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THE

ELEMENTS

OF

INSECT ANATOMY

AN OUTLINE FOR THE USE OF STUDENTS IN THE ENTOMOLOGICAL

LABORATORIES OF CORNELL UNIVERSITY AND LELAND

STANFORD JUNIOR UNIVERSITY

BY

JOHN HENRY COMSTOCK

AND

VERNON L. KELLOGG

ithaca, new york

Comstock Publishing Co.

1895

QL THE

ELEMENTS

OF

INSECT ANATOMY

AN OUTLINE FOR THE USE OF STUDENTS IN THE ENTOMOLOGICAL

LABORATORIES OF CORNELL UNIVERSITY AND LELAND

STANFORD JUNIOR UNIVERSITY

BY •

JOHN HENRY COMSTOCK

AND

VERNON L. KELLOGG

ithaca, new york

Comstock Publishing Co.

'^95

Copyright 1895

by

John Henry Comstock.

«$p«M55fc

PREFACE.

The course of study outlined in the following pages is de-
signed to enable students to learn the more general features
of the structure of insects. It has been prepared especially
for students who devote only a short time to entomology ;
it may serve, however, as an introduction to a more ex-
tended study of the morphology of insects. Students mak-
ing a special study of entomology will be assigned more ad-
vanced work after they have completed this elementary
course.

While the more obvious object of this course is the learn-
ing of certain facts, a much more important thing to be
gained is a training in methods of careful observation. The
student is urged, therefore, to do the work with great care.

Chapters IV, V, and VI have been written by Professor
Kellogg ; the remainder of the work, by the senior author.

CONTENTS.

CHAPTER PAGE

I. Terms Denoting Position and Direction of Parts. . i

II. The External Anatomy of a Locust, Melanoplus femur-

rubrum 8

III. The Internal Anatomy of an Insect, Corydalis comuta 28

IV. The External Anatomy of a Beetle, Pterostichus cali-

fomicus 46

V. The External Anatomy of a Butterfly, Anosia

plexippus 57

VI. Specialized Mouth-parts of Insects 67

VII. The Venation of the Wings of Insects 7$

Index and Glossary 93

iv

CHAPTER I.

TERMS DENOTING POSITION AND DIRECTION OF PARTS.

Need of a technical nomenclature. — It has been found
that the use of the terms upper, lower, inner, outer, before,
behind, anterior, posterior, and similar expressions in the
technical descriptions of animals or their parts frequently
leads to ambiguity. A great part of the confusion doubtless
arises from the fact that the natural position of man differs
from that of the lower animals in being erect. Thus, for
example, when applied to man, before means in the direction
indicated by a line drawn from the center of the body to the
ventral surface ; in the lower animals it means in the direc-
tion indicated by a line drawn from the center of the body to
the head. The same difficulty attends the use of the term
anterior ; and of the opposite of these terms, behind and
posterior.

Another source of confusion in the use of this class of
terms is the fact that they are very commonly applied with
reference to the plane of the horizom. Thus above means
towards the zenith ; beloiv, towards the nadir ; and before
and behind indicate directions parallel to the plane of the
horizon. Consequently whenever the position of an object
is changed the terms denoting the relation of its parts must
be changed.

In order to avoid these difficulties a special set of terms
for designating the position and direction of the parts of
animals has been adopted by many writers ; and it is the
object of this chapter to define such of these terms as are
used in entomology.

Construction of the terms used. — Excepting the nouns
meson, dorsimeson, and ve?itrimeso?i , the terms used in this
work for denoting the position and direction of parts are
either adjectives or adverbs.

The adjectives end in al, as dorsal, ventral, and mesal.
The adjectives cephalic and intermediate are exceptions to
this rule.

The adverbs are formed by substituting for the adjective
ending the ending ad, the Latin equivalent of the English
suffix ward. Thus from the adjectives dorsal, ventral, and
mesal, are formed the adverbs dorsad, ventrad, and mesad.

In forming compound words indicating position or direc-
tion, the vowel o is substituted for the termination of the
first member of the compound, as dorso- ventral, caudo-
cephalic, and dextro-sinistral.

The six cardinal directions. — There are six principal
directions to which the position and direction of the parts of
a bilaterally symmetrical animal, like an insect, are com-
monly referred ; these are as follows : —

The cephalic directio?i or headward ; this is the direction
indicated by a line drawn from the center of the animal to
the head.

The caudal direction or tailward ; this is the opposite of
the cephalic direction.

The dextral direction or towards the right.

The sinistral direction or towards the left.

The ventral direction or bellyward ; this is the direction
indicated by a line drawn from the center of the body to the
ventral surface and forming a right angle with each of the
preceding directions.

The dorsal direction or backward ; this is the opposite of
the ventral direction.

The adverbial forms of the adjectives cephalic, caudal,
dextral, sinistral, ventral, and dorsal are cephalad, caudad,

dextrad, sinistrad, ventrad, and dorsad. Thus a part which
extends in a cephalic direction may be said to extend cepha-
lad.

Lateral and laterad — The terms dextral, dextrad,
sinistral, and sinistrad, are seldom used in the following
pages, as it is rarely necessary to specify one side as dis-
tinguished from the other. Instead of these terms lateral
and laterad are used.

Bxamplr. — The wings are lateral appendages of the body ; and in
most dragon-flies they extend laterad when the insect is at rest.

It is important here to define more definitely the direc-
tions indicated by these six sets of terms.

When we say that a certain part extends dextrad, we do
not mean necessarily that it extends towards the right side
of the animal or even towards a plane tangent to the right
side of the animal ; but that it extends towards a point which
is in a certain well understood direction* and which is at an
infinite distaiice in that direction. We are thus able to indi-
cate the position of an object which may be far exterior to
the body of the animal with whose position we are compar-
ing it. This is perfectly in accordance with the popular use
of the terms right and left.

According to this definition, all lines extending right and
left across the body of an animal are parallel.

The same may be said respecting ventro-dorsal lines.
Dorsad being eqdivalent to behind in the sense in which it is
applied to the body of man, or above as applied to the body
of a quadruped when in its natural attitude.

// is also true that all caudo-ccphalic lines are parallel.
This is a point to which careful attention must be paid, else
there is liability to error. It is quite natural to think that
cephalad means towards the head or towards the head end of
the body axis, and that caudad means toward the tail. The
fact is that cephalad means towards a point which is in a di-

* Indicated by a line drawn at right-angles to the cephalo-candal and dorsoven-
tral axes and towards the right side.

— 4 —

rection indicated by a line drawn from the center of the ani-
mal to the head, but at an infinite distance in that direction.
In other words, these terms must be used in a way analogous
to that in which we use right and left.

Examples.— Take a figure of a Dragon-fly with its wings extended
as when at rest. Draw a line from the distal extremity of one of the
wings to the head. Although this line extends directly towards the
head it does not extend cephalad ; but more or less nearly mesad.*
A line extending cephalad from the distal extremity of a wing (or
from any other part) is parallel to the cephalo- caudal axis of the
body.

Differences between the technical and popular uses
of cephalic and caudal. — It has just been shown that in
the use of these terms it is not the head and tail to which the
position and direction of parts are referred, but to two of
the cardinal directions which are at right angles to right and
left. Thus when an insect extends its antennae cephalad,
the most cephalic segments of these organs are those farthest
from the head. For the same reason we can speak of the
caudal part of the head or of the cephalic portion of the
tail. It will be seen that this does not accord with the
popular uses of these terms (as defined in the dictionaries)
according to which no part of the body is cephalic except
the head ; and of the different parts of the head one is just
as much cephalic as another.

Oblique lines. — The position or direction of a part
towards a point between two of the cardinal points, or
toward a point between one of the cardinal points and a line
connecting two other cardinal pojnts can be designated by a
compound term.

Examples. — A part which extends in a direction between those
directions which are indicated by dextrad and caudad is said to extend
dextro-caudad. A part which extends in a direction between those
directions which are indicated by dorsad and dextro-caudad is said to
extend dorso-dextro-caudad. This last direction would be indicated
in popular terms by saying : Towards the back and to the right and
towards the tail.

* Mesad is defined on a later page.

Meson, mesal, and mesad — Frequently the position or
direction of parts is referred to an imaginary plane dividing
the body into approximately equal right and left halves.
This middle plane is called the meson (fxearov, middle).
From meson are derived the adjective mesal and the adverb
mesad.

Dorsimeson and ventrimeson. — If it is necessary to
refer to the lines constituting the dorsal and ventral borders
of the meson, these are designated as the dorsimeson and
ventrimeson respectively.

Example. — The wing-covers of a beetle meet without overlapping
on the dorsimeson.

Ectal, ectad, ental, and entad. — It is often necessary,
especially in the study of internal anatomy, to compare parts
with relation to their nearness to or remoteness -from the
surface of the body. For this purpose the terms ectal (ckto's,
without) and ental (ivros, within) are used. The adverbial
forms of these terms are ectad and entad.

Examples. — The principal muscles of an insect are attached to
the ental surface of the body-wall, or to parts of the body- wall which
project entad.

Aspects of the body. — In describing animals it is often
desirable to specify that part of the body which looks in a
certain direction. For this purpose the term aspect is used
combined with an adjective indicating the direction in which
the surface in question looks.

Examples. — Dorsal aspect, ventral aspect.

Six aspects of the body are recognized ; these are the two
lateral (dextral and sinistral), dorsal, ventral, cephalic, and
caudal.* The fact that the outlines of the body of an animal
are more or less curved does not interfere with the practical
application of the above terms.

Proximal, distal, proximad, and distad. — In describing

* Cases occur where it is desirable to npeak of an aspect which looks in a direc-
tion between two of the cardinal directions. Thus we speak of the lines or spots
on the latero-dorsal aspect of a larva.

— 6 —

appendages of the body (legs, wings, etc.) the position of
parts may be referred to the two ends of the appendage by
use of the terms proximal and distal. Proximal indicates
nearness to the end of the appendage which is attached to
the body ; distal, to the end which is free. From these
adjectives the adverbs proximad (towards the proximal end)
and distad (towards the distal end) are formed.

Examples. — The proximal segment of the leg of an insect is the
coxa. The segments of the leg distad of the tibia constitute the
tarsus.

Aspects of appendages. — In addition to the two ends of
an appendage four aspects are recognized. To these the
same terms are applied as to the corresponding aspects of the
body: viz., dorsal, ventral, cephalic, and caudal. It is
therefore necessary to have a rule by which the correspond-
dence between the aspects of the body and of appendages
can be determined. In other words, a definite position must
be chosen as the normal position of an appendage. Naturalists
are quite well agreed as to what is the normal position of the
limbs of the Vertebrates. The following are what I believe
to be the analogous positions for the legs and wings of in-
sects.*

(a.) Wings. — Extended horizontally at right angles to
the body as are the wings of a dragon-fly (Libellula) when
at rest.

(£.) Legs. — Extended horizontally at right angles to the
body so that the convexity of the articulation between the
two principal segments of the leg (femur and tibia) shall
look dorsad ; and so that the surface of the tarsus ( ' ' foot ' ' )
which is usually applied to the ground when walking shall
look ventrad.

The dorsal, ventral, cephalic, or caudal aspect of a wing-

* The necessity for referring to the aspects of other appendages than the legs
and wings will so seldom arise that it does not seem worth while to attempt to
determiue the normal positions of such appendages.

or leg is that aspect which, when the wing or leg is in its
normal position, looks in the same direction as does the
aspect of the body which bears the same name.

First, second, third, etc. — When the individuals of a
a series of parts forming a portion or the whole of the bod}'
are indicated by the terms first, second, third, etc., the
cephalic member of the series is the first.

Example. — The first abdominal segment is the one nearest the
head.

When the series forms a part or the whole of an append-
age of the body, the first member of that series is the proxi-
mal one.

Example. — The first segment of a leg is the one which is articu-
lated to the body.

The direction of an appendage does not modify the above
rule.

Example. — The first segment of an antenna is the one which is
articulated with the head ; notwithstanding that when the antennae
are directed cephalad, as is usually the case, this segment is the one
nearest the caudal end of the body.

Intermediate. — In order to avoid ambiguity the word
mesal and its derivatives are used only with reference to the
meso7i. The second member of a series of three similar
parts is designated as the intermediate.

Limitations to accuracy. — As the body of an animal
presents but few plane surfaces or straight lines it is often
impossible to describe the position or direction of a part with
absolute accuracy. Practically, however, one will meet with
but few serious difficulties. Thus in describing the direction
of a curved or undulating line on the surface of the body it
will rarely be necessary to do more than to give the general
direction 'of that line ; the reader will understand that it
follows the sinuosities of the surface of the body.

CHAPTER II.

THE EXTERNAL ANATOMY OF A LOCUST.
(Mela?iophis femur-rubrum. )

Locusts or short-horned grasshoppers are excellent
subjects to use in beginning the study of the external an-
atomy of insects. They are very common and are compara-
tively large ; and the parts of the external skeleton in these
insects are, as a rule, remarkably distinct.

The species which has been selected as the basis of this
outline is the red-legged locust, Melanoplus femur-rubrum^
which is found in nearly all parts of the United States.
Specimens of this insect, preserved in alcohol, will be fur-
nished the student, who will be expected to verify carefully
or to correct each statement made in the text.

DIVISION OF THE BODY INTO REGIONS.

The body of a locust is composed of a series of more or
less ring-like segments. In the caudal part of the body the
ring-like nature of the segments is obvious ; in the cephalic
part it is less so. These segments are grouped into three
regions : head, thorax , and abdomen.

Head. — The head is the first or cephalic of the three
regions of the body. Apparently it consists of a single seg-
ment.

Thorax. — The thorax is the second or intermediate region
of the body. It is readily distinguished by its appendages ;
which are three pairs of legs and two pairs of wings. It
consists of three segments ; but as each segment is composed
of several distinct pieces, it requires considerable study to

— 9 —

trace the outlines of each segment. We will return to this
subject later.

Abdomen. — The abdomen is the third or caudal region
of the body. The segments of which it is composed are
more simple, distinct, and ring-like than those of the other
regions.

STRUCTURE OF THE BODY-WAU,.

Chitine. — In studying the anatomy of insects it is found
that in the adult state the greater portion of the body-wall,
that part of the insect which corresponds in position to the
skin of higher animals, is hard.

This hardness is due to the deposition of a horny sub-
stance, called chitine, in the membrane which constitutes the
body -wall.

Sclerites — The chitine is not evenly distributed through-
out this membrane. Pull the head of a locust so as to sepa-
rate it from the thorax as far as possible without breaking
the insect. Note that the head is joined to the thorax by a
soft flexible membrane, in which but little, if any, chitine
has been deposited.

Examine the sides of the thorax with a lens and observe
that the body-wall appears to be made up of man}' distinct
pieces. The integument is, however, really continuous ;
and in each case what appears as a distinct piece is simply a
portion of the body-wall in which considerable chitine has
been deposited. Such a portion of the body- wall is called a
sclerite*

Sutures. — The sclerites constitute the greater part of the
body- wall, the soft membranous portions separating them
being in most cases narrow. Usually these narrow portions
are mere lines ; they are then called sutures.

Frequently the sutures become entirely effaced. We are

* The sclerites are analogous to the centers of ossification in the bones of the
higher animals.

— io —

therefore often unable to distinguish certain sclerites in one
species of insect which we know to exist in another.
In such cases the effaced suture is said to be obsolete.

PARTS OF THE HEAD.

The principal portion of the chitinized parts of the head
are firmly joined together so as to constitute a box which
contains what may be called by analog}' the brain of the in-
sect and certain other important organs. To this are articu-
lated a number of movable appendages. The parts of the
head may be classed, therefore, under two divisions ; first,
the fixed parts ; second, the movable parts.

THE FIXED PARTS OF THE HEAD .

Compound eyes. — The most striking in appearance of
the fixed parts of the head are the eyes. These are two
large nearly hemispherical objects ; one on each side, form-
ing a considerable portion of the latero-dorsal part of the
head.

Study one of the eyes with a compound microscope, using
a low power. Note the honey-comb-like structure of the eye.
If you have difficulty in seeing this, remove a part of one eye
with fine-pointed scissors and mount it on a glass slip.
Each of the hexagonal divisions of the eye is a cornea
of a distinct eye. These large eyes are therefore compound,
and each of the small eyes of which they are composed is
termed an ocellus (plural ocelli}.

Make a drawing showing the honey-comb-like structure
of the cornea of a compound eye.

Note.— The drawings illustrating this course should be made with
great care, on good paper. Outline drawings are better than those
that are shaded, as shading tends to obscure lines indicating sutures.
The drawings should be made first with a pencil, then, after they
have been criticized, the lines should be inked.

Simple eyes. — Cephalad of the dorsal half of each com-

— II —

pound eye there is a small transparent hemispherical body.
These are the simple eyes. There is a third simple eye situ-
ated in a depression near the center of the cephalic aspect of
the head. The simple eyes are usually termed ocelli ; some-
times, stemmata (singular stem ma).

When the term ocelli is used in descriptive works, if there
is nothing in the context to indicate the contrary, it is al-
most invariably applied to the simple eyes, and not to the
elements of the compound eyes. In the same way the term
eyes usually refers to the compound eyes unless other-
wise indicated by the context.

Epicranium. — The simple eyes are situated in, and the
compound eyes surrounded by a large sclerite which consti-
tutes the greater portion of the fixed parts of the head or
cranial box. This sclerite is the epkranium. The cephalic
and lateral parts of the epicranium are separated on each
side by a suture which extends ventrad from the eye. The
ventral ends of these sutures are joined by a very prominent
suture which forms the cephalic boundary of the cephalic
portion of the epicranium.

Remove the head from the thorax and mount it on a
slender pin, inserting the pin in the center of the cephalic
aspect of the head. The pin will now serve as a handle.

Note the slightly elevated narrow ridge which separates
the lateral from the caudal aspect of the head. This ridge
marks the position of the suture which constitutes the caudal
border of the epicranium. Upon the dorsal aspect of the
head this suture is obsolete.

Upon each side joining the ventral end of the suture just
described and the ventral end of the one which extends ven-
trad from the compound eye is a well marked suture, which
forms the ventral border of the lateral part of the epicran-
ium.

(a.) Vertex. — The dorsal part of the epicranium is called
the vertex.

(b.) Front. — That part of the epicranium which is upon
the cephalic aspect of the head is termed the front.

(c.) Genes. — The lateral parts of the epicranium are
known as th.e gencr or cheeks.*

Clypeus. — Examine again the ventral border of that part
of the epicranium which is upon the cephalic aspect of the
head. Note that the prominent suture bounding this part
separates it from a very broad, but short sclerite. This is
the clypeus.

Although in a locust the clypeus appears like the basal
segment of an appendage of the head; from its form and
position in other insects it is classed with the fixed part of
the head.

Make a drawing of the cephalic aspect of the head'; and
name the fixed parts.

