A. S. (Alpheus Spring) Packard.

Guide to the study of insects, and a treatise on those injurious and beneficial to crops: for the use of colleges, farm-schools, and agriculturists online

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Online LibraryA. S. (Alpheus Spring) PackardGuide to the study of insects, and a treatise on those injurious and beneficial to crops: for the use of colleges, farm-schools, and agriculturists → online text (page 22 of 29)
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with them are more
highly specialized
than in other in-
sects. Their fore

168 -

wings are usually

triangular in form,

while their hind

wings are some- Fi =- 169 - Fig. 170.

what square or rounded. The anterior wings are the most

typical in form and venation.

The surface, from the costa to the inner edge, may be


Fig. 171.

divided into three areas, the costal, median, and internal.
There are five principal veins : the costal and subcostal are


grouped together, and form the costa or front edge of the wing ;
the median occupies the middle of the wing; and the sulj-
nu'diMii and internal, the hinder, or internal, area of the wing.
Tin- c-ostal vein is usually simple, and joins the costa near its
outer third. The subcostal, near the middle of the wing, is
usually subdivided into five branches, which are called ven-
ules, while the median is usually subdivided into one venule
less, and the submedian and internal are simple. The last, or
fifth, subcostal venule, and the first median venule, generally
each throw out a small venule, which meet to form the discal
venule, thus enclosing a large central area called the discal area,
or cell. There are rarely any cross venules present. Some-
times, as in Hepialus, there is a transverse costal venule, and
an interno-submediaii venule. They are usually found only in
degraded Lepidoptera, and recall the net-veined style of vena-
tion of the Neuroptera.

The legs are slender, cylindrical, and weak. The COXOB are
closely united with the thorax, the trochanters are spherical,

FIGS. 155, 158, give a general view of the body of a butterfly denuded of scales.
FIG. l.~>5. a, antenna; l,prothorax; m, patagia, or shoulder-tippets; k, mesoscutum;
n, abdomen; A, costal edge of fore-wing; D, apex; C, outer edge excavated ;.E,
outer angle; B, inner edge; ab, discal cell; aw, discal venules, throwing off the
hull-pendent vein, aZ. The dotted lines indicate the inner, middle and outer third
of the wing. FIG. 157 illustrates the mode of ornamentation of the wings
of moths ; ab, am and al, the inner, the middle, and outer third of the wings. The
capitals are the same as in FIG. 155; sr7, the basal line; sa, the inner line; sp,
the outer, and ms, the marginal line variously waved, scalloped and anguhited.
In most of the Noctuidae are the dentiform spot, 1 b; mo, the orbicular, and mr, the
rcniform spots; between the two latter often runs the transverse shade, um. In
I-'n;. l.")S, hind wing, fr indicates the "bristle" which fits into the "hook" on
the fore- wing, uniting the two wings during flight; cm, situated in the discal cell,
indicates the "lunule," and beyond are the outer and marginal dusky bands.
FIG. 159, la, internal vein; 16, submedian vein; 2, 3, 4, 5, the four branches
(venules) of the median vein (in FIG. ICO, 5 becomes the independent venule);
6 to 12, branches of the subcostal (in FIG. 161, \i\, is the costo-subcostal recurrent
venule). In FIG. 1U2, wings of the Hepialus, the venation is moi-e irregular, and in
the fore-wing the discal cell is divided into an anterior and posterior discal
cellule, by the disco-longitudinal vein ; s(f, x, and s, accessory cells. In the Tineids
the venation is very simple. In FIG. 103, the submedian and internal veins have
disappeared; 9 is the costal vein; 2, 3, the two branches of the median vein; 4 to
8, branches of the subcostal vein. In FIG. 164, the internal vein is shortened, and tin-
submedian forked, while the median and subcostal are merged together. /'/<>//*
H - iii'-inann,in Morris's Synopsis, Smitlisonian Miscellaneous Collections, Compare
also FIG. 29 on pag<> _:;.

FIGS. 150 and 165. a, antenna, on one side wholly, and on the other partially,
pectinate; b, eye;/, ocellus; h, labial palpus; //, maxillic or "tongue;" o, coxa;
p, troch 'inter; </, femur; r, tibia; V, single anterior spur; r*, two middle tibial
spurs; 2, 3, two pairs of posterior tibial spurs; s, tarsus.


and the femora, tibiae and tarsi, slender and very equal in
length. There are usually two tibial spurs. The tarsus is
five-jointed, the terminal joint ending in two slender claws.

