EXCHANGE

1 EXL1BRIS

BIOLOGY
LIBRARY

A CONTRIBUTION TO THE KNOWLEDGE OF

THE INTERNAL ANATOMY OF

TRICHOPTERA

A Thesis

Presented to the Faculty of the Graduate School of

Cornell University for the degree of

Doctor of Philosophy

By

HAZEL ELISABETH BRANCH

Reprinted from the Annals of the Entomological Society of America
Vol. XV, pp. 256-280

Columbus, Ohio: September, 1922

A CONTRIBUTION TO THE KNOWLEDGE OF

THE INTERNAL ANATOMY OF

TRICHOPTERA

A Thesis

Presented to the Faculty of the Graduate School of

Cornell University for the degree of

Doctor of Philosophy

By
HAZEL ELISABETH BRANCH

Jfc

Reprinted from the Annals of the Entomological Society of America
Vol. XV, pp. 256-280

Columbus, Ohio: September, 1922

BIOLOGY
LIBRARY

A CONTRIBUTION TO THE KNOWLEDGE OF THE
INTERNAL ANATOMY OF TRICHOPTERA.*

By HAZEL ELISABETH BRANCH,
Wichita, Kansas.

NERVOUS SYSTEM. f

The nervous system of the trichopterous larvas is comparatively
primitive and agrees with that of the lepidopterous larvas in the number
of pairs of ganglia and also resembles, in some respects, the arrangement
in relation to the body segments. Exclusive of the ganglia in the head,
which are normal in number and position, there are three pairs for the
thorax and eight pairs for the nine abdominal segments, the seventh
abdominal segment being the most posterior in which ganglia are found.

In the head of Limnophilus indimsus the supra-cesophageal ganglia
are situated with their anterior margin on a line immediately posterior
to the eyes. The combined width of the ganglia is about one-half that
of the head. Each ganglion gives off laterally and in a forward direc-
tion, an optic nerve which branches to supply each of the simple eyes
of the visual area. In front of the junction of the two ganglia is the
frontal ganglion, small and shield shaped, connected to the supra-
cesophageal ganglia by a pair of arms. Proceeding from each arm of the
frontal ganglion, close to its attachment with the supra-cesophageal
ganglion, is a nerve which extends forward and sends an outer branch to
the labrum, and an inner branch to the dorsal region of the buccal
cavity, see Plate XIV, Figs. 4 and 5, at lb x and b. Between the point
of attachment of the arm of the frontal ganglion with the supra-cesoph-
ageal ganglion, and the optic lobe, (opt), is the slender antennal nerve
rising from the anterior margin of the ganglion and possessing a fellow
in like position upon the other ganglion, see Plate XIV, Figs. 4 and 5
at ant. Upon its posterior face, each ganglion gives rise to a pro-
tuberance from which issues a nerve that converges toward its fellow
and meets it upon a median line. At this union a small
ganglion is formed and to this are also joined, the nerves
coming from the sympathetic ganglia. These sympathetic ganglia are
single, one upon each side of the oesophagus and possessing a nerve
connection with the posterior protuberance of the supra-cesophageal
ganglion of its respective side, See Plate XIV, Figs. 4 and 5.

The recurrent nerve of the frontal ganglion extends in a posterior
direction between the supra-cesophageal ganglia and the oesophagus

* A contribution from the Department of Entomology, Cornell University,
prepared under the supervision of Dr. O. A. Johannsen, to whom and also to Dr.
J. G. Needham and Dr. J. T. Lloyd, I wish to express my gratitude for the valuable
assistance rendered.

t In gross dissection, hot water killing and Gilson's fixing solution were found
to be most advantageous.

2o6

1922] Branch: Internal Anatomy of Trichoptera 257

and fuses with the nerve which extends posteriorly from the ganglion
situated at union of the nerves from the posterior protuberances of the
supra-cesophageal ganglia and the sympathetic ganglia of each side.