Occiput. — -Examine again the narrow ridge which sepa-
rates the lateral from the caudal aspect of the head, and
forms the caudal border of the epicranium. Note that it
may be easily traced on each side through the broad black
stripe which extends caudad from the eye ; and that dorsad
of that stripe it is obsolete. On each side of the head from
a point on this ridge a short distance ventrad of the black
stripe a suture extends across the caudal aspect of tlie head
to the membrane connecting the head with the thorax.
This suture constitutes the ventral border of the sclerite
which forms the caudal part of the dorsal portion of the
fixed parts of the head. This sclerite is the occiput. As
already indicated, the suture between the occiput and the
epicranium is well marked on the lateral aspects of the head ;
but on the dorsal aspect it is obsolete. Hence on this aspect
there is no indication of the line where the occiput ends and
the epicranium begins, f

*If the student finds it difficult to trace the sutures described here, he should boil
the head of the locust in a solution of caustic potash. This will destroy the soft
parts and bleach the walls of the head so that the sutures may be easily traced.

fThere is upon each gena a depressed line which appears like a suture but is not
one.

™ 13 —

Postgenae.-— On each side veutrad of the occiput and
caudad of the gena is a large sclerite. These form the chief
portion of the caudal aspect of the fixed parts of the head
and may be termed the postgcna.

The- postgenae and occiput form the boundary of the large
opening which connects the cavity of the head with that of
the thorax. The postgenae are separated from the epicra-
nium by the narrow ridge described above.

Tentorium — Carefully remove the appendages of the
ventral part of the caudal aspect of the head. This may be
done by lightly scraping with a knife. It will be seen that
the postgenae are connected by a strong part extending
from side to side, within the head. This is the tentorium.

Make a drawing of the caudal aspect of the head just pre-
pared ; and name the parts.

Gula. — When all the parts of the skeleton of the head are
present there exists a single sclerite which forms, typically,
the ventral part of the cranial box ; this is the gula. In
locusts the gula is not well developed, being represented by
merely a membrane to which the lower lip is attached.

Review. — -The fixed parts of the head of a locust consist
of five sclerites ; three of these, the occiput and the two post-
gence pertain to the caudal aspect, one, the epicranium , con-
stitutes the greater part of the dorsal, lateral, and cephalic
aspects, and one, the clypeus, forms the ventral portion of
the cephalic aspect. The epicranium consists of the vertex,
t\\e front and Vaegencz. The gula is not chitinized.

It should be observed that the head of a locust is bent
ventrad so that the mouth is not in the typical position for
the mouth of an insect, i. e., at the cephalic end of the head.
Imagine the head to be straightened so that the mouth is
at the cephalic end of the longitudinal axis of the body and
state upon what aspect of the head the clypeus is situated in
this case.

— 14 —

THE MOVABLE) PARTS OP THE HEAD.

Under this category are classed a pair of jointed append-
ages termed the antenna? and the organs known collectively
as the mouth-parts.

Antennae. — Just cephalad of each compound eye there is
attached to the head a long, thread-like, many-jointed ap-
pendage. These are the antenna?. Each antenna is situated
in a depression which is known as the antennary fossa.

Mouth-Parts.

Labrum — Articulated to the ventral border of the clypeus
is a broad, freely movable flap. This is the upper lip- or
labrum. .

Letter this part in the drawing of the cephalic aspect of
the head.

Mandibles. — Carefully remove the labrum. By doing
this there is exposed a pair of jaws which open by a meso-
lateral motion of each jaw. These are the mandibles. Each
mandible consists of a single short and thick piece, the distal
extremity of which is notched so as to form a series of teeth.

Remove the mandibles. This may be done by separating
them with a pin and turning each one laterad until it breaks
from the head.

Make a drawing of one mandible.

Maxillae. — By the removal of the mandibles there is ex-
posed a second pair of jaws which, like the mandibles, open
by a meso-lateral motion. These are the maxilla?. Unlike
the mandibles the maxillae are very complicated organs. We
will return to them later.

Labium. — Remove the head of the locust and pin it with
the caudal aspect uppermost to a piece of cork.

Note the freely movable flap which is the caudal part of
the mouth-parts. This and the crescent shaped piece to
which it is attached form the lower lip or labium.

— 15 —

The labium consists of the following parts : —

Submcnlum. — The submeutum is the proximal part of the
labium. It is nearly crescent-shaped, and is joined to the
membrane which connects the head with the thorax.
, NOTE. — It is believed by some writers tbat this crescent-shaped
part is composed of two fused sclerites, and that the caudal portion of
it represents the gula.

Mcntum. — This is the central portion of the labium ; and
is the principal part of that organ. It is articulated to the
distal margin of the submentum. To the distal margin of
the mentum are joined two movable flaps ; and to each
lateral margin is joined an organ consisting of three segments.

Labial Palpi. — These are the three-jointed organs of which
one is joined to each lateral margin of the mentum.

Palpiger. — The labial palpi are not joined directly to the
mentum. There is on each side of the mentum a sclerite
which bears the palpus of that side and which is called the
palpiger. The suture between the palpiger of each side and
the mentum is almost obsolete. Its position is indicated by
a slight groove which causes the palpiger to appear some-
what like a segment of the palpus.

Lignla. — This is the distal portion of the labium. It con-
sists of two large movable flaps.

Hypopharynx. — If the specimen has become dry so as to
be brittle, it should be softened with a little water.

With the specimen pinned as in last section, carefully lift
the ligula so as to expose the maxillae. Note the tongue-
like organ which arises from the labium and from between
the maxillae. This is the hypopharynx.

Remove the labium and place it on a glass slip in a drop of
Canada balsam or glycerine and cover it with a cover glass.
Examine it with a microscope using a low power. Make
a drawing of the caudal aspect of the labium, and letter the
parts.

Study the distal end of the distal segment of a labial palpus

— i6 —

with a higher objective. Observe the sense papillae with
which it is furnished. Make a drawing of this part.

Parts of the Maxillae. — After the removal of the labium
it is easy to distinguish the maxillae, of which there is one
on each side between the labium and the mandibles.

Remove a maxilla and mount it in Canada balsam or
glycerine, with the caudal aspect uppermost. Examine with
a microscope using a low objective.

Make a drawing of a maxilla, and name the parts, which
are as follows : —

Cardo. — The cardo or hinge is the proximal segment of
maxilla. It is triangular in outline in this insect.

Stipes. — The stipes or footstalk is the second .segment of
the maxilla ; it is the large, quadrangular sclerite which
forms the central part of the maxilla.

Lacinia. — Articulated to the distal end of the stipes is a
large sclerite', which tapers distad, is curved, and is termin-
ated by strong teeth ; this is the part known as the lacinia.

Galea. — Joined to the distal end of the stipes, laterad of
the lacinia, is a part consisting of two segments. This is the
galea. The distal segment of the galea is large, spoon-
shaped, and covers the inner lobe like a hood ; the proximal
segment is constricted in the middle so as to slightly resem-
ble a dumb-bell in outline. The galea is known as the outer
lobe, upper lobe, or superior lobe.

Palpifer. — Joined to the lateral border of the stipes and
between the cardo and the proximal segment of the galea is
a narrow sclerite ; this is the palpifer.

Maxillary Palpus. — Articulated to the distal end of the
palpifer is a long, slender organ consisting of five segments ;
this is the maxillary palpus.

After completing the drawing of the maxilla as a whole,
study the distal end of the distal segment of the maxillary
palpus with a higher objective, and make a drawing of this
part.

— i7 —

Review. — The mouth-parts consist of an upper-lip, la-
brum ; and under-lip, labium ; two pairs of jaws acting later-
ally between these lips ; and a tongue-like organ, hypo-
pharynx. The cephalic pair of jaws is called the mandibles ;
the caudal pair, the maxilla'.

Note. — The natural attitude of the head of a locust is such
that the labrum and labium appear to be fore and hind lips respec-
tively ; and the mandibles and maxilla, fore and hind pairs of jaws.
But when the mouth is in its typical position, at the cephalic end of
the body-axis, the labrum is an upper-lip, the labium an under-lip,
the mandibles, the upper jaws, and the maxillae the lower jaws.

Each maxilla consists of four primary and two secondary
parts. The primary parts are the eardo, slipes, lacinia, and
palpifer ; the secondary parts are the galea and maxillary
palpus.

The labium consists of the submentum, mentum, ligula,
two palpigers, and two labial palpi.

PARTS OF THE THORAX.

Division into segments. — The thorax consists of three
segments. The cephalic or first segment is named the pro-
thorax ; the second or intermediate, the mesolhorax ; and
the third or caudal, the mcta thorax.

These divisions of the thorax can be easily recognized by
the appendages they bear. To the prothorax is articulated
the first pair of legs ; to the mesothorax are joined ' the
second pair of legs and the first pair of wings ; and to the
metathorax, the third pair of legs and the second pair of
wings.

PROTHORAX.

Dorsal Part (Pronotum). — That which may be properly
termed the dorsal part of the prothorax is a large sunbonnet-
shaped piece which covers the greater portion of the sides as
well as the dorsal surface of this segment. This piece is
called the pronotum.

It is believed that the dorsal part of each thoracic segment
consists typically of four sclerites. These are named, be-
ginning with the cephalic, praescutum, scutum, scutellum,
and postscutellum. These sclerites may be distinguished in
the dorsal parts of the mesothorax and metathorax {ntesono-
tum and metanotum) of many insects ; but the pronotum
consists usually of a single piece. In the insect which we
are studying, although the pronotum consists of a single
piece, it is crossed by three well marked sutures, indicating
the division into four sclerites, which may be named as in-
dicated above.

On the latero-dorsal aspect of the pronotum the suture
between the praescutum and the scutum extends cephalad
for a short distance and is then interrupted ; the lateral por-
tions of this suture is parallel with and quite near to the
cephalic margin of the pronotum. Near the center of each
lateral aspect of the pronotum there is a short cephalo-caudo-
dorsal suture which separates the lateral fourth of the scutel-
lum from the mesal part of that sclerite. None of the
sutures extend to the lateral margin of the pronotum.

Make a drawing of the lateral aspect of the pronotum.

Ventral Part (Prosternum). — On the ventral surface of

this segment between the legs there is a sclerite which bears

a large tubercle ; this is the sternum of the prothorax or

i
prosternum.

Lateral Parts. — Owing to the great development of the
pronotum, which covers the larger portion of the sides as
well as the dorsal surface of the prothorax, the lateral parts
of this segment are rudimentary. The following named
sclerites, however, may be distinguished.

Episternum. — Between the pronotum and the end of the
lateral prolongation of the prosternum, which extends on
each side of the segment cephalad of the leg, is a conspicu-
ous triangular sclerite ; this is the episternum.

— i9 —

Jugular Sclerites. — In the membrane connecting the pro-
thorax with the head there is on each side, just cephalad of
the dorsal corner of the episternnm, a pair of sclerites.
These were named by a French entomologist pieces jugu-
1 aires* They ma}^ be called the jugular sclerites.

Note I. — The homology of these sclerites is not well understood.
They were supposed by Strans-Durckheim to represent the remains
of two distinct segments. But Newportf believed that they were
detached portions of the prothorax ; and suggested that they repre-
sent the paraptera of this segment.

Note II. — -It is believed that each lateral part of each thoracic seg-
ment consists of three sclerites. These are named the episternum,
the epimeron, and the parapteron. In many cases not all of these
parts can be distinguished. This may be due to the non-development
of a part, or to the effacing of a suture between two parts. In the
prothorax, paraptera have never been found unless, as suggested by
Newport, the jugular sclerites represent these parts. In many in-
sects the epimera of the prothorax cannot be distinguished from the
episterna, the suture on each side between these sclerites being ob-
solete. In the insect which we are studying, either this is the case
or the epimera of this segment are not developed.

Add the episternum and the jugular sclerites to the draw-
ing of the lateral aspect of the pronotum.

MESOTHORAX AND METATHORAX.

Union of these segments. — The second and third
thoracic segments are firmly joined together, forming a box
to which the two pairs of wings and the second and third
pairs of legs are joined. Owing to the intimate union of
these two segments it will be easier to describe them together
than separately.

With fine pointed scissors cut away the caudal border of
the pronotum, that part which overlaps the mesonotum ; be
careful not to break the membrane connecting the prothorax
and mesothorax.

*Straus-I)urckheim, Consideration G£nerales sur l'Antaoinie Coruparee des.Ani-
niaux Articules, p. 75.
f Article Insecta, Todd's Cycl. Anat. and Phys., p. 911.

20

Dorsal Part (Mesonotum and Metanotum). — The dor-
sal part of the mesothorax is termed the mesonotum, that of
the metathorax, the metanotum. Unlike the pronotum these
parts are confined to the dorsal aspect of the body. By cut-
ting away the caudal part of the pronotum as indicated above
and spreading the wings laterad, these parts are exposed.
Each consists of a nearly square area. To the lateral margins
of the mesonotum is articulated the first pair of wings ; and
to the lateral margins of the metanotum, the second pair of
wings.

The sutures indicating the outlines of the sclerites, of
which the mesonotum and metanotum are composed, are not
all well defined ; there is consequently some difficulty in
determining the limits of the sclerites.

In each of these segments only two of the four dorsal
sclerites are well developed ; these are the scutum and the
scutellum. The scutum occupies the cephalic half of the
segment, the scutellum the caudal half. The scutellum con-
sists of three parts : a central, shield-shaped part, which in
this species is closely united to the scutum ; and on each side
a part extending to the base of the wing. The caudal border
of the scutellum is thickened and is connected on each side
with the caudal border of the base of the wing by a cord-like
structure.

Make a drawing of the mesonotum and metanotum.
Note. — In those insects where the prsescutum and postscutellutn
are well developed, they usually extend entad and are often concealed
within the thorax. The connection of the scutellum on each side
with the caudal border of the base of the wing, is an -excellent guide
in tracing the homology of the parts of the mesonotum and the
metanotum.

Ventral Part (Mesosternum and Metasternum). —
On the ventral surface of the body between the legs of the
second thoracic segment is a large sclerite ; this is the ster-
num of the mesothorax or mesosternum. The cephalic

21

margin of the mesosternum is nearly straight ; the caudal
margin, deeply notched by a large, nearly square incision.

Caudad of the mesosternum there is a large sclerite, the
mesal part of which is prolonged cephalad so as to accurately
fit the notch in the caudal border of the mesosternum ; this
is the sternum of the metathorax or metasternum .

The caudal border of the metasternum is also notched, and
the first abdominal segment is dove-tailed into it.

Make a drawing of these parts.

Lateral Parts (Episterna, Epimera, and Paraptera).
— Examine one side of the second and third thoracic seg-
ments. Note that it is chiefly composed of four large
sclerites, which extend from the fossae of the legs dorso-
cephalad. These sclerites are named as follows : —

Episternum of the mesothorax. — The first or cephalic of
these four sclerites is the episternum of the mesothorax. The
sutures between the episterna and the mesosternum are only
faintly indicated in this species.

Epimeron of the mesothorax . — This is the second of this
series of sclerites.

Episternum of the metathorax. — This is the third of this
series of sclerites ;' it is the one which bears the oblique
yellow band characteristic of this species.

Epimeron of the metathorax . — This is the caudal member
of this series of sclerites.

Iu addition to the four large sclerites just described, ob-
serve the following named parts : —

Parapteron of the mesothorax. — Articulated to the dorsal
extremity of the episternum of the mesothorax and cephalad
of the base of the first wing is a small, inconspicuous, tri-
angular sclerite ; this is the pai'apteron of the mesothorax.

NOTE. — This sclerite can be seen more easily in the Carolina locust,
Dissosteira Carolina, a specimen of which will be shown the student
on request.

Parapteron of the metathorax . — Articulated to the dorsal

22

extremity of the episternum of the metathorax and eephalad
of the base of the second wing is also a small, inconspicuous
sclerite ; this is the parapteron of the metathorax. It is even
less well-developed than the parapteron of the mesothorax.

Spiracles and Peritremes. — Between the ventro-caudal
angle of the epimeron of the mesothorax and the fossa of the
leg is an organ which consists of a slit-like opening guarded
by two fleshy lips ; this is one of the openings of the re-
spiratory system ; these openings are called spiracles. When,
as in this case, a spiracle is surrounded by a circular sclerite,
such a sclerite is termed a peritreme.

In the membrane connecting the mesothorax with the
prothorax there is on each side a spiracle. This spiracle is
covered by the free margin of the pronotum. In this case
the peritreme is developed on the ventral side of the spiracle
into a prominent papilla.

Make a drawing of the lateral parts of the mesothorax and
metathorax.

Review. — The thorax consists of three segments, which
are named, beginning with the cephalic, prothorax, meso-
thorax, and metathorax .

The body wall of each of these segments is believed to consist
typically oieleven sclerites. Of these, /^rpertaintothe dorsal
part_pf the segment ; three, to each lateral part ; and one to the
ventral part.

The dorsal sclerites are named, beginning with the ceph-
alic, praescn turn, scutum, scutellum, and postscutcllum.

Of the two principal lateral sclerlites, the cephalo-veutral
one is the episternum, the caudo-dorsal one, the epimeron.
The third lateral sclerite is small, is* articulated to the epi-
sternum near the base of the wing, and is called the parap-
teron. Paraptefa .have not been found in the prothorax ;
but there has been found on each side, in the membrane con-
necting this segment with the head, a pair of sclerites termed
the jugular sclerites.

The ventral sclerite is known as the sternum. The sterna
of the three thoracic segments are designated as the pro-
sternum, mesostemum, and metastermim respectively.

The dorsal part of the body-wall of each segment is called
the tergum. This name is also applied to the dorsal part of
the three thoracic segments collectively.

The tergum of the prothoraxis frequently called the prono-
tum ; the tergum of the mesothorax, the mesonotum ; and
that of the metathorax, the metanoturn.

There are in this insect two pairs of thoracic spiracles.

APPENDAGES OF THE THORAX.

The appendages of the thorax are the legs and wings ; the
number and distribution of these have already been given.

Legs. — Examine the ventral aspect of the first pair of
legs. Each leg will be found to consist of the following
named parts : —

Coxa. — This is the proximal segment of the leg. It is
subglobular in outline. Examine the cephalic aspect of the
coxa, and note the longitudinal suture which traverses this
side of it ; this is shown better on the mesothoracic legs.

Trochanter. — This is the second segment of the leg, and
is much smaller than the coxa. The ventral aspect of it is
much longer than the dorsal.

Femur. — This is the third and principal segment of the
leg.

Tibia. — This is the fourth segment of the leg. It nearly
equals the femur in length, but is more slender.

Tarsus. — The tarsus includes all of that part of the leg
distad of the tibia. It consists in locusts of three segments.

The last segment of the tarsus bears a pair of claws.