The scales covering the body of Lepidoptera are simply
modified hairs. In studying the wing of the Cecropia moth,
we find the hairs of the body and base of the wing gradually
passing into the forms represented in Fig. 16G. They are
attached to the wings and laid partially over one another like
the tiles on a roof (Fig. 167). They are inserted in somewhat
regular lines, though, as seen in the figure, these lines are often
irregular, as shown by the line of scars where the scales have
been removed. The scales are beautifully ornamented with mi-
croscopic lines. We find, on removing the scales, that the
head consists of three well-marked pieces,* i. e. the occiput
or basal piece which lies behind the ocelli ; the epicranium,
lying behind the insertion of the antennae, and earning the eyes
and ocelli, and the clypeus, which constitutes the front of the
head. The latter piece is larger than in all other insects, its
size being distinctive of the Lepidoptera. There is a general
form of this piece for each family, and it affords excellent
characters in the diiferent genera, especially among the butter-
flies (as Mr. L. Trouvelot has shown us in a series of drawings
made by him), and the Zygwnidce and Bombycidce. It is
largest, and most perfectly shield-shaped, in the Attaci. In the
Phalcenidce, it is smaller, and square; and in the Tine idee
it is smaller still, while the occiput and epicranium are

The labrum is remarkably small and often concealed by the
overhanging clypeus. The labium is small, short, triangular,
and the mentum is nearly obsolete. The lingua is obsolete, its
place being supplied by the tongue-like maxillae. The labial
palpi are feebly developed, sometimes rudimentary, and consist

*FiG. 168. A, head of Ctenucha Virginica denuded; oc, occiput; ec, epicranium,
with the two ocelli, o, and the base of the antenna;, at ; e, eye; c, clypeus; I, la-
brum; m, mandible: mx, tongue, or maxilla?, with the end split apart; B, rudimen-
tary maxilla of Actias Luna, with its single-jointed rudimentary palpus, showing
the mode of attachment to the base of the maxilla; C, two-jointed, rudimentary
labial palpus of A. Luna; D, the same, single jointed, of Platysamia Cecropia.

FIGS. 169, 170. Head of amoth in relation to the prothorax (1). FIG. 171, A, B, side
view and (C) front view of the head of a moth ; a, antenna ; b, eye ; rf, the " front ; "
e, orbit of the eye; /, ocellus; g, maxilla situated between h, the three-jointed la-
bial palpi ; i, the maxillary palpus, sometimes very large and three-jointed.



of from one to three joints, the terminal one being small and
pointed. They are recurved in front of the head, on each side 1
of the spiral tongue, and are
covered with hairs ; their func-
tion, as touchers or feelers,
seeming to be lost. The man-
dibles are rudimentary, consist-
ing of a pair of horny tubercles,
partly concealed by the front
edge of the clypeus. The
maxilla?, on the other hand,
are remarkably developed. In
their rudimentary state, as in Attacus, they form a pair of
grooved blades, the hollowed sides being opposed and held

Fig. 173. Fig. 174. Fig. 175.

together by a row of minute teeth, thus forming a canal. The
insect sucks through this long tube the sweets of flowers.

Fig. 176. Fig. 177. Fig. 178. Fig. 179.

The "tongue" is often nearly as long as the body of the insect
itself, and when at rest, is rolled up and held between the
palpi. At its base are the minute rudimental maxillary palpi,


which are generally concealed, but are apparent in the smaller
and lower moths, Crambus and the Tineids. They are usually
from two to three-jointed, and even five to six-jointed, as in
Tinea granella, and longer than the maxillae, thus resembling
the Pliryganeidce , or Caddis flies.

In seeking for honey with their long maxillae, the Lepidop-
tera play an important part in the fertilization of plants,
especially the Orchids.

The ocelli are often present, though they do not form a tri-
angle on the vertex, as there are onty two, the third and most
anterior one being absent. The eyes are large and globose,
and vary in their distance apart in different families.

The antennae vary greatly ; they are either filiform (Fig. 172,
a), or setiform (Fig. 172, 6), or fusiform, as in the Sphinges
(Fig. 172, c), or club-shaped, as in Papilio (Fig. 172, d). They
are rarely entirely naked, but are finely ciliated (Fig. 173), or
have a pair of bristles on each joint (Fig. 174), which are
sometimes tufted (Fig. 175). The joints are sometimes toothed
(Fig. 176), lamellate (Fig. 177), serrate (Fig. 178), or pec-
tinate (Fig. 179).

