own land.
In this connection I may quote from one of Dr. Asa Fitch's reports on
the noxious insects of New York, where he says: "I find that in our
wheat-fields here, the midge formed 59 per cent. of all the insects on
this grain the past summer; whilst in France, the preceding summer, only
7 per cent. of the insects on wheat were of this species. In France the
parasitic destroyers amounted to 85 per cent.; while in this country our
parasites form only 10 per cent."
"A true knowledge of practical entomology may well be said to be in its
infancy in our own country, when, as is well-known to agriculturists,
the cultivation of wheat has almost been given up in New England, New
York, Pennsylvania, Ohio and Virginia, from the attacks of the wheat
midge, Hessian fly, joint worm, and chinch bug. According to Dr.
Shimer's estimate, says Mr. Riley, in his Second Annual Report on the
Injurious Insects of Missouri, which may be considered a reasonable
one, in the year 1864 three-fourths of the wheat, and one-half of the
corn crop were destroyed by the chinch bug throughout many extensive
districts, comprising almost the entire North-West. At the annual rate
of increase, according to the United States Census, in the State of
Illinois, the wheat crop ought to have been about thirty millions of
bushels, and the corn crop about one hundred and thirty-eight million
bushels. Putting the cash value of wheat at $1.25, and that of corn at
50 cents, the cash value of the corn and wheat destroyed by this
insignificant little bug, no bigger than a grain of rice, in one single
State and one single year, will therefore, according to the above
figures, foot up to the astounding total of _over seventy-three millions
of dollars_!"
The imported cabbage butterfly (Pieris rapæ), recently introduced from
Europe, is estimated by the Abbé Provatncher, a Canadian entomologist,
to destroy annually two hundred and forty thousand dollars' worth of
cabbages around Quebec. The Hessian fly, according to Dr. Fitch,
destroyed fifteen million dollars' worth of wheat in New York State in
one year (1854). The army worm of the North (Leucania unipuncta), which
was so abundant in 1861, from New England to Kansas, was reported to
have done damage that year in Eastern Massachusetts exceeding half a
million of dollars. The joint worm (Isosoma hordei) alone sometimes cuts
off whole fields of grain in Virginia and northward. The Colorado potato
beetle is steadily moving eastward, now ravaging the fields in Indiana
and Ohio, and only the forethought and ingenuity in devising means of
checking its attacks, resulting from a thorough study of its habits,
will deliver our wasted fields from its direful assaults.
These are the injuries done by the more abundant kinds of insects
injurious to crops. We should not forget that each fruit or shade tree,
garden shrub or vegetable, has a host of insects peculiar to it, and
which, year after year, renew their attacks. I could enumerate upwards
of fifty species of insects which prey upon cereals and grass, and as
many which infest our field crops. Some thirty well known species ravage
our garden vegetables. There are nearly fifty species which attack the
grape vine, and their number is rapidly increasing. About seventy-five
species make their annual onset upon the apple tree, and nearly an equal
number may be found upon the plum, pear, peach and cherry. Among our
shade trees, over fifty species infest the oak; twenty-five the elm;
seventy-five the walnut, and over one hundred species of insects prey
upon the pine.
Indeed, we may reasonably calculate the annual loss in our country
alone, from noxious animals and the lower forms of plants, such as rust,
smut and mildew, as (at a low estimate) not far from five hundred
million dollars annually. Of this amount, at least one-tenth, or fifty
million dollars, could probably be saved by human exertions.
To save a portion of this annual loss of food stuffs, fruits and lumber,
should be the first object of farmers and gardeners. When this saving is
made, farming will become a profitable and safe profession. But while a
few are well informed as to the losses sustained by injurious insects,
and use means to ward off their attacks, their efforts are constantly
foiled by the negligence of their neighbors. As illustrated so well by
the history of the incursions of the army worm and canker worm, it is
only by a combination between farmers and orchardists that these and
other pests can be kept under. The matter can be best reached by
legislation. We have fish and game laws; why should we not have an
insect law? Why should we not frame a law providing that farmers, and
all owning a garden or orchard, should cooperate in taking preventive
measures against injurious insects, such as early or late planting of
cereals, to avert the attacks of the wheat midge and Hessian fly; the
burning of stubble in the autumn and spring to destroy the joint worm;
the combined use of proper remedies against the canker worm, the
various cut worms, and other noxious caterpillars? A law carried out by
a proper State entomological constabulary, if it may be so designated,
would compel the idle and shiftless to clear their farms and gardens of
noxious animals.