On the ventral surface of the tarsus there is a series of
cushions ; these are called pulvilli. The distal segment of
the tarsus bears a single pul villus which projects between

— 24 —

the claws ; this is often referred to in descriptive works as
the pulvillus.

NOTE. — In the membrane connecting the coxa with the thorax, just
cephalad of the coxa, is a sclerite ; this I believe to be the trochantin.
The trochantin is a sclerite which is considered to be an appendage of
the coxa ; and its normal position is between the coxa and the epi-
sternum.

Make a drawing of one of the cephalic legs.

The same parts may be traced on each of the other legs.

Wings. — The wings are plate-like or membraneous ex-
pansions of the body-wall. Each wing is traversed by many
linear thickened portions ; these are termed veins, or nerves.
The principal veins extend proximo-distad. These are
joined together by many smaller veins or veinlets. The thin
parts circumscribed by the veins and veinlets are called cells.

The two pairs of wings of a locust differ remarkably in
form and texture.

Mesothoracic Wings ( Tegmina) . — The mesothoracic wings
are long, narrow, and of a parchment-like texture. They
are termed tegmina.

Metathoracic Wings. — The metathoracic wings are much
larger and of more delicate texture than the first pair of
wings. When not in use they are folded in plaits like a fan
and concealed by the tegmina. Some writers who designate
the mesothoracic wings as tegmina or wing-covers, describe
the metathoracic wings simply as the wings.

Make diagrams showing the outline of one of the wings of
each pair. Do not attempt to represent the veins and vein-
lets ; a special study of wing-venation will be made later in
the course.

parts of the; abdomen.

Number ot segments. — There is a difference of opinion
as to the number of segments in the body of a locust. The
difficulty arises from the complexity of the caudal end of

— 25 —

this region, and the fact that some authors have considered
the first abdominal sternum as a part of the metathorax.
Eight abdominal segments can be readily distinguished in
the female ; and nine, in the male.* Caudad of the eighth
abdominal segment of the female and the ninth of the male
are a number of sclerites which are considered by some
writers to be merely appendages of the abdomen ; other
writers hold that certain of these sclerites represent sterna,
and certain others, terga.

It is not within the scope of this work to enter into any
discussion of the matter. I shall describe the parts as if
there were eleven segments ; but wish the student to under-
stand that the so-called eleventh segment may be merely an
appendage of the tenth ; and that what is described here as
the ninth and tenth segments have not been considered as
such by certain very high authorities.

First Abdominal Segment. — The dorsal and ventral
parts of the first abdominal segment are widely separated by
the caudal part of the cavities for the insertion of the third
pair of legs.

The ventral part of this segment is dove-tailed into the
metasternum, and at first sight would be taken for a part of
the thorax.

On each side in the dorso-lateral part of this segment,
there is a large opening which is closed by a very delicate
membrane ; these are the auditory organs ; the membrane is
the tympanum .

Just cephalad of each auditory organ there is a small
opening ; these are the first pair of abdominal spiracles.

Second to Eighth Abdominal Segments — Each of the

*If a sufficiently large series of specimens of the red legged locusts be examined,
it will be seen that there are two kinds : one, in which the caudal part of the body
tape* s to the end, and bears four, pointed and curved, horny pieces ; and another, in
which the caudal part of the body increases in size caudad and is terminated by a
single, large, hood-shaped plate. The former is the female ; the latter, the male.

— 26 —

abdominal segments, from the second to the eighth inclu-
sive, is ring-like in form, and without appendages.

In each of these segments the lateral margins of the ter~
gum join the pleura* without any suture. Near the cepha-
lo-ventral angle of each pleurum there is a spiracle. The
sterna are well developed and are separated from the pleura
by a narrow, involuted, membraneous part.

Caudal Part of Abdomen of Female. — The most
prominent portion of the caudal part of the abdomen of the
female is the ovipositor. This is an organ consisting of four,
strong, curved, and pointed pieces, which form the most
caudal part of the body. With this organ the insect makes a
hole in the ground in which she lays her eggs. This is done
by alternately bringing together and separating the two pairs
of pieces, and at the same time pushing the body into the
ground. Examine carefully these pieces, and note how
well they are adapted to this purpose.

Between the ventral pieces is the opening of the oviduct.

Veutrad of this opening and also between the ventral
pieces of the ovipositor is a pointed prolongation of the
eighth abdominal sternum ; this has been termed the egg-
guide. Dorsad of the egg-guide there is a forked organ
which also is used in placing the eggs.

The ventral pieces of the ovipositor are supported by two
pairs of sclerites ; there being a sclerite closely applied to
the ventral surface of each pair, and one to the lateral sur-
face of each.

The ninth and tenth abdominal terga are shorter than any
of the preceding abdominal terga and are joined together on
each side, the lateral parts of the suture separating them
being obsolete.

*The lateral part of a segment is termed the pleurum ; in the same way that the
ventral part is called the sternum ; and the dorsal part, the let gum. By some
writers the entire dorsal part of an insect is called the tergum ; the lateral part,
the pleurum ; and the ventral part, the sternum. These writers apply the terms
tergile, pleurite, and sternite respectively to the dorsal, lateral, and sternal regions
of each segment.

— 27 —

Caudad of the tenth tergum there is on the dorsimeson a
shield-shaped piece ; this is believed to represent an eleventh
segment. It consists of two sclerites ; as is indicated by a
transverse suture.

On each side, projecting from beneath the caudal border
of the tenth tergum, is a pointed appendage ; these are the
cerci.

Entad of each cercus there is a much larger, triangular
sclerite which extends from the lateral border of the tenth
tergum to the caudal apex of the eleventh tergum ; these
are termed by Brooks* the podical plates ; by Packardf the
uropatagium.

By lifting the free end of the eleventh segment, the caudal
opening of the alimentary canal, the anus, is exposed ; it is
situated between the podical plates.

Caudad of the podical plate is the dorsal pair of pieces of
the ovipositor.

Make drawings of the dorsal and the lateral aspects of this
part of the body.

Caudal Part of the Abdomen of the Male. — In the
male ten abdominal sterna are present ; the tenth is a hood-
shaped sclerite on the caudal aspect of the body.

As in the female, the ninth and tenth abdominal terga are
united on their lateral margins.

Projecting from the caudal margin of the tenth tergum
there is on the dorsimeson a forked appendage, the furcula.

The eleventh tergum is furrowed by three deep longi-
tudinal grooves.

The cerci are situated as in the female, but are longer.

The podical plates are nearly as in the female.

Make drawings of the dorsal and the lateral aspects of this
part of the body.

*Handbook of Invertebrate Zoology, p. 253.
•(•Zoology, Advanced course, p. 309.

CHAPTER III.

THE INTERNAL ANATOMY OF AN INSECT.
( Corydalis corn nfa.)

The insect chosen for the study of internal anatomy in this
course is the larva of Corydalis cornuta. This larva lives
under stones in the beds of swiftly flowing streams ; it is
well known to sportsmen under the name of " dobson," and
is used extensively as bait for black bass.

As the larval state of Corydalis lasts nearly three years,
larvae which are at least two years old may be found at any
time. They are most abundant where the water flows
swiftest. A good way to obtain them is to hold a dip-net or
a wire screen in the stream below some stones, and, lifting
the stones with a hoe or garden rake, cause the current to
sweep into the net the insects which were under the stones.

This larva is probably the most desirable subject for an
elementary study of the internal anatomy of insects that can
be found in this country. The species is a large one, being
one of our largest insects ; there is a coarseness in its struc-
ture, which enables one to study the different viscera with
comparative ease ; if is furnished with well-developed organs
for aquatic respiration, and at the same time with equally
well-developed organs for aerial respiration ; and, as already
stated, fresh specimens can be easily obtained at any season,
even in mid-winter.

Unfortunately, however, the appearance of the insect is
very disagreeable to most people. But after a specimen has
been opened and pinned upon cork, as is necessary in the
study of the viscera, the disagreeable features are not vis-
ible ; and the ease with which the internal organs can be ex-

— 29 —

amined more than counterbalances the unpleasant part of
the preparation of the specimen.

PRESERVATION OF SPECIMENS.

Specimens that are to be used for the study of internal
anatomy should be preserved in an aqueous solution of chlo-
ral hydrate ; this is made by dissolving one part by weight
of chloral hydrate in twenty parts of water. This liquid
preserves the organs and at the same time leaves them flexi-
ble. After the specimens have been in the solution for one
day, a short, longitudinal slit must be made through the wall
of the abdomen, so as to allow the solution to enter the peri-
visceral cavity ; otherwise the viscera will decay. The de-
lay of one da}- before making the slit in the body is impor-
tant ; if the slit is made too soon, the muscles will contract
in such a way as to distort the specimen and render it worth-
less. One-half of the specimens should be slit on the dorsi-
meson, the others, on the ventrimeson ; for if the specimens
are all cut in the same manner, it will be impracticable to
study certain organs.

If a very careful study is to be made of the external anat-
omy of this larva, one or more spacimens should be left for
several days in a warm place, in the chloral hydrate solution,
without being cut. The parts bathed by the solution will
be well-preserved ; the viscera will decay ; and the gases of
decomposition will so distend the body that the different
sclerites will be spread apart.

EXTERNAL CHARACTERISTICS.

In order to understand the internal anatomy of this insect
it is necessary to know the more general features of its ex-
ternal anatomy. We will not stop to trace out the homol-
ogies of the different sclerites which enter into the compo-
sition of the body wall, but will merely examine the more
important external structures.

— 3o —

Pin a larva to the cork or beeswax lining of a dissecting
dish, with its ventral aspect uppermost, and cover it with
water. Make a drawing of the ventral surface. Name the
regions and the appendages of the body shown in this view.
The long, tapering appendages on the margins of the abdo-
men may be termed the lateral filaments ; the tufts of hair-
like appendages near the bases of the lateral filaments are
tracheal gills ; and caudad of the ninth abdominal segment
is a pair of prolegs. Thess may be termed, the anal pro-
legs*

Make a drawing of each of the following parts : —
i. The dorsal aspect of the head, showing the mandibles,
the antennae, and the labrum.

2. The ventral aspect of the head, showing the labium and
the maxillae.

3. The lateral aspect of the head, showing the number and
position of the eyes.

4. One of the true legs ; name the parts of the leg.

5. The anal prolegs.

6. One of the tufts of tracheal gills. First remove the
tuft with a pair of small scissors. Cut close to the ventral
surface of the body, so that the entire tuft will remain to-
gether. Examine the tuft with a lense or with a compound
microscope using a low power. The tuft is separated into
two parts by a deep fissure. The mesal part is the larger,
and is again divided into two parts. Each of these three
primary divisions is composed of several bundles of tracheal
gills. These are each composed of from two to twelve hair-
like branches.

7. One of the tracheal gills. Cut off several of the hair-
like branches and mount them in glycerine, using a thin

*Many larvae bear upon the abdomen locomotive appendages, which resemble
legs, and are termed prolegs. This is especially true of caterpillars, which bear
from one to five pairs of these appendages. The prolegs are temporary organs,
being shed with the skin when the larva transforms to a pupa.

cover-glass. Examine them with a compound microscope,
using a high power. The surface of each hair is marked
with numerous ridges, which resemble in appearance the
fine ridges on the skin of the palm of the human hand. In
the center of each hair, and extending nearly its en-
tire length, is a large tube. This is a trachea or air vessel.
Tracheae can be distinguished from other vessels by being
marked with transverse lines, which occur at regular and
very short intervals. The intimate structure of the tracheae
will be studied later ; but at this point the student should
become familiar with the appearance of tracheae, so that
when he dissects the insect he can readily distinguish them
from other vessels. Branching from this large central
trachea are numerous very small tracheae. Carefully trace
out the courses of the small tracheae and represent them in
your drawing.

8. A spiracle. State number of spiracles and the position
of each pair. Describe a spiracle. Do you observe any differ-
ences between the different spiracles of this insect ?

INTERNAL ANATOMY.

Preliminary work. — Take from the chloral hydrate solu-
tion a specimen which was slit on the ventral surface. Im-
merse the insect in water, with its dorsal surface downwards.
With fine scissors extend the slit on the ventrimeson the
whole length of the thorax and abdomen ; in making this
slit cut through the wall of the body into the perivisceral
cavity ; the body-wall consists of two parts, the external
crust of the insect, and, entad of this a wall of muscles ; it
requires considerable care to cut into the perivisceral cavity
and not injure the viscera. Make, on each side, in that
part of the body-wall connecting the prothorax with the
head, an incision extending from the longitudinal incision
to the side of the body.

— 32 —

' On the meson just entad of the ventral wall of the body,
there are two white cords, extending nearly the whole length
of the body. At intervals, which approximate the segments
in length, these cords are united ; at the points of union they
are greatly enlarged ; from these enlargements there arise
numerous, small, white cords, which extend in various direc-
tions. The two longitudinal cords, the enlargements upon
them, and the numerous cords branching from these enlarge-
ments constitute the nervous system ; the cords are nerves
and the enlargements are ganglia. The nervous system will
be studied later in a specimen which has been opened on the
dorsal side.

Cut away from the ganglia the nerves that extend to one
side ; do this with the scissors, first placing one blade under
the nerves and lifting them away from the other viscera.

Take a strip of sheet-cork a little longer than the insect
and twice as wide, and pin it to the beeswax lining of the
dissecting dish, and cover it deeply with water. Place the
specimen' on the cork and fasten with a pin at each end.
Turn laterad each half of the ventral wall and pin it down
to the cork, using ribbon-pins.

NOTE. — At the close of the day's work on this subject the student
should remove the strip of cork from the dissecting dish and place it
with the specimen still spread^ut upon it in a wide-mouthed bottle of
chloral hydrate solution. Bj^Poing this the work can be resumed
without the necessity of making a new dissection.

Ramifying through all parts of the body are numerous
trachea ; the larger tracheae are of a dusky color ; but many
of the smaller ones contain air, which renders them silvery
white. On -each side of the body, extending the entire
length of the thorax, are two very large tracheae ; from each
side of each abdominal segment except the last there arises
a large trachea, which divides and subdivides into numerous
branches. Cut a short piece from one of the large abdominal
tracheae, examine it with a compound microscope, and note

— 33 —

its characteristic appearance, so as to be able to distinguish
tracheae.

In the dissection of this specimen, the student may cut
tracheae and nerves freely ; but great care should be used
not to cut other vessels unless specially directed to do so.

In the center of the perivisceral cavity and extending the
whole length of the body, there is a large tube ; this is the
alimentary canal.

Adipose tissue. — Surrounding the caudal half of the ali-
mentary canal and attached to the lateral and dorsal walls of
the abdomen and thorax, there are large, flocculent masses
of a white substance ;' this is the adipose tissue or fat.

Make a drawing of a piece of adipose tissue showing the
general form of the masses.

Examine a bit of adipose tissue with a compound micro-
scope, using a high power, and make a drawing showing the
minute structure of the tissue ; in preparing the specimen
care must be taken to avoid crushing the fat cells by pressure
on the cover-glass.

In the farther dissection of this specimen the adipose tissue
may be cut away when necessary to see the parts studied.

Form of the Alimentary Canal. — Remove the ventral
wall of the head so as to exnose the alimentary canal
throughout its entire length. ^^F

Make a drawing of the alimentary canal and label the fol-
lowing parts : —

Pharynx. — The somewhat trumpet-shaped part of the ali-
mentary canal immediately caudad of the mouth is the. phar-
ynx.

(Esophagus. — That part of the alimentary canal which is
immediately caudad of the pharynx and which traverses the
caudal part of the head and the cephalic part of the thorax
is the oesophagus. It is a straight tube of nearly uniform
diameter except when some portion of it is distended by
food.

— 34 —

Proventriculus. — In the caudal part of the thorax the ali-
mentary canal begins to enlarge. This enlargement increase
gradually caudad until, in the first or second abdominal
segment, its diameter is' twice that of the oesophagus ;
then it contracts quite suddenly until its diameter is
less than that of the oesophagus ; this enlarged portion is
the proventriculus. It corresponds in function with the giz-
zard of birds and is very complicated in structure internally.

Ventriculiis . — Caudad of the constriction following the pro-
ventriculus, there is a slightly enlarged portion, from the
cephalic end of which, there project cephalad, four large
pouches ; this enlargement is the ventriculus or stomach and
the pouches are the gastric ca?ca. The two caeca of each
side are quite closely united.

Malpighian vessels. — Emptying into the caudal end of the
veutriculus are several, small, very long, and much convo-
luted tubes ; these are the Malpighian vessels ; they were
named in honor of Malpighi, one of the early anatomists.
As uric acid is found in the Malpighian vessels, they are sup-
posed to correspond to the kidneys in function.

Determine the number of Malpighian vessels.

Intestine. — The part of the alimentary canal extending
from the veutriculus totlie caudal end of the bod}* is the
intestine ; the part imrUPktely caudad of the veutriculus is
the small intestine ; following the small intestine is the large
intestine ; there are two bends in the cephalic part of the
large intestine ; the first extends dorsad and cephalad ; the
second, dorsad and caudad ; the rectum is not a well-defined
part of the intestine in this insect.

Attachments of the Alimentary Canal. — The alimen-
tary canal is attached to the body-wall and thus held in
place in various ways. The most obvious attachments are
those of the ends of this organ. In addition to these direct
connections, the alimentary canal is indirectly connected to
the body-wall as follows : —

— 35 —

By trachea. — From the lateral wall of each abdominal seg-
ment, large tracheae arise ; many of the minute branches of
some of these extend to the walls of the alimentary canal
and thus tend to hold it in place.

In connection with the tracheae, the action of the masses
of adipose tissue should be observed. These large masses,
which to a great extent are held in place by the tracheae
that extend to the alimentary canal, serve as cushions which
tend to keep the organ in place.

By muscles. — A large number of very delicate muscles ex-
tend from the ventral wall of the head to the oesophagus.
In the specimen which the student is now studying, only
the ends of these muscles which are attached to the oesopha-
gus can be observed, as the attachments of these muscles to
wall of the head were cut away in the preparation of the
specimen. L,arge muscles extend caudo-ventrad to the in-
testine from the line on the dorsal wall of the body between
the eighth and ninth abdominal segments. From within the
anal prolegs, muscles extend cephalad into the ninth abdom-
inal segment and are attached to the intestine. Other mus-
cles are described^ hi the next section.

By the suspensoria of the viscera. — There are several, long,
fine threads that are so attached as to tend to hold the ali-
mentary canal and other viscera in place. These may be
termed collectively the suspensoria of the viscera. In Cory-
dalis four pairs of suspensoria can be distinguished. These
are two pairs of suspensory muscles, a pair of ligaments, and
a pair of suspensory nerves.

The suspensory muscles arise from the body-wall in the
thorax, and extend caudad into the abdomen, where both
pairs are attached to the alimentary canal, and one pair to
other viscera also. It is rather difficult to trace out the
origins of these threads upon the body-wall ; but the threads
can be easily seen extending parallel with the oesophagus

— 36 —

and proventriculus, after they emerge from the layer of
muscles and fat.