The thorax in Lepidoptera is remarkable for the small size
of the first, or prothoracic ring, the mesothorax being highly
developed. In Telea (Figs. 11 and 12, on page 11) the char-
acteristic form is well shown. The tergal arch of the pro-
thorax is almost obsolete, the scutum alone being represented
by a corneous piece, while the pleura! parts are more developed
as supports for the forelegs. In the mesothorax the prse-
scutum is present, but is usually vertical, being bent down
and concealed between the two rings, becoming visible, how-
ever, from above in Hepialus (Sthenopis), in which respect it
strikingly resembles the position and development of the same
piece in the neuropterous Polystcechotes. The scutum is large,
with convex sides, broadest behind the middle, and deeply
notched for the reception of the triangular scutellum, which
is about one-fourth the size of the scutum. The postscutellum
is transverse, and situated out of sight, unless the two hinder
thoracic rings are separated, under the scutellum. The, epi-
sterna and trochantines are large, and the whole mesothoracic
flanks nearly twice as wide as those of the metathorax. The


metathorax is much compressed antero-posteriorly. The scu-
tuni is thrown aside as it were by the scute-Hum into two lat-
eral, nearly square halves, the remaining tergal pieces being
usiKilly obsolete and membranous, but in Sthenopis the prse-
scuturn and scutellum (Fig. 13, page 12) are large, and meet
in the middle of the segment, much as in the neuropterous
Sialidce and Hemerobiidce.

The abdomen is oval in Papilio, becoming long and linear in
the Tineids. In the Zygcenidce, especially, the basal ring is
membranous and is partly adherent to the thorax, and somewhat
inflated on each side. The number of abdominal segments
varies, being either eight or nine ; the variation occurring, as
stated by Lacaze-Duthiers, in closely allied genera ; thus the
genital and anal openings are placed more usually behind the
eighth, but sometimes behind the ninth segment.

The genital armor is very simple, consisting of two valve-
like pieces. The parts beyond (anal stylets, etc.) are aborted,
so that the anus and external opening of the oviduct are
brought closely together. In the male the parts are more com-
plex, the anal forceps often, as in the Callosamia Promethea,
forming long curved hooks for clasping the abdomen of the

The nervous system of Lepidoptera, and its changes during
the transformations of the larva, have been studied most
thoroughly by Herold (in Pieris) and Newport (in Sphinx
ligustri and Vanessa urticse). In the imago the ventral cord
consists of seven ganglia, while in the larva there are eleven.
This decrease in their number is due to the fusion, during the
pupa state, of the first, second, third and fourth ganglia of
the larva, exclusive of those situated in the front part of the
head ; these form the two thoracic ganglia which distribute
nerves to the legs and the muscles of the wings. Meanwhile
the fifth and sixth ganglia of the larva have either disappeared
entirely, or been united with the others.

The digestive system (see Fig. 44, on page 35) of butterflies
and moths is modified to suit their peculiar habits. They dniw
in the sweets of plants through the "tongue" by a sucking
stomach which opens into the hinder end of the oesophagus.
14 The ileum is long, small, and nearly always forms several


convolutions. The colon is constantly of a large size, and is
often dilated into a caecum at its anterior portion." (Siebold.)
The salivary glands are composed of two simple tubes, which
are very large in the larval state, extending into the abdomen.

The respiratory system is normal and well developed. In
the larva the stigmata are wanting on the second and third
thoracic and last abdominal segment. In those species of
Spliingidoe, Bombycidce and Noctuidce, which have a
long-sustained flight there are numerous vesicular dilatations
of the tracheae .

The urinary tubes are six in number ; they are long, free,
and open into the stomach by two excretory ducts.

The silk-glands consist of two long, rlexuons, thick-walled
sacs, situated on the sides of the body, and opening by a
common orifice on the under lip (labium) usually at the
extremity of a short tubular protuberance (Siebold). They
are most developed when the larva approaches the pupa state.

We once found a larva of Clisiocampa Americana that had
just spun its cocoon, and to ascertain whether the silk had been
exhausted, we removed the worm from its cocoon, when it spun
another, but thinner one ; and upon removing it a second time
it spun a third very thin cocoon, before the supply of silk was
entirely exhausted.

The ovary consists of four very long, spiral, multilocular
tubes. The receptaculum seminis is pyriform, and often has a
long, spiral ductus seminalis. At its base is situated a large,
double sebaceous gland ; and there are two small ramose
glands, perhaps odoriferous, situated at the orifice of the vagina.
The copulatory pouch is a remarkably large, pyriform reservoir,
having for the reception of the male intromittent organ a
canal, which opens by a special orifice, situated below and
behind the external opening of the oviduct. (Siebold.)

The testes form two round or oval follicles, and the two
short deferent canals unite with two simple and very flexuous
accessory glands, to form the long ductus ejaculatorius.