[Illustration: 46. Pickle Worm and its Moth.]
Among some of the injurious insects reported on by Mr. Riley, the State
Entomologist of Missouri, is a new pest to the cucumber in the West, the
Pickle worm (Phacellura nitidalis, Fig. 46). This is a caterpillar which
bores into the cucumbers when large enough to pickle, and which is
occasionally found in pickles. Three or four worms sometimes occur in a
cucumber, and in the garden a single one will cause it to rot. One of
the most troublesome intruders in our graperies is the Vine dresser
(Choerocampa pampinatrix, Fig. 47, larva and pupa; Fig. 48, adult), a
single caterpillar of which will sometimes "strip a small vine of its
leaves in a few nights," and occasionally nips off bunches of half-grown
grapes.
[Illustration: 48. Vine Dresser Moth.
47. Vine Dresser and Chrysalis.]
Another caterpillar, which is sometimes so abundant as nearly to
defoliate the grape vine, is the eight spotted Alypia (Fig. 49; _a_,
larva; _b_, side view of a segment). This must not be confounded with
the bluish larva of the Wood Nymph, Eudryas grata (Fig. 50), which
differs from the Alypia caterpillar in being bluish, and in wanting the
white patches on the side of the body, and the more prominent hump on
the end of the body. Another moth (Psychomorpha epimenis, Fig. 51,
_a_, larva; _b_, side view of a segment; _c_, top view of the hump),
also feeds on the grape, eating the terminal buds. It is also bluish,
and wants the orange bands on the side of the body. Another moth of this
family is the American Procris (Acoloithus Americana, Fig. 52_a_, larva;
_b_, pupa; _c_, cocoon; _d_, _e_, imago); a dark blue moth, with a deep
orange collar, whose black and yellow caterpillar is gregarious (Fig.
53), living in companies of a dozen or more and eating the softer parts
of the leaves. It is quite common in the Western and Southern States.
The figure represents two separate broods of caterpillars feeding on
either side of the midrib of the leaf. But if the moths are, as a rule,
the enemies of our crops, there are the silk worms of the East and
Southern Europe and California, which afford the means of support to
multitudes of the poorer classes, and supply one of the most valuable
articles of clothing. Blot out the silk worm, and we should remove one
of the most important sources of national wealth, the annual revenue
from the silk trade of the world amounting to $254,500,000.
[Illustration: 49. Eight-spotted Alypia and Larva.]
[Illustration: 50. Eudryas grata.]
[Illustration: 51. Larva of Psychomorpha.]
[Illustration: 52. American Procris and Young.]
[Illustration: 53. Larvæ of American Procris.]
Silk culture is rapidly assuming importance in California, and though
the Chinese silk worm has not been successfully cultivated in the
Eastern States, yet the American silk worm, Teleas Polyphemus (see
frontispiece, male; Fig. 54, larva; 55, pupa; 56, cocoon), can, we are
assured by Mr. Trouvelot, be made a source of profit.
This is a splendid member of the group of which the gigantic Attacus
Atlas of China is a type. It is a large, fawn colored moth with a tawny
tinge; the caterpillar is pale green, and is of the size indicated in
the cut. Mr. Trouvelot says that of the several kinds of silk worms, the
larva of the present species alone deserves attention. The cocoons of
Platysamia Cecropia may be rendered of some commercial value, as the
silk can be carded, but the chief objection is the difficulty of raising
the larva.
"The Polyphemus worm spins a strong, dense, oval cocoon, which is closed
at each end, while the silk has a very strong and glossy fibre." Mr.