Study first the suspeusoria of one side of the specimen,
leaving those of the other side for study when the final draw-
ing is made. In the following notes a single member of
each pair of suspensoria is described.

The two suspensory muscles may be designated as the
simple suspensory muscle and the branched suspensory
muscle, respectively.

The simple suspensory muscle arises from near the middle
of the ental surface of the pronotum, and extends caudad to
the gastric cseca, where the fibres of which it is composed
spread apart, some going to one caecum and some to the other.

Make a provisional sketch of this.

With fine-pointed scissors, cut off the tips of the two
gastric caeca of this side, and remove them with as long a
piece of the suspensory muscle as is practicable, and mount
them "in glycerine for study with a high power of the micro-
scope. Note the transversely striated appearance of the
fibres of this suspensorium. This indicates that it is com-
posed of striated muscular tissue.

Make a careful drawing showing the minute structure of
this suspensorium.

The branched suspensory muscle arises from the ental sur-
face of the body- wall, on the dorsal side, between the meso-
thoracic and metathoracic shields, near the lateral margin of
the body and extends caudad into the cavity of the abdomen ;
here it divides into several branches. One branch extends
to the ventriculus ; one or more to the masses of fat and to
the Malpighian vessels ; and one joins a suspensorium which
extends from a large trachea in the third abdominal segment
to the intestine.

Trace out the course of the branches of the branched suspen-
sory muscle, and make a provisional sketch showing their con-
nections.

— 37 —

The ligament of the viscera is not attached to the body-
wall, but is supported by a large trachea in the third abdomi-
nal segment, about which it forms a collar. This suspen-
sorium has three branches ; one of these extends caudad to
the testis or ovary ; one, cephalad, to the heart ; and the
third, to the intestine. This last branch receives the tendon
of one of the branches of the branched suspensory muscle.

Make a drawing representing the alimentary canal in the
center, a testis or ovary on each side (these are described in
the next section), and the three pairs of suspensoria. While
doing this the provisional sketches already made can be
utilized, but the observations should be confirmed by a study
of the suspensoria of the other side of the specimen.

Cut the trachea supporting the ligament of the viscera,
and slip the ligament off from it ; cut the ligament extending
to the heart as near to the heart as practicable ; cut the liga-
ment extending to the intestine, between the intestine and
the tendon of the branched suspensory muscle ; cut the
branched suspensory muscle as far cephalad as practicable ;
cut off the tip of the testis or ovary, leaving it attached to the
ligament ; mount the preparation thus made in glycerine for
study with the microscope, carefully spreading apart the
branches of the ligament and the end of the suspensory
muscle with a needle before putting on the cover-glass.
Study this preparation with a high power of the microscope
and note the difference in structure between the suspensory
muscle and the ligament of the viscera. Make a drawing
showing this.

The suspensory nerves of the alimentary canal extend from
the small intestine to the last abdominal ganglion. They
can be best seen in a specimen opened on the dorsimeson,
and will be described later.

The Reproductive Organs. — Although there appears to
be no external characteristic by which the sexes of the larva
of Corydalis can be distinguished, the internal reproductive

— 38 —

organs differ greatly in appearance ; the testes in this species
are long and narrow, while the ovaries are short and broad.
These organs are situated one on each side, between the
layer of adipose tissue which surrounds the alimentary canal
and the layer of the same tissue which is attached to the
sides of the wall of the abdomen. The testes extend from
near the middle of the third abdominal segment to near the
posterior border of the sixth abdominal segment. The
ovaries extend from near the middle of the fourth abdominal
segment to near the middle of the fifth abdominal segment.

Determine the sex of the specimen that 3^011 are studying
and do the work indicated below for that sex.

Reproductive Organs of the Male. — Note the shape of a
testis, .the connection of it with the respiratory system, the
groove in the middle of its mesal aspect, and the vessel in
the bottom of this groove. This vessel is the vas deferens
(plural, vasa deferentia) and is the outlet of the testis ; it
extends caudad to near the caudal end of the body. The
cephalic end of the testis is supported by the ligament of the
viscera already described.

Make drawings showing the external form of a testis.

Trace out the course of the vas deferens. This will require
very careful dissection, especially in the ninth abdominal seg-
ment, where the vas deferens passes under a muscle.

The triangular organ into which the two vasa deferentia
empty is the vesiculee scminalcs. If the specimen has been
opened on the ventral side, the visculae seminales will lie on
the alimentary canal, but if it has been opened on the dorsal
side it will be necessary to cut the intestine and turn back
the caudal part of it in order to see the visculae seminales.

The tube extending from the vesiculae seminales to the
external opening of the reproductive organs is the cjacn-
latory duct.

Make a drawing showing the relations of the testes, vasa
deferentia, vesiculae seminales, and ejaculatory duct.

_ 39 —

If the student has been trained in making histologic prepa-
rations, the structure of the testis may be studied at this
point.

Reproductive Organs of the Female. — Note the shape of an
ovary, the connection of it with the respiratory system, the
position of the oviduct (which is the vessel extending caudad
from the ovary), and the attachment of tn*e ligament of the
viscera.

Make drawings showing these things.

Each oviduct extends caudad from the caudal end of the
ovary through masses of fat to the seventh abdominal seg-
ment, where, at a point opposite the last ganglion of the
nervous system, it passes under the ventral muscles, and
terminates in a disc-like enlargement, on the body wall.

Make a dissection showing this.

Note. — In the adult the two oviducts extend caudad to near the
caudal end of the body where they empty into a short uterus.

Take one ovary and make longitudinal sections parallel
with the broader sides of the organ and make a drawing of
one of these sections, showing the ovarian tubes and the ova.

Take the other ovary and make longitudinal sections at
right angles to the broader sides of the organ and make a
drawing of one of these sections.

The Masticatory Organs of the Proventriculus. —
Remove the alimentary canal, and carefully open the proven-
triculus by a longitudinal slit. Cover a piece of cork with
white paper, spread out the opened proventriculus upon the
paper ental side uppermost, and fasten it in place with rib-
bon-pins. Fasten the cork bearing the preparation to the
beeswax in a dissecting dish, and cover the preparation with
water. Study it with a lens and with a compound micro-
scope, using a low power. Write a description of the masti-
catory organs, and make drawings illustrating them.

The Respiratory System. — Make a diagram showing

— 4Q

the arrangement of the larger tracheae, and write a descrip-
tion of the same.

The walls of the tracheae are
composed of three layers, which
correspond to the layers of the
^/L, body-wall ; in fact the tracheae
are believed to be invaginations
of the body-wall. The continu-
ity of the membranes of the
tracheae and body-wall is shown
diagrammatically in Figure i.
It should be observed that it is
the inner layer of the wall of the
trachea that corresponds with

Fig. i . — Section of trach ea and body-
wall, c cuticle; hy, hypodermis; the outer layer of the wall of the

dm, basal membrane ; sp. spiral
thickening of the intima. bodv

This inner layer of the wall of the trachea, the intirna,
like the cuticle is chitinous, and is shed from the tracheae
with the cuticle when the insect molts. This layer of the
trachea is furnished with thickenings, which extend spirally
and give to tracheae their characteristic, transversely striated
appearance. If a piece of one of the larger tracheae be
pulled apart the intima will tear between the folds of the
spiral thickening, and the latter will uncoil from within the
trachea like a thread. In some insects there are several,
parallel thickenings of the intima, so that, when an attempt
is made to uncoil the thread, a ribbon-like band is produced,
which is composed of several parallel threads.

Make preparations and drawings illustrating the structure
of the tracheae of Corydalis.

The Circulatory System. — Read the account of the
blood-vessels given in " Comstock'1 s Manual for the Study of
bisects. ' '

Make a drawing of the heart and the wings of the heart
of Corydalis. Note especially the number and arrangement

— 4i —

of the wings of the heart, and the structui^ of the cephalic
end of the aorta. Usually it is very difficult to determine
the number and arrangement of the chambers of the heart
in Corydalis ; this point may be omitted, therefore, in this
elementary course. Sometimes, however, some of the
valves can be easily seen. They occur near the middle of
each abdominal segment just opposite the point where the
cephalic edges of the larger wing-muscles join the heart.

Review. — Take a specimen that has been slit on the
dorsal surface and make a preparation similar to the one just
studied except that it is opened along the dorsimeson. Re-
view the work on internal anatomy indicated above except-
ing those parts referring to the nervous system, which will
be concealed by the alimentary canal in this specimen, and
to the circulatory system, which will be destroyed in the
preparation of the specimen.

Note especially the form of the reproductive organs, and
determine if the specimen is of the same sex as the one pre-
viously studied. If it is not, complete the work on the re-
productive organs indicated above ; if it is of the same sex
other specimens should be examined after the work on this
one is completed.

The Suspensory Nerves of the Alimentary Canal. —
Gently push the intestine to one side and note the two fine
threads extending caudad from the small intestine. Trace
out the connection of these threads or nerves with the
nervous system. Note the fine branches of these nerves
that extend to the caudal part of the intestine.

Make a diagram representing a side view of that part of
the alimentary canal caudad of the proventriculus, the last
three gangalia of the nervous system, and the nerves just
described.

The Peritoneum. — Cut the alimentary canal in two be-
tween the ventriculus and the first bend in the intestine.
Remove that part of the alimentary canal caudad of this

— 42 —

point. Cut the tracheae of one side extending to the remain-
ing part of the alimentary canal, so that it can be pushed
away to the other side. Be careful not to injure this part
of the alimentary canal till after the vagus nerve has been
studied, as indicated in a later paragraph. Take the speci-
men out of the water, and put a few drops of carmine solu-
tion on the muscles and nerves in the abdomen. Return
the specimen to the dissecting dish and try to observe the
peritoneum. This is a transparent, apparently structure-
less membrane, stretched over the floor of the abdominal
cavity in such a way as to protect the central part of the
nervous system. Owing to the transparency of this mem-
brane, it is very difficult to see it ; but when a specimen
is treated as indicated above, the fine particles of carmine
that become lodged beneath the peritoneum render it visi-
ble, especially when the carmine is washed off from the
muscles that are not covered by the membrane. The peri-
toneum is attached along each side of the body just lat-
erad of the great ventral muscles ; the points of attachment
are on the lines separating the segments of the body. Be-
tween the points of attachment, the margins of the mem-
brane curve mesad, giving the membrane the appearance of
being strongly stretched at the points of attachment.

The Nervous System. — After removing the alimentary
canal from the specimen opened along the dorsimeson, the
central nervous system will be exposed.

Make a diagram showing the disposition of the ganglia
and of the principal nerves of the thorax and abdomen.

Make careful dissections of the ganglia and nerves found
in the head, and make diagrams showing their arrangement.

The following parts should be observed and figured : —

The supraccsophageal ganglia. — These are two, large,
ovoid ganglia, lying above the oesophagus, and connected
by a short, thick commisure.

— 43 —

The antennal nerves. — These arise from the latero-cepha- *
lie angles of the supraoesophageal ganglia.

The optic nerves. — These arise caudad of the origins of
the antennal nerves. Determine the number of divisions of
each optic nerve.

The crura cerebri. — These are the two, large cords, one on
each side, connecting the supraoesophageal ganglia with the
subcesophageal ganglion, and forming with these ganglia
the nervous collar of the oesophagus. (The singular form
of crura is eras.)

The vagus nerve. — Just cephalad of the supraoesophageal
ganglia there is a minute ganglion, the frontal ganglion ;
this is connected by an arching nerve on each side with the
crura cerebri ; from the frontal ganglion there extends ceph-
alad a small, branching nerve ; from the frontal ganglion
there also extends a nerve which passes caudad, between
the supraoesophageal ganglia and the oesophagus, and ven-
trad of the aorta (which is usually turned to one side in
opening the specimen as this one is opened), to a minute
ganglion on the middle line of the oesophagus, caudad of
the supraoesophageal ganglia. From this minute ganglion
two nerves extend, one on each side, to the sides of the ali-
mentary canal, which they follow to the proventriculus,
where they divide into many branches. This system of
nerves and ganglia are termed the vagus nerve.

Tke stiboesophageal ganglion. — This is the large ganglion
on the meson, ventrad of oesophagus. From it two large
cords pass caudad to the first thoracic ganglia.

From the subcesophageal ganglia nerves extend to the
labium, the maxillae, the mandibles, and to other parts of
the head. The beginning students who are taking a short
course in entomology need not trace out these nerves.
Other students may use as a work of reference a paper on
this subject by Dr. William C. Krauss, published in
"Psyche," vol. IV, pp. 179-184.

— 44 —

The Muscular System. — In a fresh specimen the mus-
cles appear soft and translucent ; but in specimens that have
been kept for a considerable time in a preservative fluid, the}'
are firm and opaque. The greater number of the muscles
are attached to the ental surface of the body-wall, where they
form several layers. This is well shown in the abdomen,
where most of the muscles are for moving the segments of
the body. In the head and thorax, there are numerous
muscles for moving the appendages of the body, and their
arrangement is much more complicated.

To attempt to make a detailed stud}7 of the muscular sys-
tem would require much more time than can be devoted to
this system in this elementary course. Only the more gen-
eral features of the structure of the muscles and of their
arrangement will be noticed.

Note that the muscular system is composed of an immense
number of distinct, isolated, straight fibers, which are not en-
closed in tendinous sheaths as they are with vertebrates.

Mount a few of these fibers in glycerine, and study them
with a high power of the microscope. Note that the fibers
present numerous, traverse striations, like the striped mus-
cles of vertebrates.

Make a figure of a muscular fiber.

In this outline each series or layer of closely parallel
fibers. is considered as a separate muscle rather than an ag-
gregation of muscles. It complicates the subject unduly to
consider each distinct fiber a distinct muscle as has been done
by some writers. Thus lyonet in his "Traite Anatomiqiie
de la Chenille, que range le bois desaiile" describes 1647
muscles without including the muscles contained in the vis-
cera or those contained in the head.

Take a larva of Corydalis, which has been opened on the
ventrimeson and from which the alimentary canal and the
larger masses of fat have been removed, and study the en-
tal laver of muscles of the dorsal wall of the abdomen.

— 45 —

On each side of the heart and ectad of the wings of the
heart, there are great bands of longitudinal muscles, occupy-
ing the space between the heart and the prominent muscles
that extend dorso-ventrad on the sides of the body. Of the
longitudinal, dorsal muscles there are two sets on each side.
The wider set, which lie near the heart, may be termed the
great-dorsal-redi-muscles ; the narrower set, which lie be
tween the great-dorsal-recti -muscles and the dorso- ventral
muscles of the sides of the body, may be termed the small-
dorsal-recti-m uscles.

Of the dorso- ventral muscles of the sides of the body, re-
ferred to above, there are two large bundles on each side of
each segment ; they are situated near the union of the seg-
ments.

Between the lateral muscles and the cut edge of the speci-
men (the dorsimeson) lie the great-ventral-recti-muscles .
These differ from the great-dorsal-recti-muscles in' being
somewhat oblique (this is shown better in specimens opened
on the dorsimeson).

Make a drawing of the third, fourth, and fifth abdominal
segments respresenting the muscles mentioned above and
the heart and its wing-muscles.

Carefully remove the recti muscles in one or two abdomi-
nal segments and note that ectad of them are many muscles
extending obliquely in various directions. The study of
these oblique muscles will be omitted in this course.

Examine Plates VI, VII, VIII, XV, XVI, and XVII, of
the "Traite Anatomique de la Chenille" of Lyonet and
Plates III and IV of the "Considerations Gfneralcs sur
V Anatomie Comparee des Animaux Articulis" by Straus-
Durckheim.

CHAPTER IV.

THE EXTERNAL ANATOMY OF A BEETLE.
(Pterostichits calif ornicus. )

With the knowledge of the external anatomy of the
locust as a basis we may attempt to examine comparatively
some of the various conditions of the body exhibited among
different orders of insects. With the varied habits of in-
sects there are necessarily correlated various modifications
of structure, internal and external. The modifications of
the external structure are those taken special cognizance of
and used in the present analytical tables and keys for insect
classification, and must be studied to some degree before de-
termination of insect forms can be done intelligently. The
study of insect anatomy in a comparative way will also give
the student some understanding of the significance of
homology and specialization.

The peculiarly flattened form of many insects, by which
the lateral aspects of thorax and abdomen are reduced to a
mere ridge or margin, is accompanied by a change in the
position of many of the body sclerites, in particular the
pleural sclerites of the thorax. This condition is well ex-
emplified among the predaceous ground-beetles (Carabidae)
and almost any species may be selected for illustration. We
have chosen the species Pterostichus calif ornicus , as the
representative of a widely spread genus, and the description
following applies especially to this form ; however, the notes
will serve as a guide for the examination of any member of
the genus.

The meso- and metathoracic segments are closely joined

— 47 —

to each other and to the abdomen. The prothorax is freely
movable and is constricted at its articulation with the meso-
thorax, so that it appears to form all of the second or
thoracic region of the body. The insertion of the hinder
two pairs of legs, however, shows that part of what at first
glance appears to belong entirely to the abdominal region of
the body really belongs to the thorax. The body-wall is
very strongly chitinized, the body being enclosed in a verit-
able coat of armor. The hea'd projects horizontally from
the body instead of hanging vertically across the front, as
with the locust, and the flattening of the body is evident in
all regions, head, thorax, and abdomen. '

PARTS OF THK HEAD.
THE FIXED PARTS OF THE HEAD.

The fixed parts of the head are fused so as to form a
strong and rigid box, which is elongated and flattened.

Epicranium. — The epicranium bears on its cephalic por-
tion two impressed lines which run cephalad until they meet
the transversal clypcal suture, the suture separating the
clypeus from the epicranium. L,aterad of each of the im-
pressed lines on the epicranium there is, forming the dorso-
lateral margin of the head, a sharp ridge called the frontal
ridge, which runs cephalad from the dorsal margin of the
eye. The antennae arise just below the cephalic end of
this frontal ridge an a short, rounding groove running
cephalad from the eye. On the epicranium just above
each compound eye are two, long hairs arising from distinct
pits, these pits are called setigerous punctures. Similar punct-
ures and hairs' are found also near the lateral margins of the
clypeus.

Clypeus. — The clypeus is broader than long, and projects
cephalad between the bases of the mandibles. Projecting

cephalad from the cephalic margin of the clypeus, is the
subquadraugular labrum.

Compound eyes. — The compound eyes, on the lateral
margins of the head, are comparatively small.

Ocelli. — There are no ocelli.

Genae. — The portions of the epicranium ventrad of the
eyes and antennas are the gen cz and each projects cephalad,
latero- ventrad of the base of the mandibles, as a thin taper-
ing tongue curving slightly mesad at its tip. Ventrad of
this* projecting process, the gena presents a rounded
eniargination, and, filling in the emargination, may be seen
the basal portion of the maxillae. The genae form, with
portions of the occiput, the lateral portions of the ventral
surface of the head.