From the ventral face of the supra-cesophageal ganglia, arises a
pair of connectives, the crura cerebri, which connect the supra-cesoph-
ageal ganglia with the sub-cesophageal ganglion.

Immediately in front of the union of the crura cerebri with the
supra-cesophageal ganglia, the cesophageal ring of the tritocerebrum
arises. This is a loop w r hich encircles the oesophagus and has its ends
connected with the supra-cesophageal ganglia, see Plate XIV, Fig. 5 at or.
The supra-cesophageal ganglia does not fit closely upon the oesophagus
normally, but leaves some space laterally and ventrally for the expan-
sion of the tube in feeding. Faivre 1857, states that the supra-cesoph-
ageal ganglia possess the seat of motive power and will power and Binet,
1894, strengthens this statement by the results of his own experiments
which show that an insect will live for months with the supra-
cesophageal ganglia removed but will not eat unless the food is placed
in its mouth as it has no power to move toward the food.

The sub-cesophageal ganglion is situated slightly back of the
posterior margin of the supra-oesophageal and below the oesophagus
but well within the limits of the head cavity. This ganglion gives off
three pairs of nerves, the most ectal and dorsal of which extends in a
forward and upward direction and, upon a level with and in front of the
frontal ganglion, branches. One branch extends to the base of the
labrum, see Plate XIV, Figs. 5 and 6 at Ib2, while a second branch
extends to the dorsal side of the mandible, see Plate XIV, Figs. 5 and 6
at md2. The second pair of nerves from the sub-cesophageal ganglion
arises ventrad of the first pair and extends forward also branching.
The ectal branch of each nerve reaches the musculature of the maxilla,
mxl ; and an ental branch divides and one part goes to the maxillary
sclerite and the other to the labium, see Plate XIV, Figs. 5 and 6, at mx2
and H2. This pair is connected by a nerve just below the frontal ganglion,
and the cross nerve bears a small median ganglion. The third pair of
nerves is ventrad of the second pair and extends forward directly to the
labium, which it innervates, lil.

The above description is made from several dozen specimens of the
species Limnophilus indimsus Walker. The head ganglia of the other
species studied do not vary materially.

Posteriorly the sub-cesophageal ganglion gives off a pair of com-
missures which connect to the first thoracic* ganglion lying in the
prothorax. In the thorax and abdomen there is much variation among
the species as to the relation of the ganglia to their respective seg-
ments. Upon observation of these three species (Limnophilus indivisus
Walker, Hydropsy diodes anal is Banks and Phryganea interrupta Say,)
two centers of fusion will be found, one in the thorax and one in the
abdomen at the posterior end of the chain. As above stated, there are
three thoracic and eight abdominal ganglia. The prothoracic and

* Each ganglion of the thorax and abdomen is a pair of fused ganglia.

5077.13

258 Annals Entomological Society of America [Vol. XV,

mesothoracic ganglia are about the same size as the sub-cesophageal
ganglion and are each situated equidistantly from the anterior and
posterior margins of the segments and this condition prevails for the
three species. The meta thoracic ganglion is larger than those of the
preceding segments and its position is not the same in the different
species for it is here that the thoracic fusion point occurs. In Phryganea
interrupta the ganglion is centrally located with the ganglion of the
first abdominal segment just within the posterior border of the meta-
thorax. In Limnophilus indivisus, the metathoracic ganglion has
migrated forward and the first abdominal ganglion has followed until
the latter occupies the central position with the metathoracic ganglion
well in the front half of the segment. In Hydropsychodes analis, the
condition is the same as in L. indivisus.