Trouvelot, from whose interesting account in the first volume of the
"American Naturalist" we quote, says that in 1865 "not less than a
million could be seen feeding in the open air upon bushes covered with a
net; five acres of woodland were swarming with caterpillar life." The
bushes were scrub oaks, the worms being protected by a net. After
meeting with such great success Mr. Trouvelot lost all his worms by
pebrine, the germs being imported in eggs received from Japan through M.
Guérin-Méneville of Paris. Enough, however, was done to prove that silk
raising can be carried on profitably, when due precautions are taken, as
far north as Boston. As this moth extends to the tropics, it can be
reared with greater facility southwards. The cocoon is strong and dense,
and closed at each end, so that the thread is continuous, while the silk
has a very strong and glossy fibre.
[Illustration: 54. American Silk Worm.]
Next in value to the American silk worm, is the Ailanthus silk worm
(Samia Cynthia) a species allied to our Callosamia Promethea. It
originated from China, where it is cultivated, and was introduced into
Italy in 1858, and thence spread into France, where it was introduced by
M. Guérin-Méneville. Its silk is said to be much stronger than the fibre
of cotton, and is a mean between fine wool and ordinary silk. The worm
is very hardy, and can be reared in the open air both in this country
and in Europe. The main drawback to its culture is the difficulty in
unreeling the tough cocoon, and the shortness of the thread, the cocoon
being open at one end.
The Yama-maï moth (Antheræa Yama-maï) was introduced into France from
Japan in 1861. It is closely allied to the Polyphemus moth, and its
caterpillar also feeds on the oak. Its silk is said to be quite
brilliant, but a little coarser and not so strong as that of the Bombyx
mori. The Perny silk worm is extensively cultivated by the Chinese in
Manchouria, where it feeds on the oak. Its silk is coarser than that of
the common silk worm, but is yet fine, strong and glossy. Bengal has
furnished the Tussah moth, which lives in India on the oak and a variety
of other trees. It is largely raised in French and English India,
according to Nogués, and is used in the manufacture of stuffs called
corahs.
[Illustration: 55. Chrysalis of American Silk Worm.]
[Illustration: 56. Cocoon of American Silk Worm.]
The last kind of importance is the Arrhindy silk worm, from India. It
has been naturalized in France and Algeria by M. Guérin-Méneville, who
has done so much in the application of entomology to practical life. It
is closely allied to the Cynthia or Ailanthus worm, with the same kind
of silk and a similar cocoon, and feeds on the castor oil plant.
The diseases of silk worms naturally receive much attention. Like those
afflicting mankind, they arise from bad air, resulting from too close
confinement, bad food, and other adverse causes. The most fatal and
wide-spread disease, and one which since 1854 has threatened the
extermination of silk worms in Europe, is the _pebrine_. It is due to
the presence of minute vegetable corpuscles, which attack both the worms
and the eggs. It was this disease which swept off thousands of Mr.
Trouvelot's Polyphemus worms, and put a sudden termination to his
important experiments, the germs having been implanted in eggs of the
Yama-maï moth imported from Japan by M. Guérin-Méneville, and which were
probably infected as they passed through Paris. Though the disaster
happened several years since, he tells us that it will be useless for
him to attempt the raising of silk worms in the town where his
establishment is situated, as the germs of the disease are most
difficult to eradicate.
So direful in France were the ravages of this disease that two of the
most advanced naturalists in France, Quatrefages and Pasteur, were
commissioned by the French government to investigate the disease.
Pasteur found that the infected eggs differed in appearance from the
sound ones, and could thus be sorted out by aid of the microscope and
destroyed. Thus these investigations, carried on year after year, and
seeming to the ignorant to tend to no practical end, resulted in saving
to France her silk culture. During the past year (1871) so successful
has his method proved that a French scientific journal expresses the
hope of the complete reestablishment and prosperity of this great
industry. A single person who obtained in 1871 in his nurseries 30,000
ounces of eggs, hopes the next year to obtain 100,000 ounces, from which
he expects to realize about one million dollars.
[Illustration: The Potato Caterpillar.]