Occiput. — The occiput, although fused with the epicran-
ium to form the firm head-box , is plainly separated from the
epicranium on the dorsal and lateral portions of the head by
an impressed line, which fades out on the lateral portions of
the ventral surface of the head, so that the genal and
occipital regions cannot here be distinguished.

Gula. — Forming the mesal third of the ventral aspect of
the head, slightly widening caudad, and expanding at its
cephalic extremity to a narrow, transversal bar, which pro-
jects laterad to the genal "emargination, is the gula, one of
the head sclerites, which is wanting or is fused with the sub-
mentum in the head of the locust. The gula is usually a
well developed sclerite among beetles. The sutures separat-
ing it on either side from the contiguous portions of occiput
and epicranium (gena) are called the gular sutures.

Make a drawing of the ventral aspect of the head, show-
ing the skeletal parts described, and also what may be seen
of the mouth parts in situ.

— 49 —

THE MOVABLE PARTS OF THE HEAD.

Antennae. — The antenna are filiform, and n-segmented ;
the third segment is the longest one. The proximal , three
segments are glabrous, and the second and third bear each
two or three longish hairs near their distal end. The re-
maining eight segments are finely pubescent. In addition
each of these eight bears a few longer hairs at its distal end.

Mouth-Parts.

The mout/i-parts are fitted for biting and are in general
similar to the mouth-parts of the locust.

Labrum. — The labrum is conspicuous, with the distal mar-
gin slightly concave outwardly ; along this margin there are a
few, rather long hairs.

Mandibles. — The mandibles are rather long, and taper
distad to a sharp, curving tooth. They bear on their sharp,
cutting, inner margin, near the base, a few, small, blunt
teeth, and their outer face presents a broad, shallow groove
or furrow called the mandibular scrobe. Make a drawing of
a mandible.

Maxillae.— The maxilla differ especially from those of
the locust by the presence of an additional sclerite, the sub-
galea, by the side of the stipes, as if the stipes were divided
by a longitudinal suture. The cardo is large, and broadly
club-shaped ; the median portion of the maxilla is composed
of three sclerites, the stipes, palpiger and subgalea. These
three sclerites may be distinguished when the maxilla is
viewed from the ' dorsal aspect by the following characters :
the palpiger lies above the distal two-thirds of the stipes,
and also overlaps part of the subgalea. It is elongate, sub-
triangular in outline with apex directed toward the maxilla.
From it arises the four-segmented palpus, and it also bears
near the origin of the palpus a single, conspicuous, long

— 5o —

bristle. The stipes as seen from above is elongate and
rather slender, with the basal extremity widened. It lies
laterad of the large subgalea, which forms the inner or mesal
half of the portion of the maxilla. From the subgalea the
two lobes, galea and lacinia, of the maxilla arise. The
galea is slender, elongate, distinctly two-segmented, and pal-
piform in character. The lacinia is strongly chitinized, and
is strongly beset on its inner face with strong and long,
curved spines, and on its dorsal aspects with many, weaker
hairs. It bears on its distal end a strong tooth or curved tip,
known as the digitus.

Make a drawing of the dorsal aspect of a maxilla.

Labium. — The labium is separated from the cephalic
transverse portion of the gula by a straight, transverse
suture. The submentum is large, strongly chitinized, and
with its lateral portions appearing as broad, expanded lobes,
separated by a broad and deep, cephalic emargination.
Bordering this emargination is the narrow curving mentum,
with a mesal, cephalad-projecting, two-pointed tongue. From
the elongated, subcylindrical, cephalad-projecting palpigers
arise the three-segmented labial palpi, the first segments of
which are very .short. Also projecting cephalad from the
mentum is the ligula, composed of a dorsal or inner, deli-
cate, transparent, membraneous part, which divides distad
into two, slender, tapering projections, the paraglossia, and a
ventral or outer, chitinized, undivided portion, the glossa.
The tip of the glossa is truncate, and bears two, long, strong
hairs. The paraglossae lie slightly laterad of the distal half
of the glossa. The entire ligula arises, not from the cephalic
margin of the mentum, but from its inner or dorsal face, and
it may be that its parts are not homologous with the terminal
lobe (ligula) of the locust's labium, but that one or perhaps
both parts are continuous with the lining of the mouth
cavity ; in which case they would be homologous with the
hypopharynx of the locust's mouth.

— 5i —

Make a drawing of the ventral (outer) aspect of the
labium.

PARTS OP THE THORAX.

PROTHORAX.

Dorsal aspect. — The pronotum is not divided into differ-
ent sclerites, but appears as a single, firm convex plate, bear-
ing a median impressed line, and, laterad of this line, on
each side near the caudal margin, a short, linear depression.
At the acute lateral margins, the pronotum is inflexed, ex-
tending a little distance ventro-mesad on the ventral
(pleurals, sir.) aspeqt of the body. This inflexed portion
is often called the prothoracic epipleura.

Ventral aspect. — The sternum and the true pleural
sclerites or ' ' side pieces, ' ' together form the ventral aspect
of the prothorax.

Sternum. — The sternum, constituting the median region
of this aspect, is irregularly-saddle-shaped, with a caudad-
projecting tongue between the coxal cavities. This tongue
after reaching the caudal margins of the coxae bends at right
angles and projects dorsad, the end expanding slightly into
two, dorso-laterad projecting points, which meet a ventro-
mesad proj ectingpoint of the epimeron on each side, and thus
form part of the enclosing, caudal boundaries of the coxal,
cavities. *

Episternum. — The episternum, a large rhomboidal scler-
ite, constitutes most of the body wall between the sternum
and the epipleurae.

Epimeron. — Separated from the caudal extremity of the
episternum by a distinct suture, is the narrow, curving
epimeron, whose expanded mesal extremity presents two,
pointed, curving processes, which enclose the coxal cavity
laterad and caudad. The meeting of the epimeron and
sternum caudad of the coxal cavity technically closes it, or

— 52 —

makes it entire ; if these two sclerites do not meet, as is
often the case among beetles, and the cavity is bounded
caudad simply by membrane, the cavity is said to be open.
If there is no caudal tongue projecting between the cavities,
they are said to be confluent ; when separated, as in the
specimen in hand, by this tongue, they are technically
separate.

MESOTHORAX.

Dorsal aspect. — When the wing-covers are folded the
only part of the mesouotum visible is the small, median, tri-
angular or shield-shaped portion of the scutellum. By
spreading apart or breaking away the wing-covers, the lateral
membraneous portions of the scutellum may be seen, as well
as the scutum ; the median part of the scutum is strongly
chitinized and the lateral parts, weakly chitinized. The
postscutellum also may be distinguished as a narrow, weakly -
chitinized, curving bar, running laterad on each side just in
front of the caudal apex of the scutellum. The praescu turn
is represented merely by a thin, transversal strip of mem-
brane.

Ventral aspect. — As with the prothorax the ventral
aspect of this segment is composed of the sternum and the
pleural sclerites.

Mesosternum. — The mesostemum is plainly set off b}r
sutures. Its caudal margin has a broad, median tongue,
which projects caudad between the coxal cavities, and is
angularly emarginated at its tip. L,aterad of this tongue are
two, rounding emarginations, for the reception of the coxae.
Bounding each coxal cavity laterad is a caudad-projecting
portion of the sternum. Cephalad the sternal sclerite tapers
somewhat, and the cephalic margin is narrowly truncate.
A narrow, collar-like cephalic margin which fits into the pro-
thorax, is separated from the rest of the sternum by a slight
carina or elevated line.

— 53 —

Episternum. — The pleural sclerites are distinct ; the epis-
ternum is large, angularly concave, and does not reach the
coxa. It bears near its cephalic margin two, transversal,
raised lines or carinae, one of which is a continuation of the
collar-making carina of the sternum. Like the sternum, the
cephalic margin of the episternum fits into the prothorax.
The lateral margin is angularly inflexed along its entire
length, as is the case with all the pleural sclerites. The
narrow, inflexed portion is covered when the wing-covers are
closed by the inflexed, lateral margin of the wing-covers.

Epimeron. — The epimeron, lying along the caudal margin
of the episternum, is a narrow, transversal sclerite. Its mesal
extremity does not reach the coxal cavity, but lies contigu-
ous to the lateral margin of the metasternum.

Paraptera or Elytra. — The paraptera are remarkably de-
veloped into strongly chitinized, wing-like structures, called
the elytra or wing-covers. When the beetle is at rest, the
elytra fit closely over the dorsal aspect of the meso- and meta-
thorax and abdomen, protecting the abdomen and wings,
which (when present, as in most beetles) lie folded over the
metathorax and abdomen and beneath the wing-covers.
The elytra are articulated with the body so as to be freely
movable, being outspread when the beetle is in flight. The
basal or articulating parts of the elytra lie just ventro-laterad
of the lateral margins of the scutellum. The expanded flap
or wing-like parts present a series of sub-parallel, longitudi-
nal, impressed lines, and the lateral margins, termed epipleurce,
are inflexed over the dorso-lateral margins of the body.
This inflexed condition of the margins does not extend quite
to the tips of the elytra, but disappears at a point where the
margin appears to be interrupted. On the inner surface of
each elytron near the lateral margin there is a distinct longi-
tudinal fold or plica. The fore or mesothoracic wings are
wanting or are rudimentary in beetles, although the elytra

— 54 —

(paraptera) are popularly considered to be the modified*
fore wings.

METATHORAX.

Dorsal aspect. — When the elytra are closed the meta-
notum is completely covered and invisible. By removal of
the elytra, the metanotum is revealed as a narrow transversal
bar, on the surface of which a number of sutures and ele-
vated and depressed lines are to be seen. The work of dis-
tinguishing the various component sclerites of the metano-
tum cannot be done satisfactorily by the elementary student.
There is a conspicuous depression or groove extending cau-
do-cephalad along the dorsimeson, with strongly chitinized
margins, which project slightly mesad over the depression.
On the inner surface of the elytra, near the base of the mesal
margins, there are two, slight, projecting processes. These
small processes have strong, acute margins, which project
slightly laterad. When the elytra are closed, the raised pro-
cesses fit into the groove of the metanotum, and the laterad-
projecting margins of the processes lie under the mesad-pro-
jecting margins of the groove, the whole structure forming
a means for the firm holding of the elytra over the dorsum
of the body. The firm holding of the elytra is further aided
by the inflexed lateral margins and by the close dovetailing
of the mesal margins along the dorsimeson.

Ventral aspect. — As in the other thoracic segments this
includes both the sternum and the pleural sclerites.

Metasternum. — The metasternum is, as the mesosternum,
best described as saddle-shaped. It has a rather broad, blunt
tongue, projecting cephalad between the mesocoxseto meet the
caudad-projecting tongue of the mesosternum. It presents,
also, an acute-angled process, projecting caudad between the

*The homology of the elytra with the paraptera and not with the fore wings of
other insects was first pointed out by F. Meinert in 1880. In Dyliscus and in many
other beetles rudiments of the forewing exist beneath the elytra.

— 55 —

cephalic halves of the metacoxse. The "saddle-flaps," or
lateral lobes of the metasternum expand laterad, and their
cephalic margins, concavely rounded, form the caudal bound-
aries of the mesocoxal cavities. There is a line or suture
running transversely across the metasternum near the caudal
margin which does not reach the lateral margins. That
portion of the metasternum caudad of this suture is called
the antecoxal piece of the metasternum.

Epistermwi. — The rhomboidal epislernum is the largest
of the pleural sclerites.

Epimeron. — The trapezoidal epimeron, though smaller
than the episternum, is broader, and more conspicuous than
that of either of the other thoracic segments.

Paraptera. — The paraptera, lying on the dorsal aspect of
the body beneath the elytra, are small and weakly chitinized,
and may not be determined satisfactorily by the student.

Make a drawing of the ventral aspect of the entire thorax.

APPENDAGES OF THE THORAX.

Both fore and hind wings are wanting in this beetle. This
is exceptional, however, among beetles, the hind wings,
membraneous and with a few strong veins, being usually
well-developed, and differing from the wings of most insects
in being folded transversely as well as longitudinally when
the insect is at rest.

The legs are adapted for running, being long and slender.
The pro- and mesocoxse are globular, and the trochanters
distinct, but small. In the hind legs the coxse are large and
greatly expanded transversely, extending laterad as far as
the lateral margins of the metasternum. The coxee become
narrower laterad, tapering to an acute point. The trochant-
ers of the hind legs are very large and lobe-like. They pro-
ject along the basal half of the femur. The tarsi of all the
legs are distinctly 5 -segmented.

— ...6 —

PARTS OF THE ABDOMEN.

The abdomen is composed of a number of very much
flattened segments ; and its dorsal surface or tergum is com-
pletely covered by the elytra when the3^ are closed. On the
ventral surface, six strongly-chitinized sterna may be
counted. The first (basal) sternum is completely divided
by the coxal cavities, so that it appears as two triangular
pieces, lying laterad of the coxae. The cephalic margin of
the second sternum is emarginated on each side of the meson
by the coxal cavities, so that the mesal part of the cephalic
margin appears as an acute, cephalad-projecting process.
The third, fourth and fifth sterna are of about equal length
(caudo-cephalic), the sixth being longer and having its
caudal margin roundly pointed. The first, second and third
sterna are connate (firmly united, not movable on each other) ,
although the sutural lines are distinct. All of the sterna
have strongly chitinized, lateral margins, which project some-
what dorsad, and then are narrowly inflexed over the dorso-
lateral margin of the abdomen. There are seven terga, the
tergal aspect corresponding to the sixth sternum being un-
equally divided by a transversal suture, producing thus an
additional small tergum. All of the terga are membranous
except the sixth and seventh, which are chitinized, and are
known respectively as the propygidium and pygidhim. The
propygidium is coarsely punctulated, but the surface of the
pygidium is smooth. Each tergum except the seventh bears
a pair of spiracles, located near the cephalo-lateral angles of
the terga. Between the lip-like caudal margin of the pygi-
dium and the sixth sternum there is a transversal fissure, in
which lie the anal and genital openings.

CHAPTER V.

THE EXTERNAL ANATOMY OF A BUTTERFLY.

(Anosia plcxippus.*)

As a representative of the large order Eepidoptera, in-
eluding the moths and butterflies, the familiar "milkweed "
or •'monarch" butterfly, Anosia plexippus, has been se-
lected. It is commonly distributed all over the United
States.

PARTS OF THE HEAD.

THE FIXED PARTS OF THE HEAD. ■

In order to study the head of Anosia, it is necessary to
remove the scales which almost completely cover it. Rub-
bing with a soft, pointed brush, assisted by gentle manipula-
tion with a needle or delicate forceps, will soon denude the
head.* The antennae may be broken off if in the way. A
large part of the denuding may be done while the head is
still attached to the body of the specimen ; the denuding of
the caudal aspects must be done after removal. If the pro-
boscis is tightly coiled, as is probable, the head may be con-
veniently held by thrusting a dissecting needle through the
center of the coil.

Compound eyes. — The compound eyes are striking for
their large size, each one appearing to constitute about one-
third of the head. Examine a portion of the cornea under

* In addition to the denuded head used for examination it will be advisable for
the student to soften and bleach another head ; in the bleached or cleared head cer-
tain of the sutures can be more readily seen than in the merely denuded specimen.
The bleaching should be done as follows : A denuded head should be boiled for a
few minutes in dilute potassium hydrate until the ey s become light-brown; then
wash in water and transfer to eau de Labarraque, in which bleaching fluid the head
will soon reach the desired clearness.

— 58 —

high magnification. (Cut out a piece and mount in glycer-
ine, or dry, on a glass slide.) Notice the hexagonal shape
of the facets.

Simple eyes. — There are no simple eyes ; assure yourself
of their absence by examination.

Clypeus. — The cephalic aspect of the head is made up
chiefly of the rounding, tumid, shield-shaped clypeus. It
extends dorsad to the antennary fossae, and as a short, broad
tongue between them to a distinct suture extending trans-
versely from fossa to fossa. Ventrad the clypeus is bounded
by a subtransversely-running suture curving slightly dorsad
in its lateral portions. Ventrad of the mesal part of the suture
is the labrum ; and latero-ventrad of the lateral parts of the su-
ture are triangular expansions of the genes. The part of this
suture lying between the latero- ventral angles of the clypeus
and the triangular expansions of the genae is especially dis-
tinct, and in bleached specimens shows a noticeable expan-
sion at a point from which the suture running dorsad is
represented only by a raised line or sutural ridge. Laterad
the clypeus is separated from the gense (those narrow por-
tions of the genae which form the mesal orbits of the eyes)
by the sutural ridge just mentioned.

Epicranium. — The epicranium comprises a much smaller
proportion of the front of the. head than in the locust. It
composes most of the dorso-cephalic, dorsal, and dorso-
caudal aspects of the head. It is a suboblongate sclerite
with its "bounding sutures largely obsolete. A short, broad
tongue projects cephalad between the antennae meeting the
dorso-caudad-projecting tongue of the clypeus, but separated
from it by the short transversal suture. The epicranium
presents a tumid transverse space on the caudal aspect of
the head, ending in two, tumid, whitish spots.

Between the clypeus and the eyes are the narrow elon-
gated gencE. They compose the cephalic and part of the

— 59 ~

dorsal and ventral orbits of the eyes. Each gena presents a
triangular expanded portion lying between the base of the
maxillary proboscis and the caudo-mesal angle of the eye.

Postgenae. — The postgena; are two important sclerites,
constituting the caudal portions of the orbits of the eyes,
and also the lateral portions of the caudal aspect of the
head. The chief portion of the postgena are the broad sur-
faces caudad of the eye.

On account of the obliteration of certain sutures, a more
detailed study of the fixed * parts of the head is not feasible
for the elementary student.

THE MOVABLE PARTS.

Certain parts of the head plainly movable in the ^ocust
and in the beetle are immovable in Anosza, but their
homology with the movable parts heretofore studied, and
their homologous distinctness from the ' ' fixed parts ' ' of
the head, justify reference to these immovable but homol-
ogous equivalents of the movable parts of the head in other
insects as ' ' movable parts. ' '

Antennae. — The rather long, knobbed antenna', have
their insertions cephalo-mesad of the dorsal margins of the
compound eyes. Note the ringed or jointed structure of
the antennae, and the swelling club of the tip.

Labrum. — Immovably joined to the cephalo- ventral
margin of the clypeus is a very narrow, mostly transversal
sclerite, the labrum. It bears two, tapering, cephalad-pro-
jecting points, t\\e pih'fers, rising from the ends of the trans-
verse portion of the sclerite. Each pilifer bears on its mesal
margin a row of short, bristly hairs, light brown in color.
There is also to be made out a very small, triangular piece

* For a determinatian of the sclerites of the head of Anosia plexippus, based on a
comparative study of various lepidopterous heads, see article by the junior author
of these notes entitled "The Sclerites of the Head of Danais archippus Fab.'
[=Ansoia plexippus], in Kansas University Quarterly, Vol. II, No. 2, Oct., 1893.