In the abdomen of the three species the positions of the ganglia
are more noticeably variable. In P. interrupta the first abdominal
segment bears at its posterior margin, the ganglion of segment two
and segment two is void of any ganglion, but receiving its innervation
from its respective ganglion located in segment one. The ganglia of
segments three, four, five and six occur in their respective segments
near the front margins. Segment seven bears in its front half, two
ganglia; these are the ganglia for segments seven and eight and they
are very closely united, but not fused at all, Plate XIV, Fig. 2. In
L. indivisus, the ganglion of segment two occupies a central position
in segment one, indicating a forward migration. Segments three, four
and five have their ganglia in the front half of the segment as in P.
interrupta. In segment six all the ganglia of the three segments, six,
seven and eight, are placed; those relating to segments seven and eight
are closely united, practically fused, and take a position in the posterior
half of the segment. The ganglion for segment six is in the anterior
half of the segment, Plate XIV, Fig. 1. In H. analis we find an arrange-
ment in the abdomen which varies from that which Pictet, 1834,
observed in Hy dropsy che, for he saw all the ganglia here upon the
divisions between the segments. In this particular species, the ganglion
for segment two is in segment one as usual, and the ganglion for segment
three is on the margin between segments two and three which is a
forward migration. The ganglion for segment four is in front of the
center of the segment and the ganglion for segment five is back of the
center of its respective segment. In the sixth abdominal segment
are three ganglia, for segments six, seven and eight respectively and all
are in a line and practically fused, Plate XIV, Fig. 3.

The thoracic ganglia and the abdominal from one to six innervate
their respective _segments and appendages, the seventh abdominal
appears to have only one pair of nerves which extend backward into
segment seven, the eighth abdominal ganglion innervates segment
eight and nine, as well as the swimmerets. which extend out from seg-
ment nine. There are various ways for the eighth abdominal segment
to innervate segment nine. In P. interrupta and H. analis it sends a
nerve directly to the segment, but in L. indivisus the nerve which
extends to segment eight branches and sends a branch to segment

1922] Branch: Internal Anatomy of Trichoptera 259

nine, this arrangement leaves one less pair of nerves arising from ganglion
eight in L. indivisus than in P. interrupta or H. analis.

Upon a comparison of the three Figures, Nos. 1, 2 and 3, Plate XIV,
a sequence of fusion is evident. This sequence places P. interrupta
as the most generalized and H. analis as the most specialized and L.
indi-dsiis as intermediate. Vorhies, 1905, has described the nervous
system of Platyphylax designatus Walker and it falls between P.
interrupta and L. indivisus for the ganglia of the seventh and eighth
segments have migrated so that the ganglion for segment seven is just
inside the posterior margin of segment six and the ganglion for segment
eight remains in segment seven, but very close to its anterior margin.
Betten, 1901, in his description of Molanna cinerea does not show it
to vary from P. designatus. Pictet, 1834, figures Phryganea striata
Fab. to fall between P. designatus and L. indimsus with the ganglia
for segments six, seven and eight in segment six, but ganglia seven
and eight not fused. Klapalek, 1888, does not note any variation of
position, but merely gives the number of ganglia and their general
distribution.

From the above it seems reasonable to think that the nervous system
of the order will reveal grades of consolidation of the ganglia which may
have a decided bearing upon classification.

REPRODUCTIVE SYSTEM.

The writer has done very little in this system beyond the mere
location of the organs, for the matter seems to have been given adequate
attention by Zander, 1901, Lubben, 1907, and Marshall, 1907. As
to the period of the appearance of the organs there is a difference of
opinion. Pictet, 1834, Klapalek, 1888, and Vorhies, 1905, make the
statement that the organs do not appear until near the period of pupa-
tion or at least in a very old larva; Lubben, 1907, discusses conditions
in a transforming larva, while Marshall, 1907, speaks of the condition
of the organs in the youngest larva he had, but does not give the stage.
In all the specimens observed by the writer, the gonads appear in
the early forms, showing clearly both in gross dissection and sections.
In P. interrupta taken in October and H analis taken in late December
from under the ice in streams, the gonads are distinct and developed
far enough' so that tubules may be seen, Plate XIV, Fig. 7. This period
is long before there are any signs of pupation either in case or larva.