Several interesting cases of hermaphroditism in butterflies
and moths have been published by European entomologists.
Mr. Edwards has noticed two remarkable instances in the Pro-
ceedings of the Philadelphia Entomological Society (vol. iv,


p. 3SO*), the latter of which we have also seen. "A specimen of
Papilio Asterias is in my collection, and was captured by Mr.
J. Meyer of Brooklyn, L. I., two or three years since. It is a
lint' instance of a perfect hermaphrodite. The right wings are
both male, the left wings both female, distinctly marked upon
both surfaces with no suffusion of color. The size is that of
the largest specimens of Asterias. The Saturnia Promethea
is in the collection of Mrs. Bridgham of New York, and is a
curious instance of an imperfect hermaphrodite. The left an-
tenna and left primary are male ; the right antenna and left
secondary are female ; the right primary is also female, but the
right secondary is something between the two, neither male
nor female. The color of the upper surface is nearly the same
as the under surface of the male. On the under side the
color and markings of the left primary are male, but the other
three wings are female. The color and markings of the male
Promethea are quite different from those of the female, and on
this hermaphrodite the confusion of the sexes is conspicuous.
It is a bred specimen. The body had been viscerated, so that it
is impossible to determine its sex."

The larva of Ctenucha, which resembles that of Arctia, con-
structs its cocoon out of the hairs of its body, without spinning
any silken threads, so far as we could ascertain by microscopi-
cal examination. The hairs of this, as of probably most hairy
caterpillars, but ' more especially the Bombycid larvae, arc
thickly armed with minute spinules, so that by being simply
placed next to each other, they readily adhere together. The
cocoon is finished in about twelve hours. We once noticed
a Ctenucha larva just beginning its cocoon. Early in the
morning it described an ellipse upon the side of the glass jar in
which it was confined, out of hairs plucked from just behind its
head. From this elliptical line as a base, it had by eight o'clock
built up, rather unequally, the walls of its cocoon, in some
places a third of the distance up, by simply piling upon each
other the spinulated hairs, which adhered firmly together. At
four o'clock in the afternoon, the arch was completed, and the
larva walled in by a light partition, and soon afterwards the thin
floor was made. No silk is spun throughout the whole opera-
tion, while in the cocoon of Pyrrharctia isabella there is a
slight frame-work of silk upon which the hairs are placed.


Trouvelot states that the Polyphemus larva constructs its
cocoon by drawing the leaves together as a support for the
threads, forming the foundation of the cocoon. "This seems
to be the most difficult feat for the worm to accomplish, as after
this the work is simply mechanical, the cocoon being made of
regular layers of silk united by a gummy substance. The silk
is distributed in zig-zag lines of about one-eight of an inch
long. When the cocoon is made, the worm will have moved
his head to and fro, in order to distribute the silk, about two
hundred and fifty-four thousand times. After about half a
day's work, the cocoon is so far completed that the worm can
hardly be distinguished through the fine texture of the wall ;
then a gummy, resinous substance, sometimes of a light brown
color, is spread over all the inside of the cocoon. The larva
continues to work for four or five days, hardly taking a few
minutes of rest, and finally another coating is spun in the
interior, when the cocoon is all finished and completely air-
tight. The fibre diminishes in thickness as the completion of
the cocoon advances, so that the last internal coating is not
half so thick and so strong as the outside ones."

In those moths which spin a thick cocoon, the pupa, a few
days previous to its exit, secretes an acid fluid from two glands
opening into the mouth. This fluid, according to Mr. L. Trou-
velot (American Naturalist, vol. i, p. 33), in his account of the
Polyphemus silk-worm, dissolves the hard gummy substance
uniting the silken threads, until after the expiration of half an
hour, the moth is able to push the fibres aside, and work its
way out, without breaking a thread.

Trouvelot says that the larvae of the Polyphemus moth (and
this remark will probably apply to all other Lepidopterous
larvae) seem entirely unable to discern objects with their sim-
ple ej^es, but can distinguish light from darkness.

In their adult state butterflies and moths take but little food,
consisting of honey, though Papilio Turnus, according to a
Canadian observer, is attracted to heaps of decaying fish.