— 6o —

projecting cephalad from the meson of the transverse portion
of the labrum. This is the epipharynx, a process rising
from the upper wall of the pharynx.

Mandibles. — The mandibles are wanting in Anosia.
(They are present in an aborted condition in many Lepi-
doptera ; and in one genus of small moths, Micropteryx, are
present and functional, constituting, with the maxillae which
are not produced into a sucking tube, true biting mouth-
parts. )

Maxillae. — The long, coiling, sucking tube of Anosia
(as of all the Lepidoptera possessing functional sucking
mouth parts) is composed of the greatly extended, opposed,
terminal portions of the maxilla;. In addition there is a
fixed basal part of each maxilla, which cannot be divided
into cardo and stipes. This basal part, shining brown, ex-
tends caudad and ventrad, partially bounding a cavity lying
between it and the labium. The sucking tube consists of
two lateral portions, each portion representing a maxilla.
These parts are convex laterad and concave mesad. By the
opposition of the two concave aspects, a complete central
tube is formed. The maxillary palpi are wanting in Anosia,
and in most of the butterflies, although present in a one- or
two- or even several-segmented condition among most of the
moths.

Labium. —The labium is a fixed, semi-membranous scler-
ite, triangular in outline, with its apex projecting cephalad
and joining the maxillar proboscis at its base. The labial
palpi are large, three-jointed, and covered with scales, and
normally project cephalo-dorsad. They are inserted on
tumid spaces on the base of the triangular labium, and the
first joint is pedicellate.

Make a drawing of the cephalic aspect of the head show-
ing the fixed and movable parts.

— 61 —

PARTS OF THE THORAX.

The three divisions or segments of the thorax vary much
in size and shape. It is interesting to note the coordinated
specialization of wings and corresponding thoracic segments.
The great development of the forewings in Anosia is attended
by a corresponding marked development of the mesothorax ;
and the reduction of the flight value of the hind wings is
paralleled by the reduction in size and importance of the
metathorax. The prothorax is altogether much reduced in
size and function. Its legs are small and weak.

PROTHORAX.

The prothorax is visible as a narrow ring or collar im-
mediately caudad of the head. On the dorsum may be
noted two prominent tumid portions, the " prothoracic lobes ' '
of Scudder, and caudad of these, and mesad, a small tri-
angular plate ; the tumid lobes constitute the scutum and
the triangular plate is the scutellum. Just caudad of the
scutellum are two lobes (smaller than the Scudderian lobes)
connected by a transverse piece. These lobes and trans-
versa bar are the postscutellum. The prczscutum is obsolete.
The pleura and sternum are united without visible sutures,
forming a "continuous ossified collar" encircling the pro-
thorax beneath.

MESOTHORAX.

The greatly developed mesothorax forms fully five-sixths
of the mass of the thorax. The prothorax is distinctly sep-
arate from the other thoracic segments, and is movable ;
but the meso- and metathoracic segments are much more in-
timately united.

Dorsal aspect. — The dorsum of the mesothorax quite
overshadows the metadorsum, and plainly shows two sclerites,
the scutum and scute/turn. (A third, the postscutellum, is
hidden beneath the metathoracic scutum. )

— 62 —

Scutum. — The scutum is much the larger of the two, con-
stituting, in fact, about two-thirds of the whole thoracic dor-
sum. It appears to be irregularly oblong in shape, sloping
dorso-caudad from its cephalic margin. Its latero-cephalic
angles are covered by broad flat leaves or plates, the patagia
(see below). A slight longitudinal mesal ridge, fading
away cephalad, is to be noted. A laterad projecting angu-
lated swelling occurs on each ventro-lateral border about
one-third of the caudo-cephalic length of the sclerite from
the ventro-caudal corner.

Scutcllum. — The scutcllum is a rather small, subquad-
rangular plate, just caudad of the scutum. A narrow pro-
cess projects cephalo-ventrad from each lateral angle of the
plate (the processes thus lying ventro-caudad of the ventro-
caudal angles of the scutum).

Lateral aspect. — The insertions of the forewings set off
the pleura from the dorsum. The three sclerites of each
pleura are easily made out ; and in addition, the large, divided
coxa and a portion of the sternum which runs latero-cephalo-
dorsad to meet the episternum give the appearance of three
additional pleural sclerites.

Episternum. — The episternum lies cephalad of the epimeron
and is roughly trapezoidal in outline.

Epimeron. — The epimeron is very oddly shaped, being
rather hour-glass-like in form with its long axis in an ap-
proximately caudo-cephalic direction. The broad portions
of the hour-glass are exaggerated by projecting, horn-like
processes. The cephalo-ventrad-projecting horn lies be-
tween the coxa and the episternum.

Parapteron. — The third pleural sclerite, the parapteron is
conspicuous because of its remarkable development into a
broad, flat lobe, overlying and protecting the costal inser-
tions of the forewing and to a considerable degree the dorso-
cephalic aspect of the mesothorax. This lobe is called the
patagium, by writers on the Lepidoptera.

-63-

Ventral aspect.— The sternum of the mesothorax is a
saddle-like, six-sided piece. Cephalad the bounding suture
runs transversely, but caudad the sternum projects by an
acute-angled process between the mesothoracic coxae. It
chiefly forms the pectus or chest of the insect. It bears a
median, impressed, longitudinal line.

METATHORAX.

The metathorax is much smaller than the mesothorax ;
its dorsum, especially so.

Dorsal aspect — The dorsum comprises but two sclerites :
the scutum and the scutellum. The scutum is divided into
two triangular pieces by the triangular, cephalad-projecting
scutellum. Neither the praescutum nor the postscutellum is
visible.

Lateral aspect. — The episternum is irregularly trape-
zodial, uniting with the sternum by a narrow dorso-ventral
neck or bar. Just cephalo-dorsad of its cephalo-dorsal corner,
lies the small hemispherical paraptcron. Caudad of the
dorsal half of the episternum lies the epimeron, a rather
large, irregularly-square sclerite, with a long, caudo-mesad-
projecting tongue running from its ventro-caudal corner.

Ventral aspect. — The metathoracic sternum is not easily
bounded. The suture between the episternum and the ster-
num is obsolete. The connecting bands running ventro-
mesad on either side from the episterna meet and expand on
the ventrimeson, forming a subquadrangular space.

Make a semidiagrammatic drawing showing the dorsal
aspect of the thorax.

Make a semidiagrammatic drawing showing the lateral
aspect of the meso- and metathoracic segments, including
the coxae of the legs.

-64-

APPENDAGES OP THE THORAX.

There are three pairs of legs and two pairs of wings in
Anosia. Note the small size of the first pair of legs. Make
out coxa, trochanter, femur, tibia, and tarsi in the legs.
Note the great development of themeso- andmetacoxae, and
note they are each divided longitudinally by a distinct suture.
They form a considerable part of the lateral aspect of the
meso- and metathoracic segments.

The forewings are larger and of more use in flight than
the hindwings, which is in contrast to the case with the
locust. The wings, like those of the locust, are membraneous
plates supported by a framework of strong, hollow veins
with strongly chitinized walls. The venation of the wings
affords important characters for classification, but we cannot
consider the subject here. Note that the upper and lower
surfaces of both fore and hindwings are covered with fine
scales. Rub off some of these scales upon a glass slide, and
examine with a high power. Note that each scale consists
of a little stem and a broad flat blade. This blade is longi-
tudinally striated. The scale is simply a flattened mem-
braneous sac, and the striae are fine ridges running along the
upper membrane. Examine a small bit of the wing from
which some of the scales have been rubbed off, note the
little pits or sockets in which the pedicel of the scales fits,
and note the regular arrangement of the scales into rows,
each row consisting of two tiers.

Make a drawing showing a part of the wing partly covered
by scales and partly denuded.

PARTS OF THE ABDOMEN.

The abdomen is composed of nine segments ; the first or
basal one is depressed, while the others are more or less
compressed. The second and third are the largest two seg-

— 65 -

merits in both male and female; the fourth, fifth, sixth, and
seventh are of nearly equal size and shape in the male ;
and the fourth, fifth, and sixth are similar in the female.
The tergum of the first segment is broad, flattened and
cushion-like, projecting slightly caudad over the second
tergum. The sternum of the first segment is unchitinized,
appearing as a narrow, membraneous space between the
metasternum and the well-chitinized sternum of the second
abdominal segment. This second sternum is traversed by a
transversal, elevated line or carina, which lies almost midway
between the cephalic and caudal margins of the sternum.
This carina does not, however, represent a suture. The
terga of the first seven segments in both sexes are separated
from the sterna by a pleural membraneous fold. In this
pleural membrane the spiracles, which occur only on the
first seven segments, are located. The terminal segments
differ in the sexes, and they must be considered separately.
In the * female the tergum of the seventh segment is
longer than the sternum, and bends somewhat ventrad,
forming, with the much reduced eight and ninth segments,
a sort of hood over a space partly enclosed by this hood,
partly by a bluntly pointed, caudad-projecting process of
the narrow sternum of the seventh segment, and partly by
the margins of this segment. This space is called the
vaginal vestibule ; in it lies the vaginal opening. The eight
segment is much reduced and compressed. Its sternum,
with the outer aspect facing cephalo- ventrad, forms the
roof of the vaginal vestibule, and is bordered by a thin,
distinct margin. The ninth segment is much more reduced
than the eight, and it usually lies retracted between and
almost concealed by the slightly projecting lateral margins
of the eight segment. It presents two, small, lateral lobes or
flaps, and a narrow sternal connecting piece.

* The sclerites of the caudal segments of the female can be much better studied
hi fresh specimens than in dry specimens.

— 66 —

In the male the seventh segment does not differ especially
from the sixth segment. The tergum of the eighth segment
is subtriangular, with curving sides, and the pleural mem-
brane is especially broad. The lateral portions of the ster-
num project caudad much beyond the caudal tip of the ter-
gum, as two, horny, double-pointed, thin, plate-like pro-
cesses, called the ''false claspers." These processes are not
articulated with the sternite, and are not movable as are the true
claspers of the ninth segment, but are projecting parts of the
sternum, and thus are not homologous with the body append-
ages. The tergal, lateral, and sternal walls of the ninth
segment are concealed within the eighth segment, but cer-
tain processes or appendages belonging to the ninth segment
are conspicuous. From the tergum a conspicuous, caudad-
projecting, tongue-like process arises, whose distal half is
divided longitudinally into two, lateral flaps or lobes, whose
tips are diagonally truncate. This dorsal process with
divided, distal portions is called the tegumen or sicula. Be-
tween the false claspers, there may be seen a pair of dark
pointed processes. These are the tips of the true claspers or
harpagones. Break away one of the false claspers, and the
true clasper of that side will be mostly exposed to view. It
consists of a subquadrate, plate-like part, with a median,
thickened and ridged portion lying on its mesal or inner
aspect ; projecting caudad from the. caudo- ventral angle of
the subquadrate part and continuous with the ridge of the
mesal face, there is a slender, but strong-pointed process, con-
cave outwardly, and bearing on its outer surface near the
tip a number of fine, transverse lines. Projecting caudad
from the dorso-caudal angle of the subquadrate part of the
true clasper there is a smaller and rather triangular process.

CHAPTER VI.

SPECIALIZED MOUTH-PARTS OF INSECTS.

The mouth-parts of the locust and beetle have already
been studied ; they represent, as a type, the generalized bit-
ing mouth-parts of insects ; (biting mouth-parts of general
identity with this type are found in the Neuroptera and in
the pseudo-neuropterous groups (the bird-lice, white-ants,
dragon flies, stone flies and others). The student has al-
ready become acquainted with the specialized, sucking
mouth-parts of the butterfly. Another type of sucking
mouth-parts, one in which all the parts of the mouth are
represented, is presented by the Hemiptera, for an easily ob-
tained and easily studied example of which we have chosen
the Dog-day Cicada, Cicada dorsata. As typical of the
piercing and sucking (or lapping) mouth-parts of the Dip-
tera we have described the mouth-parts of the horse-fly,
Tabanus sp., and of a house-fly, Musca domestica, speci-
mens of which are easily obtainable. Finally for that inter-
esting type of combined biting and sucking (or lapping)
mouth-parts presented by the Hymenoptera, we have se-
lected, as example, the common honey-bee, Apis mellifica.
The homologies of the variously appearing parts constitut-
ing these different types should be always held in mind.

THE MOUTH PARTS OP THE DOG-DAY CICADA.

( Cicada dorsata. )

The sucking beak, tapering from base to tip, arising from
the caudo- ventral part of the head, will be found in dried
specimens usually appressed to the ventral surface of the
body of the Cicada. The mouth-parts may be examined

and dissected in the dry specimen, or the head and mouth-
parts may be softened and bleached * before dissection.

Remove the head with the beak from the dried specimen,
and examine the beak before dissection. The long, three-
jointed labium, forming all of the beak as seen superficially,
is specially chitinized (brown) near its distal end. The
distal joint is the longest, and its surface is sparsely covered
with fine, whitish hairs. The tip is rather blunt than acute.
A narrow channel, widest at its proximal end runs along the
upper face of the labium. In this channel, but concealed
by the approaching edges of it, lie the mandibles and max-
illae. A glimpse of the mandibles and maxillae just at the
base of the labium can often be had. Above the base of
the labium is the minute, acute-angled labruin lying just
over the entering mandibles and maxillae.

With a dissecting needle carefully break away the head-
wall and muscle near the base of the beak, especially dorsad
and laterad. The bases of the mandibles and maxillce will
be discovered as small, strongly chitinized (brown), terminal
dilations of slender, chitin rods, which run forward into the
channel of the labium. Note the relative position of the
two rods with dilated bases on either side, and decide which
is mandible and which maxilla. (The rod lying slightly
dorsad and laterad of the other is the mandible ; the man-
dible is also thicker and larger than the maxilla. ) Trace
the slender chitin rods or stylets (the mandibles and max-
illae) into the channel of the labium. Here they are all
closely appressed, the two maxillae specially so, so that they
can be separated only with difficulty.

In the softened and clarified specimen, the mandibles and

* As in the bleaching of the locust and butterfly heads, the head with the beak of
the Cicada should be gently boiled in K O H until the parts are thoroughly soft and
clarified. If the clarifying proceeds too slowly, the head may be removed from the
K O H, washed in water, and placed in t,abbaraque's solution when the bleaching
will proceed rapidly.

-69-

maxillae are more easily separable. Removing them from
the labium note the channel in which they naturally lie.
The labium is more strongly chitinized along the walls of
the channel than elsewhere, except at its tip.

Make a drawing of the month-parts from dorsal view,
with mandibles and maxillae removed from channel of labium
and spread apart.

THE MOUTH PARTS OF THE HORSE-FLY.
( Tabanus sp.)

Select a female horse-fly (distinguished from the males by
the narrow space between the eyes ; in the males the eyes
touch for a greater or lesser distance along the dorsjmeson
of the head). The projecting mouth-parts are conspicuous.
On superficial examination there may be noted two, thick-
ened, slightly-curving, horn- or club-like processes (the
maxilliary palpi) projecting above a black, thickened stalk
or trunk (the labium), lying on the dorsal surface of which
a number of light-brown, slender, pointed stylets may be
seen.

For more detailed examination of the mouth-parts the
head of the fly should be removed from the body, a consid-
erable part of the head, laterad and caudad, broken away
and the remainder, with mouth-parts attached, boiled in
K O H to soften and bleach.

The large maxillary palpi are two-segmented; the distal
segment is longer than the basal one, and compressed. The
proximal one is subcyliudrical, and projects dorso-cephalad,
so that the large distal segment is carried above the rest of
the mouth-parts.

Lying along the dorsal surface of the large labial trunk
are six, long, slender, pointed pieces or stylets. The upper-
most, unpaired, flat piece is the labriun (or perhaps labrum

— 7o —

and epipharynx fused). It is rather bluntly tipped and -is
the broadest of the stylets. The fiat, smooth, sharply
pointed mandibles lie just above the less strongly chitinized,
narrower, and finely-marked maxillce. Corresponding some-
what to the labrum but less broad and strong, is the sixth
stylet, an unpaired slender piece lying below the maxillae.
This is the greatly developed hypopharynx* These six
stylets, labrum, mandibles, maxillae, and hypopharynx are
the instruments with which the female horse-fly pierces the
skin of animals to get at the blood ; the male has no pierc-
ing stylets, and feeds on flower-pollen.

Beneath the grouped stylets, is the long trunk- or proboscis-
like labium, presenting on its upper surface a shallow fur-
row in which the stylets may be partially enclosed, and
presenting at its distal extremity a conspicuous, expanded,
disk -like part called the labella. This terminal disk is be-
lieved to be composed of the greatly modified labial palpi.
It is made up of two, fleshy lobes or leaves, bearing on the
outer or under surface many, fane, transversal, subparallel
lines or ridges. The two lobes can be closed together like
the leaves of a book.

Make a drawing showing all' of the mouth-parts from the
dorsal view. The stylets can be spread apart laterad, so as
to expose the under ones.

In only a few families of Diptera are free mandibles pres-
ent, and when present they are possessed-^only by the fe-
males. In many flies there are no piercing stylets, and as
representative of these flies without piercing mouth-parts
the common house-fly may be studied.

*The hypopharynx is merely an outgrowth from the lower wall of the pharynx,
and is not, as are the other mouth-parts, a true appendage of the head homologous
with the body appendages (legs). The hypopharynx and epipharynx (outgrowth
from the upper wall of the pharynx) are in most insects small, fleshy, and incon-
spicuous.

— 7i —

MOUTH-PARTS OF THE HOUSE-FLY.

(Musca domestical

In the house-fly, we find only the maxillary palpi and the
proboscis-like labium, with well developed labella. The
maxillary palpi are prominent, but are only one-segmented.
The labial trunk or proboscis may be described as being
made up of three portions, a basal third, the basiproboscis,
from which arise the maxillary palpi, and in which are im-
bedded two slender chitinous rods, the " maxillary tendons,''''
probably representing the greatly reduced maxillae ; a mid-
dle third, the mediproboscis, strongly chitinized ; and a distal
third, the distiproboscis, including the disk-like, metamor-
phosed, fleshy, labial palpi, the labella. The labella is like
that of the horse-fly, but in the house-fly it is the only organ
for obtaining food. With it, traversed as it is by transverse,
horny, chitinous ridges, the " pseudotrachece " hard food
substances may be rasped so that fine particles of food mixed
with, or sometimes dissolved in, a salivary secretion, which
issues from the ridges, can flow into the mouth, along the
dorsal furrow oi the labial proboscis.

Make a drawing of the m*uth-parts from a lateral view ;
and also of a portion of the labella, highly magnified, to
show disposition of the pseudotrachese.

THE MOUTH-PARTS OF THE HONEY BEE.

{Apis mellifica.)

Most of the bees in alcohol, from among which the stu-
dent selects a specimen, will be found to have certain of the
mouth-parts protruding. These parts are the maxillae and
labium, united at base and associated to form a proboscis.
Before the detailed examination of these parts is begun, the
student should discover the labrum and mandibles.

— 72 —

Labrum. — The labrum is small and oblong in shape with
its latero-cephalic corners rounded. The breadth (dextro-
sinstral) is about three times its length (caudo-cephalic).

Mandibles. — Partially concealed beneath the labrum are
the spoon-shaped mandibles. With forceps or needle, press
the mandibles apart at their tips (press laterad). Note that
the mandibles are not toothed, but are rather paddle- or spoon-
like at the tips. Remove and make a drawing of a mandible.

Remove both mandibles and labrum, and grasp the re-
maining protruding parts with forceps and carefully pull
them loose from the head. Wash while still held in the
forceps, and mount in glycerine on a glass slide. Before
reading further the student should endeavor to name the
various parts presented before him on the slide. He should
refresh his memory as to the relations of the various sclerites
of the labium and maxillae, by reference to his drawings of
these parts in the insects already studied.

Make a drawing of the maxillae and labium, and name the
parts, tentatively. Compare the result with the notes fol-
lowing : —

Maxillae. — The parts of each maxilla present are the car-
do, stipes, galea (or lacina ; one of the two is probably
wanting), maxillary palpi, and possibly the palpifer.

Cardo. — The cardo, or proximal part of the maxilla is a-
rather long, slender, strongly-chitiuized sclerite, somewhat
resembling a human femur or thigh-bone in shape. At its
proximal end it terminates in two unequal prongs, the point
of the larger being bluntly rounded. At its distal end
(articulating with the stipes) it expands club-like.

Stipes. — The stipes is an irregular, elongate sclerite, strongly
chitinized. Its proximal end is bluntly rounded and swollen.
The stipes articulates with the proximal segment^of the galea
(see below) by a long diagonal face.

Galea. — The galea (we incline to believe this part homolo-

gous with the galea of the locust's maxilla, rather than with
the lacinia, because of its two-segmented condition), extends
distad from the stipes as a tapering blade-shaped piece. It is
composed of two segments. The proximal one is small
and triangular, articulating by the -entire length of one of
its margins with the stipes. The distal segment or sclerite
constitutes the real blade-like portion of the maxilla, and
nearly equals in length the ligula and labial palpi (see be-
low). Its surface is unequally divided into two portions by
a submedian, dark-brown, longitudinal line. (This line
may indicate a coalescence of galea and lacinia into this one
blade-like compound sclerite. ) This line bears several
hairs, and there are scattering hairs elsewhere on the scler-
ite, especially towards the distal end. Near the proximal
end of this distal segment of the maxilla, and between the
longitudinal line and the outer margin, many, two-jointed
papillae (taste organs? ) can be seen with a high power.

Maxillary palpi. — The maxillary palpi are minute, exar-
ticulate, outward-projecting pieces, arising from near the
outer end of the suture separating the proximal from the,
distal segment of the galea.

Labium. — The parts of the labium present are the sub-
mentum, mentum, glossa, paraglossse, palpifer, and palpi.

Submentum. — The submentum is a small, shield-like piece ;
its proximal end is connected by two chitinous bands, the
lora, with the cardo of each maxilla ; its distal end articulates
with the mentum. The submentum is rather feebly chit-
inized.

Mentum. — The mentum is rather oblong in shape with
rounding corners and strongly chitinized.

Glossa. — Rising from the distal end of the mentum is the
long glossa, which terminates in a small transparent lobe or
flabellum. The glossa should be carefully examined under
low and high magnification. Note the reticulated and hairy

— y4 —

surface. The visible surface is that of a sheath which en-
closes a slender, flexible rod, the rod being probably con-
cerned with the movements of the organ.

Paraglossce. — At each side of the glossa, and rising from
near its proximal end are two subtransparent lobes or flaps,
extending about one-fifth the length of the glossa. These
are the paj-aglosscs and are probably homologous with those
of the beetle's labium.

Palpifcrs. — Lying just laterad of the paraglossse, and
rising from the distal end of the mentum, are the palpifers,
extending forward for about one-half the length of the
ligula.

Labial palpi. — At the distal end of each ^palpifer is a
3-segmented labial palpus, the proximal joint being longer
than the other two combined. The palpifers and palpi bear
a few long hairs, especially on the distal ends.

Make a corrected drawing, if necessary, showing details
of labium and maxillae.

CHAPTER VII.

THE VENATION OF THE WINGS OF INSECTS.

In form an insect's wing is a large, membranous append-
age, which is thickened along certain lines. These thick-
ened lines are termed the veins or nerves of the wing ; and
their arrangement is described as the venation or neuration
of the wings.

It has been found that the venation of the wings of closely
allied insects is very similar, and that great differences in
this respect exist between insects remotely connected. Hence,
the wings afford excellent characters for use in the classifica-
tion of insects. In fact, as slight differences in venation are
easily observed, the wings being spread out like an open
page, these differences are probably the most available charac-
teristics of insects for taxonomic work. It is important,
therefore, that the student of entomology should learn earl}7
in his course the more important facts regarding this subject.

A careful study of the wings of many insects has shown
that the fundamental type of venation is the same in all of
the orders of winged insects. But this fact is evident only
when the more primitive or generalized members of different
orders are compared with each other. In most of the orders
of insects the greater number of species have become so
modified or specialized as regards the structure of their wings
that it is difficult at first to trace out the primitive type.

The specimens indicated for the student to study in the
following part of this course have been selected with care to
illustrate gradually increasing degrees of divergence from
the primitive type. In the case of each order studied the
work begins with a comparatively generalized form, and
passes step by step to those that are more specialized.

— 76-

Note. — The student should have a clear idea of the significance of
the terms generalized and specialized, which are now much used in
biology. Generalized indicates a primitive condition, a nearness to
ancestral forms. Thus the most generalized member of a group (as
a family or an order) is that member which most clearly resembles
the ancient progenitor of that group. Specialized, on the other hand,
indicates remoteness from the primitive t} pe, an adaptation to more
special conditions of existence. Thus the most specialized member
'of a group is the one that departs most widely from the ancient pro-
genitor of that group.

These terms are used in a comparative sense ; thus, a highly special-
ized form may be regarded as generalized when compared with forms
that are still more highly specialized.

A TYPICAL WING.

The flies of the genus Rhyphus afford good examples of
comparatively generalized wings. By studying the accom-
panying figure (Fig. 2) of one of these, the student can

Fig. 2. — Wing of Rhyphus.

gain a good idea of the type of the wings of insects belong-
ing to the order Dipt era, and have a standard with which to
compare wings of insects of other orders.

Longitudinal veins and cross-veins. — The veins can
be grouped under two heads : first, longitudinal veins, those
that normally extend proximo-distad ; and second, cross-
veins, those that normally extend more or less nearly
cephalo-caudad. In Figure 2, three of the cross- veins are

— 77 —

indicated by the letters c v ; two other cross- veins are repre-
sented near the base of the wing, but are not lettered. All
other veins represented in this figure are longitudinal veins.
The insertion of the word normally in the above defini-
tions is important ; for it is only in comparatively general-
ized wings that the direction of a vein can be depended
upon for determining to which of these two classes a vein
belongs. A little later the student will study wings in
which the direction of some of the longitudinal veins has
been so modified in the course of specialization that the
veins extend transversely (z. e. , cephalo-caudad), and some
cross- veins extend in a longitudinal direction (/. e. , proximo-
distad).

Simple veins and branched veins — Veins are either
simple or branched. The veins numbered II and IX in
Figure 2 are simple veins ; between these there are three
branched veins.

In the case of branched veins the entire vein including all
of its branches is often referred to as a single vein. Thus
the third vein in the wing of Rhyphtcs, counting the
thickened cephalic margin of the wing as the first vein, is
termed vein III ; and by this expression we include both
the main stem of the vein and its three divisions. On the
other hand, each division of a branched vein is often termed
a vein. Thus the first division of vein III, counting from
the cephalic margin of the wing, is termed vein Illr, and
the second division, vein III2, and so on till all are
numbered.

Note. — In the most generalized flies known to us vein III is five-
branched. But in most flies some of the branches of this vein
coalesce so that the number of apparent branches is less than five.
In JRhyphus, veins III2 and III3 coalesce so as to appear as a single
vein. In order to indicate that this apparently simple vein is com-
posed of two veins, and in order that homologous veins in different
insects shall bear the same number, this compound vein is numbered
vein III2 + 3. In the same way, what appears to be the third branch

-78-

of vein III in Rhyphus, is really the fourth and fifth coalesced, and is
numbered vein III4 + 5. The tracing out of the homologies of the
branches of veins, or veinlets as they are sometimes termed, is often
very difficult, but it is of the greatest importance in determining the
relationships of different genera or of families.

Names.of wing- veins. — There have been many differ-
ent sets of names applied to the veins of wings. Not only
have the students of each order of insects had a peculiar
nomenclature, but in many cases different writers on the
same order have used different sets of terms. This condi-
tion of affairs was incident to the beginning of the science,
the period before the correspondence of the veins in the dif-
ferent orders had been worked out. But now the time has
come when it seems practicable to apply a uniform nomen-
clature to the wing-veins of all orders ; and the following
set of terms has been proposed for that purpose : —

Costa. — The vein extending along the cephalic or costal
margin of the wing is the costa.

Subcosta. — Immediately caudad of the costa and extending
parallel with it, is a vein, which is simple in flies ; this is the
stibcosta (Fig. 2, II).

Radius. — Immediately caudad of the subcosta there is a
vein which in generalized insects is always branched ; this
is the radius. In Rhyphus, radius is three-branched (Fig. 2,
IIIi, III2+3, and III4+5).

Media. — Traversing the middle of the wing, there is a
longitudinal vein which is always branched in generalized
insects ; this is the media. In Rhyphus media is three-
branched (Fig. 2, Vi, V2, and V3, ).

Cubitus. — The third and last of the branched veins in flies
is the cubitus. This vein is two-branched in Rhyphus (Fig.
2, VII 1, and VH2)).

Anal furrow or first anal vein. — Immediately caudad of
the cubitus and closely parallel with it, there is in most flies
a prominent furrow in the wing ; this is the anal furrow or

79

the first anal vein. It is represented in Figure 2 by a dotted
line.

If this structure were always of the form that it bears in
flies it would not be termed a vein, but in many moths it is
thickened and appears like the true veins; it is, therefore,
termed a vein.

Note. — The anal furrow is of very great use in determining the
homologies of wing-veins. Except in very highly specialized insects
it is easily observed and makes a good starting point in working out
the structure of a difficult wing.

Anal veins. — The anal furrow divides the wing into two
areas, which may be termed the preanal area and the anal
area. The anal area, that part of the wing caudad of the
anal furrow, is usually transversed by one or more simple
veins ; these are termed the anal veins. The anal veins are
often designated as the first anal vein, the second anal vein,
etc. It should be remembered that in numbering the anal
veins the anal furrow is counted as the first anal vei?i.

Premedia and postmedia. —
In the May-flies there appears
to be a distinct, branched vein
between radius and media ;
this has been termed the pre-
media (Fig. 3, IV). There
also appears to be in May-flies
a distinct, branched vein be-
tween media and cubitus ;
this has been termed the post-
media (Fig. 3, VI).

Numbering of wing-
veins. — It is often more con-
venient to refer to the wing-
veins by numbers than by the

names that have been applied to them. The system of
numbering the veins that we have adopted is illustrated by

Fig. 3. — Wings of a May-fly, Hexagenia.

— 8o —

the numbering of the veins in Figure 2. By this system
the principal veins are numbered with Roman numerals,
and the branches of a vein are designated by Arabic sub-
numbers. Thus the branches of vein III are designated as
IIIi, III2, III3, III4, and III5, respectively.

The correspondence of the numbers and the names ap-
plied to the wing-veins by the writer is shown in the follow-
ing table : —

Costa = vein I.

Subcosta = vein II.

Radius = vein III.

Premedia = vein IV.

Media = vein V.

Postmedia = vein VI.

Cubitus = vein VII.

Anal furrow = vein VIII.

Other anal veins = veins IX, X, et at.

In most of the orders of insects there is obviously no
longitudinal vein between radius and media, and none be-
tween media and cubitus. In numbering the veins of the
wings of such insects, the numbers IV and VI, which have
been applied to the premedia and postmedia of May-flies,
are omitted. This is done in order that homologous veins
shall bear the same numbers in all orders of insects.

It is often necessary to refer to particular cross-veins ;
this can be done by using the numbers of the two veins
connected by the cross-vein ; thus a cross- vein extending
from vein I to vein II may be designated as vein I — II ;
and one extending from vein III to vein ,V, as vein III — V.
In reading these expressions the word to is substituted for
the dash, as " vein III to V."

When there is more than one cross-vein between two
longitudinal veins they may be numbered as follows : 1st
vein III — V, 2d vein III — V, etc. In lettering a figure the

— 8i —

word vein would be omitted and the legends would read
i st III— V, 2d III— V, etc.

NOTE. — The above statement will serve the needs of the beginning
student. But the advanced student will find in using the works of
certain writers that important modifications of this system of number-
ing the wing-veins have been proposed. For such students it seems
desirable to make the following statement, which may be omitted by
the beginner.

There have been several attempts to establish a uniform nomenclat-
ure for the wing-veins of insects. Of these that of Redtenbacher* is the
most important, being based on a much more extended study of the
subject than that made by any other author. He was the first author
to work out a system and apply it to all orders of insects.

The names and numbers of the wing-veins given above are those
adopted by Redtenbacher, except the names premedia, postmedia and
anal furrow, which were proposed by the writer. f These veins were
recognized and numbered, as above, by Redtenbacher, but not
named.

Redtenbacher, however, took the -^asgjs^^^^^BtSS?^

wing of a May-fly as the typical in- ---"'"" ~^^S^kw^^^^ ■'
sect's wing, and endeavored to find ^-jjS^^^?^.'',/

all the principal veins of this wing \ ^^^^^^^"'

in the wings of insects of each of the • \ vSv^*^

other orders. Later it was shown by ""-v. -'

SpulerJ and by the writer^ that in fig. 4.— Wing of Platephemera.

several orders of insects at least

there is no longitudinal vein between radius and media and
none between media and cubitus. The writer also pointed out the
fact that the veins premedia and postmedia were also wanting in the
wings of paleozoic insects, || and suggested that these veins had been
developed secondarily in the May-flies, as a result of the corrugation
of the wings of those insects.^ In support of this view, attention was
called to the fact that in the oldest May-fly known, Platephemera
antiqua of the Devonian age (Fig. 4), the cells of the wing are polyg-
onal in the areas traversed by these veins, while in the modern May-

* Josef Redtenbacher, Vergleichende studien iiber das Fliigelgeader der Insecten.
Ann. des k. k. natui historischen Ho/museums, IVein. Bd. I. s. 153-232, t. IX-XX.

t J. H. Comstock, Evolution and Taxonomy, The Wilder Quarter- Century Book,
pp. 37-114, PI. I-III.

J A. SruLER, Zur Phylogenie und Ontogenie des Fliigetgeaders der Schmetterlinge,
Zeiischrifl fur wissenschaftliche Zoologie. Bd. 1,111, s. 597-646, t. XXV, XXVI.

g J. H. Comstock, Evolution and Taxonomy. || /. c, pp. 66, 67.

f It may be, however, that these veins are detached branches of media.

— 82 —

Fig. 5.— Wings of a May-fly.

flies they are quadrangular (Fig. 5). This indicates that the longi-
tudinal, concave veins IV and VI were developed by a straightening

out of the zigzag lines between two
series of cells in each case. In tbe
wings of modern May -flies, not only
have longitudinal, concave veins
been formed from zigzag lines, but
the cross-veins extending between
these concave veins and the adjacent
convex veins have become strictly
transverse ; this is an arrangement
which iusures the preservation of
the corrugations.

Although it was shown that the
wing of a modern May-fly differs
essentially from the primitive type
of an insect's wing, and that the
veins premedia and postmedia are
absent in most of the orders of in-
sects it seemed desirable to base our nomenclature on the type con-
taining the maximum number of veins. The nomenclature of Red-
tenbacher was retained, therefore, with only such modifications as
were necessary. The most important of these modifications was the
omission of the numbers IV and VI in those cases where premedia
and postmedia are wanting.

Spuler, however, failed to recognize the veins premedia and post-
media at all. In fact there is no evidence in his paper that he has
studied the wings of May-flies. He therefore numbers the veins as
they occur in the Lepidoptera without omitting numbers for premedia
and postmedia.

In a recent paper* Dr. Packard has adopted the views of Spuler in
this respect. And I have come to feel that perhaps it would be
better for the sake of simplicity to refer to premedia and postmedia
by name only when speaking of the wings of May-flies, and to take
no account of them in numbering the wing-veins of other insects.

A similar course has been taken already in the case of the humeral
zreins of the Lasiocampidae.f In this family of moths, longitudinal
veins have been developed secondarily in the greatly expanded humeral
angle of the hind wings (Fig. 6, h.v. ). These veins are referred to
merely by name, no account being taken of them in numbering the
principal veins.

*A. S. Packard, On a Rational Nomenclature of the Veins of Insects, especially
those of Lepidoptera, Psyche, May, 1895.
^Evolution and Taxonomy, p. 89.

VIIi

— 83 —

I regret that this conclusion was not reached before the figures and
descriptions of wings in " Corns lock's Manual for the Study of I11-
sects " were prepared. Should
a second edition of this work
be needed, it is quite probable
that a revised system of num-
bering the wing-veins will be
adopted in it. The beginning
student, however, is advised
to use in this course the sys-
tem given on page 80, in order
to avoid confusion when using
the " Manual. " It should be
remembered that, although it
is exceedingly desirable that
all entomologists should use
the same system of number-
ing the wing-veins, the adop-
tion of any particular system
is of much less importance
than a clear knowledge of the
homologies of the wing-veins.

The following table shows
what seems to the writer to be
the most simple and hence the
most desirable system of numbering

Costa = vein I.

Subcosta — vein II.

Radius = vein III.

Media = vein IV.

Cubitus = vein V.

Anal furrow = vein VI.

Other anal veins = veins VII, VIII, et al.

The above system agrees with that proposed by Spuler and adopted
by Packard, in not numbering premedia and postmedia. But it differs
in a very important particular from the S3'Stem of these writers. They
do not number costa, but begin with subcosta, which they term vein I.