Caterpillars grow very rapidly, and consume a great quantity
of food. Mr. Trouvelot gives us the following account of the
gastronomical powers of the Potyphemus caterpillar. "It is
astonishing how rapidly the larva grows, and one who has no
experience in the matter could hardly believe what an amount


of food is devoured by these little creatures. One experiment
which I made can give some idea of it : when the young silk
worm hatches out, it weighs one-twentieth of a grain ; when

10 days old it weighs 1-2 a grain, or 10 times its original weight.
20 " " " " 3 grains " 60 " " " "

30 " 31 620 " " " "

40 " " " " 90 " " 1800 " " " "

56 " " 207 " " 4140 " " " "

AVhcn a worm is thirty days old it will have consumed about
ninety grains of food ; but when fifty-six days old it is fully
grown and has consumed not less than one hundred and twenty
oak leaves weighing three-fourths of a pound ; besides this it
has drank not less than one-half an ounce of water. So the
food taken by a single silk-worm in fifty-six days equals in
weight eight}'-six thousand times the primitive weight of the
worm. Of this, about one-fourth of a pound becomes excre-
mentitious matter ; two hundred and seven grains are assimi-
lated and over five ounces have evaporated. What a destruction
of leaves this single species of insect could make if only a one
hundredth part of the eggs laid came to maturity ! A few
years would be sufficient for the propagation of a number large
enough to devour all the leaves of our forests." The Lepidop-
tera are almost without exception injurious to vegetation and
are among the chief enemies of the agriculturist.

They are rarely found fossil owing to the delicacy of their
bodies. Remains, doubtfully referred to the Lepidoptera, have
been found in the Jura formation. A Sphinx-like moth has
been discovered in the Tertiary formation of Europe, and a few
minute forms have occurred in Amber.

Butterflies are easily distinguished from the other groups by
their knobbed antennae. In the Sphinges and their allies the
feelers are thickened in the middle : in the Moths they are fili-
form and often pectinated like feathers. Lepidoptera have
also been 'divided into three large groups, called Diurnal, Cre-
puscular and Nocturnal, since butterflies fly in the sunshine
alone, most Sphinges in the twilight (some of them, however,
II v in the hottest sunshine), while the moths are generally
night-fliers, though many of them fly in the day time, thus
showing that the distinctions are somewhat artificial.

The larger Lepidoptera (butterflies and the larger moths)


have been called Macrolepidoptera, while the smaller ones,
including the smaller Pyralidce, the Tortricidce, and the
Tin ei dee, are called Microlepidoptera.

In studying these insects the best generic characters will be
found in the antennae, the shape of the head-parts, the vena-
tion and proportions of the wings : very slight changes in these
parts separating genera and species. Size and coloration,
which are usually very constant, afford good specific characters.

A good method of preserving larvae dry, adopted at Dresden,
is to squeeze out the intestines through a hole made near the
anal extremity of the larva, then to insert a fine straw, after
which it may be placed in a glass vase, itself placed in a tin
vessel and held over a lamp ; the larval skin is blown while
suspended over the lamp, by which the skin dries faster. It
may be done with a small tube or blow-pipe fixed at the end
of a bladder, held under the arm or between the knees, so as
to leave the hands at liberty ; and the straw which is inserted
into the body of the larva may be fastened by a cross-pin stuck
through the skin, and thus retained in its proper position
throughout the process of blowing. The small larvae, such as
those of the Tineae, may be put alive into a hot bottle, baked
until they swell to the proper extent and dry, when they can be
pinned with all their contents inside. (Westwood, Proceed-
ings of the Entomological Society of London, Sept. 7th, 1863.)

Dr. Knaggs has, in the Entomologist's Monthly Magazine,
given some directions for managing caterpillars. Very young
caterpillars, which will not eat the food provided, and become
restless, should be reared in air-tight jam-pots, the tops of which
are covered with green glass to darken the interior of the ves-
sel. When small larvae hide themselves by mining, entering
buds and spinning together leaves, they should have as small a
quantity of food as possible. In changing larvae from one plant
to a fresh one, a slight jar or puff of breath will dislodge them,
and they can be transferred to the jam-pot, or the glass cylin-
der, covered at one end with muslin, can be turned muslin end
downwards for them to crawl upon. The duplicate breeding
cage, pot or tube, should be "sweetened" by free currents of
fresh dry air and then stocked with fresh food.

Dr. Knaggs advises that "hiding places," or bits of chips,


etc., be provided for such Noctuid larva; as naturally lie con-
cealed, such us OrtJioHid; XdHthia, Noctua, etc., "while for
AI i rot is and a few others a considerable depth of fine earth or
sand is necessary."

"Larva?, which in nature hibernate, must either be stimulated
bv warmth and livsh food to feed up unnaturally fast, or else
through the winter must be exposed to out-door temperature."

Online LibraryA. S. (Alpheus Spring) PackardGuide to the study of insects, and a treatise on those injurious and beneficial to crops: for the use of colleges, farm-schools, and agriculturists → online text (page 22 of 29)