In defense of this, Dr. Packard says :* " Spuler shares the opinion
of Fritz Miiller (Termitidae), Brauer and Redtenbacher (Libellulidae),
and Haase (Papilionidas), that costa is only a hypodermal structure, a
thickening of the edge, which does not have a trachea as its origin
(anlage), and which, therefore, has nothing to do with the veins."

It may be that the costa does not originate in the same way as other

Fig. 6. — Wings of Clisiocampa.
the wing-veins : —

*/. c, p. 236.

veins,* but, if we except the Lepidoptera, it is usually present and in-
distinguishable in structure from the other principal veins ; and ex-
cept by writers on the Lepidoptera, it has been generally recognized
and named as one of the principal veins of the wing. It seems de-
sirable, therefore, to include it in numbering the wing-veins.

In fact, there are much stronger reasons for counting costa a vein
than there is for including the anal furrow in the list of veins, as is
done by these very writers who exclude costa. The anal furrow arose
iu an entirely different way than did the wing-veins,f and except in
the Lepidoptera it almost never resembles a vein in structure. But,
as the anal furrow becomes a well-developed vein in the Lepidoptera,
and is present, though in a different form, in nearly all winged insects,
it simplifies the nomenclature to include it in the list of veins.

There is one other point which the student should clearly under-
stand in order to avoid confusion when he comes to use the special
works treating of the Lepidoptera. Although costa is present in the
wings of many of the more generalized moths, it is wanting, as a rule,
in the Lepidoptera. This fact being overlooked by the writers on this
order, they have applied the term costa to the vein that is called sub-
costa in other orders of insects, and have applied the term subcosta to
the vein that bears the name radius in other orders. It is to be hoped
that writers on the Lepidoptera will soon conform to the usage of
writers on all other orders of insects. The change need necessitate
little if any confusion, as the use of the term radius will indicate
that the writer using it has adopted the uniform nomenclature for all
orders.

Convex veins and concave veins. — In most insects,
except L-epidoptera, the wings are more or less corrugated.
This is very well shown in the wings of dragon-flies, one of
which should be examined at this point in the course. Note
that as a result of this corrugation some of the wing-veins
extend along the summits of ridges ; such wing-veins
are termed convex veins. Other wing- veins of a corrugated
wing extend along the bottoms of furrows ; such veins are
termed concave veins.

Note that a corrugated wing is much stiffer than it would
be otherwise.

Numbering of the cells of the wings. — In numbering

*See Evolution and Taxonomy, p. 59.
t Evolution and Taxonomy, p. 60.

— 85 —

the cells of the wings, according to the system proposed by
the writer,* each cell is designated by the name or number
of the longitudinal vein that normally forms its front
(cephalic) margin. This is illustrated by Figure 7, in which

tiTi m,
n ! mi \

Fig. 7.— Wing of a butterfly.

the numbers placed opposite the ends of the veins refer to
the veins ; the others, to the cells.

When a cell is divided by cross-veins into two or more
parts, the parts are numbered, beginning with the proximal
one. Thus in the wing of Leptis (Fig. 8) cell I is divided

vn>+ix

Fig. 8.— Wing of Leptis.

by a cross- vein. In this case the first part (not numbered
in the figure) is 1st cell I ; and the second part is 2d cell I

* Evolution and Taxonomy, p. 93.

— 86 —

(lettered 2d I). In this wing also cell III is divided into 1st
III and 2d III ; and cell V2, into 1st V2, and 2d V2.

Margins of wings. — An insect's wing is more or less
triangular in outline ; it, therefore, presents three margins;
the costal margin (Fig. 7, a-b) ; the outer margin (Fig. 7,
b-c), and the inner -margin (Fig. y, c-d).

Angles of wings. — The angle at the base of the costal
margin (Fig. 7, a) is the humeral a?igle ; that between the
costal margin and the outer margin (Fig. 7, b) is the apex
of the wing ; and the angle between the outer margin and
the inner margin (Fig. 7, c) is the anal angle.

THE WING- VEINS OF DIPTERA.

As the chief object of the following work is to give the
student training in tracing the homologies of wing- veins,
comparatively little information will be given directly. The
student will be furnished in each case with the wing
to be studied, and his studies should take the following
course : —

Directions for the study of wings. — Make a drawing of
the wing, based upon a careful study of it with a compound
microscope, using a low power. The drawing should be
first made with a pencil ; after it has been criticised by the
teacher, the lines should be inked. Make the drawing 011 a
sufficiently large scale so that each vein can be represented
distinctly ; in most cases the drawings should be somewhat
larger than Figures 7 and 8.

Number each vein and cell of the wing.

Write a description of the wing, noting the more important
features of its venation, and especially the more important
departures from the primitive type of the order as indicated
by the generalized form first studied. In the Diptera the
wing of Rhyphus (Fig. 2) may be used as a generalized
type, although in certain respects other wings will be found
to be more generalized.

— 87-

The following are some of the more important points to be
noted in the descriptions : The extent of vein I. The ex-
tent of vein II. The number of branches of vein III ; in
this connection determine which of the radical cells has been
obliterated by the coalescence of branches of vein III. The
position of the cross-vein III-V ; the number of branches of
vein V ; the division or not of cell V2 ; the presence or ab-
sence of cell V3 ; the courses of the branches of vein VII2 ;
and the course of vein IX.

Wing of Protoplasa. — Study the figure of the wing of
Protoplasa fitchii (Fig. 9) as an illustration of a wing in
which radius is five-branched. Do not be confused by the
spur at the base of vein III2+5 (marked ^ in the figure) ;
this is a secondary development.

ix-vfiT- vn'

Fig. 9. — Wing of Protoplasa fitchii.

Wing of a Leptid. — A specimen of one of the snipe-
flies, Leptidce, will be given the student for examination with
a hand lens. Note the deep furrow between veins I and III ;
along the bottom of this furrow vein II extends. Vein II,
therefore, is a concave vein. Note that this corrugation
stiffens the wing. It is along the costal edge that the wing
needs to be strongest, and correlated with this fact we find
that vein II is usually a concave vein.

Make a drawing of a mounted wing of one of the Leptidce.
Note that in the mounted specimen vein II is more or less
concealed by vein III, although the two veins are distinct,
as was seen on the unmounted specimen, studied with a

— 88 —

hand lens. Represent these two veins as slightly separated
in your drawing.

In the description of this wing, state in what respect it is
more generalized than that of Rhyphus, and in what respect
it more specialized.

Wing of an Asilid. — In the description of this wing note a
method of coalescence of veins not exhibited by Rhyphus, and
call attention to each case in which this method of coalescence
occurs in this wing.

Wing of a Bombylliid. — In the study of this wing
especial attention should be paid to the branches of media and
cubitus.

"Wing of an Empidid. — The most striking feature in the
venation of this wing is the courses of the branches of cubitus.

Wing of a Dolichopodid. — This wing will afford the stu-
dent excellent training if he will work over it carefully.

WINGS OF LKPIDOPTERA.

As the wing of Lepidoptera are covered with scales, it is
difficult to determine the nature of their venation without
specially preparing them for this purpose. After a student
has become familiar with the type of venation characteristic
of the order, he can usually determine the nature of any
particular structure by putting a drop of chloroform on the
part of the wing to be examined ; this will render the veins
more distinct for a few seconds. Or the scales can be re-
moved from a small part of the wing with a small, artist's,
sable brush. But when a very careful study of the venation
of a wing is to be made, it should be bleached and mounted
on a card or on a glass slip, in order that it may be studied
with a compound microscope. The following is the method
of bleaching wings : —

i. Remove the wings carefully so as not to break the

-Sy-

frenulum if there be one ;* it is well to remove the patagium
first, f

2. Dip the wings in alcohol in order to wet them.

3. Immerse them for an instant in hydrochloric acid
(muriatic acid). Use for this purpose dilute acid, one part
acid to nine parts water.

4. Put them in Labaraque solution with the upper surface
of the wings down, and leave them there till the color has
been removed from the scales. If a wing bleaches slowly,
the process can be hastened by dipping it in the dilute acid
and returning it to the Labaraque solution from time to time.
This solution can be procured of most druggists. It deteri-
orates if left exposed in strong sunlight. If it cannot be
obtained, use an aqueous solution of chloride of lime.

5. When a wing is bleached, put it in alcohol and leave it
there till after it floats. This is to wash off the I,abaraque
solution. The wing can then be mounted on a card. But
it is better to mount it as described below.

6. Transfer the wing to a clearing mixture, if it is to be
mounted in balsam, and leave it there five or ten minutes.
This is to remove any water there may be on it. A good
clearing mixture can be made by mixing two parts by
measure of carbolic acid crystals and three parts of rectified
oil of turpentine.

7. Put the wing on a glass slip with considerable clearing
mixture under it to avoid bubbles ; put Canada balsam on
top, and cover with thin glass. In the case of small wings,
it is best to transfer them from one solution to another, and
to the glass slip by means of a camel's-hair brush. £

* The frenulum is a strong spine or bunch of bristles borne by the hind wing at
the humeral angle in most moths.

t The patagia are the paraptera of the mesothorax , they are scale-like append-
ages at the bases of the fore wings.

\ In the case of very small wings, as those of Tineids, the very fine veins are
nure distinct when mounted in glycerine than when mounted in Canada balsam.

— yo-

Wings bleached and mounted in this way make an im-
portant addition to a collection. The slides should be care-
fully labelled ; and the insect from which the wings were
take should be kept with the slide. It is our practice to re-
move always the wings from the right side, and then to
mount the slide in the collection at the right of the insect
from which the wings were taken. Uniformity in this
respect adds greatly to the appearance of the collection.

Wings of Hepialus. — Mounted specimens of the two
wings of one side of a moth belonging to the genus Hepialus
will be furnished the student for study. Be very careful of
the specimens, as moths of this genus are rare in this country.

In the description of these wings, note especially a strik-
ing difference between them and the wings of Diptera as re-
gards the nature of vein II.

The membraneous lobe near the base of the inner margin
of the fore wing is the jugum . This extends under the
costal margin of the hind wing, while the greater part of the
inner margin of the fore wing overlaps the hind wing. This
arrangement assures the acting together of the two. wings.

Wings of a Cossid— Mounted wings of one of the Cos-
sidce will be furnished the student for study.

In the description, state the most important differences be-
tween these wings and those of Hepialus, and make a com-
parison between the structure of vein VIII in the Lepidoptera
and in the Diptera.

Wings of the Monarch Butterfly. — The student will
be furnished with specimens of the two wings of one side of
the monarch butterfly, Anosia plexippus.

Study the fore wing first. In the description of this wing
explain the significance of the three short spurs that project
into the distal end of the large cell near the middle of the
wing.

In the description of the hind wing, discuss the changes
that have taken place in media.

— gi —

Wings of Frenate Moths. — Specimens of moths belong-
ing to the family Nociuidcc will be furnished as illustrations
of I^epidoptera in which the frenulum is well developed.
Two specimens, a male and a female of the same species,
will be given the student.

Remove the wings of the right side of the female, and
bleach and mount them.

Figure and describe these wings.

Remove the wings of the right side of the male, and
bleach and mount them.

Figure and describe these wings.

Describe the secondary sexual distinction exhibited by the
wings of this species.

How could one of these types have been derived from the
other ?

Study the wings of the male that have not been bleached
and note the frenulum hook on the fore wing, which receives
the tip of the frenulum. It may be necessary to remove
some of the hairs from the base of the wing. Use a small
sable brush for this.

Study the unbleached wings of the female and note the
absence of a frenulum hook.

Compare the hind wing of the monarch butterfly with the
hind wings of these moths and discuss the differences
between them.

INDEX AND GLOSSARY.

Abdomen (ab-do'men), 9.

Abdomen, parts of the, 24, 56.

Ad, the ending, 2.

Adipose tissue (ad'i-pose), 33.

Alimentary canal, 33.

Anal angle, 86.

Anal furrow, 78.

Anal prolegs, 30.

Anal veins, 79.

Angles of wings, 86.

Anosia plexippus ( A-no'si-a plex-

ip'pus). 57, 90.
Antecoxal piece, 55.
Antennae ('an-ten/nae), 14, 49, 59.
Antennal nerves, 43.
Anus (a'nus), 27.
Aorta (a-or'ta), 41.
Apex of the wing, 86.
Apis mellifica (A'pis mel-HPi-

ca), 71.
Asilid (As'i-lid), wing of an, SS.
Aspects of appendages, 6.
Aspects of the body, 5.
Attachments of the alimentary

canal, 34.
Auditory organs, 25.
Basiproboscis, 71.
Bleaching wings, 88.
Blood-vessels, 40.
Bombylliid (Bom-byl'li-id), wing

of a, 88.
Branched suspensory muscle, 36.
Branched veins, 77.
Cardinal directions, the six, 2.
Cardo (car'do), 16, 49, 72.
Caudad (cau'dad), 2.
Caudal (cau'dal), 2, 4.
Cells of the wings, numbering of

the, 84.
Cephalad (ceph'al-ad), 2.
Cephalic (ce-phal'ic), 2, 4.
Cerci (cer'ci), 27.
Chitine (chi'tine), 9.
Chloral hydrate, 29
Cicada dorsata (Ci-ca'da dor-

sa/ta), 67.
Circulatory system, 40.

Claspers, 66.

Clypeal (clyp'e-al) suture, 47.

Clypeus (clyp'e-us), 12, 47, 58.

Compound eyes, 10, 48, 57.

Concave veins, 84.

Confluent, 52.

Construction of the terms used, 2.

Convex veins, 84.

Corydalis cornuta (Co-ryd'a-lis

cor-nu'ta), 28.
Cossid (Cos'sid), wings of a, 90.
Costa (cos/ta), 78.
Costal margin, 86.
Coxa (cox'a), 23.
Coxal cavities, 51.
Cross-veins, 76.

Crura cerebri (cru/ra cer'e-bri), 43.
Cms, 43.

Cubitus (cu'bi-tus), 78.
Cuticle, 40.

Dextrad (dex'trad), 3.
Dextral (dex'tral), 2.
Digitus (dig'i-tus), 50.
Diptera, wing-veins of, 86.
Directions for the study of wings,

86.
Dissosteira Carolina (Dis-sos-teir-

ra car-o-li/na), 21.
Distad, (dis'tad), 5.
Distal (dis'tal), 5.
Distiproboscis, 71.
Dog-day Cicada, 67.
Dolichopodid (Dol-i-cbop'o-did),

wing of a, 88.
Dorsad (dor'sad), 3.
Dorsal (dor/sal), 2.
Dorsimeson (dor-si-mes'on ), 5.
Dvtiscus (Dy-tis'cus), 54.
Ectad (ec'tad), 5.
Ectal (ec'tal), 5.
Egg-guide, 26.
Ejaculatory duct, 38.
Elytra (el'y-tra), 53.
Empidid (Em'pi-did), wing of an,

88.
Entad (en'tad), 5.
Ental (eu'tal), 5.

94 —

Entire, 52.

Epicranium (ep-i-cra'ni-um), n,

47, 53.
Epimeron (ep-i-me/ron), 19, 21,

5i, 53. 55, 62.
Euipharynx (ep-i-phar'ynx), 6o,

'70.
Epipleura (ep-i-pleu/ra), 51, 53.
Episternum (ep-i-ster'num ), 18,

19, 21, 5f, 53, 55, 62.
Evolution and Taxonomy, 81.
False claspers, 66.
Fat, 33.

Femur (fe/mur), 23.
First, second, third, etc., 7.
Flabellum (fla-beFlum), 73.
Frenate moths, wings of, qi.
Frenulum (fren'u-lum), 89.
Frenulum hook, 91.
Front, 12.

Frontal ganglion, 43.
Frontal ridge, 47.
Furcula (fur'cu-la), 27.
Galea (ga/le-a), 16, 50, 72.
Ganglia (gan'gli-a), 32.
Gastric caeca (gas'tric cae'ca), 34.
Genae (ge'nae), 12, 48, 58.
Generalized, 76.
Glossa (glos'sa), 50, 73.
Great- dorsal-recti-muscles, 45.
Great-ventral-recti-muscles, 45.
Gula (gu'la), 13, 48.
Gular (gu/lar) sutures, 4S.
Harpagones (har-pa-go'nes), 66.
Head, 8.

Head, parts of the, 10, 47, 57.
Hepialus (He-pi'a-lus), wings of,

90.
Hexagenia (Hex-a-ge/ni-a), 79.
Humeral angle, 86.
Hypopharynx (hy-po-phar'ynx),

15, 50- 70.
Inner margin, 86.
Intermediate, 7.
Interrupted, 53.
Intestine, 34.
Intima (in'ti-ma), 40.
Jugular sclerites (ju'gu-lar scle/-

rites), 19.
Jugum (ju'gum), 90.
Kidneys, 34.

Krauss, Dr. William C, 43.
Labella (la-beFla), 70, 71.
Labial palpi (la/bi-al paKpi), 15,

50, 60, 70, 74.

Labium (la/bi-um), 14, 50, 60, 68,

70, 73-
Lacinia (la-cin/i-a), 16, 50.
Labrum (la'brum), 14, 49, 59, 68,

69, 72.
Large intestine, 34.
Laterad (lafer-ad), 3.
Lateral filaments, 30.
Lateral (lat/er-al), 3.
Legs, 23, 55.

Lepidoptera, wings of, 88.
Leptid (Lep/tid), wing of a, 87.
Leptis (Lep'tis), 85.
Ligament of the viscera, 37.
Ligula (lig'u-la), 15, 50.
Limitations to. accuracy, 7.
Locusts, 8.

Longitudinal veins, 76.
Lyonet, 44, 45.

Malpighi (Mal-pe'ge), 34.
Malpighian vessels (Mal-pe'ghi-

an or Mal-pig'hi-an), 34.
Mandibles (man'di-bles), 14, 49,

60, 68, 70, 72.
Mandibular scrobe, 49.
Margins of wings, 86.
Masticatory organs of the proven-

triculus, 39.
Maxillae (max-il'lae), 14, 16, 49,

60, 68, 70, 72.
Maxillary palpus (max'il-la-ry

paFpus), 16, 60, 69, 73.
Maxillary tendons, 71.
May-fly, wing of a, S2.
Media '(me'di-a), 78.
Mediproboscis, 71.
Melanoplus femur-rubrum ( Me-

lan/o-plus fe/mur-ru/brum), 8.
Mentum (men/tum), 15, 73.
Mesad (mes'ad), 5.
Mesal (mes'al), 5.
Meson (mes'on), 5.
Mesonotum ( 111 es-o-no/ turn), 20.
Mesosternum ( mes-o-ster/num),

20, 52.
Mesothorax (mes-o-tho'rax), 19,

52, 6r.
Metauotum (met-a-no/tum ), 20.
Metasternum (met-a-ster/num),

20, 54.
Metathorax (met-a-tho'rax), 19,

54, 63.
Monarch Butterfly, wings of the,

90.

V

^•5j?i'S2v*'?<*'