Within the species two shapes of gonads appear. In P. interrupta
some are elongate and flat, while others are spherical. This seems to
point to a sex differentiation, the elongate one probably destined to
become female organs and the spherical ones male organs, Plate XIV,
Fig. 2. In gross dissection in L. indivisiis only one kind of a gonad
was observed, this circular and plate-like of five pairs of tubules. Plate
XIV, Fig. 1, at gd. In each gonad there are two outgrowths or attach-
ments; one from the outer side and extending to the ventral body wall
of the second abdominal segment and resembling a supporting thread
or tissue, the inner side outgrowth appears as a duct and the tubules
of the gonad may be seen converging toward the head of this duct.

260 Annals Entomological Society of America [Vol. XV,

The duct .extends in a posterior direction and extends to the ventral
side of the eighth segment, where it is lost. Lubben, 1907, shows that
these ducts pass into external, sculptured plates in the eighth segment
but I have been unable to find any such structure or any opening what-
ever at this point on any of the specimens. In H. analis the gonad
is oval, but appears spherical in frontal section as the long axis of the
gonad is at right angles to that of the body of the larva. The gonads
of the above three species are in pairs and lie in the fifth segment of the
abdomen Betten, 1901 finds the gonads for M. cinerea in segment
four; Lubben, 1907, records Anabolia nervosa and Limnophilus stigma
as having the organs in segment five, Rhyacophila septentrionis and
Brachycentrus montanus in segment four. Klapalek, 1888, gives the
gonads a general location of segment three, but neither literature nor
my own observations uphold this statement. From a compilation
of records the position appears to be in either the fourth or fifth
segment.

ALIMENTARY CANAL.

General description: The alimentary canal, in the order Trichoptera,
passes as almost a straight tube from buccal cavity to anus. Pictet,
1834, figures the tube as practically undifferentiated in its shape and
only varying slightly in size at the extreme ends. Klapalek, 1888,
states that the regions merge imperceptibly into each other. Although
this condition may be true in a specimen gorged with food, the writer
has never seen a specimen where the three main divisions of stomodeum,
mesenteron and proctodeum were not distinctly marked one from the
other. The lack of convolutions as are normal in the alimentary canals
of insects which are herbivorous, is unusual, as Siltala, 1907, shows that
the order is in the main herbivorous and yet this general type of a
straight tube prevails. There are a few semi-carnivorous species, but
even here there is no variation from the above condition. The assimi-
lative area is increased by an unusual width in proportion to that of
the body, for in many places and especially the mesenteron, the width
is equal to one- third and frequently more than one-third the width of
the abdomen. Another device adds to this area or surface for the wall
of the mesenteron is folded into transverse ridges which increase the
surface by three times that actually occupied by the wall, Plate XV,
Fig. 10. These folds are deeper in the strictly herbivorous types, such
as L. indivisus, than in those which are more or less carnivorous, as
H. analis. We will pass now to a discussion of the alimentary canal
in the three species. Hydropsychodes analis Banks, Plate XV, Figs.
7, 8 and 9. The surface of the stomodeum of the alimentary canal
presents a silvery appearance, due to the peritoneal covering of the
muscles which surround and control the activities of this portion of the
canal. This portion is much darker than the remainder of the canal,
due to the food within. If this be cleaned, the wall appears transparent.
Beneath the peritoneal membrane can be seen the longitudinal muscles
arranged in pairs in six equi-distant places around the canal. Under-
neath these longitudinal muscles lie the circular muscles, which are so

1922] Branch: Internal Anatomy of Trichopter a ''261

heavy and thick that they give the canal the appearance of having
great rings around it. The stomodeum is composed of four parts,
namely: buccal cavity, oesophagus, crop and proventriculus. The buccal
cavity is large, including half the depth of the head capsule, it narrows
rapidly and passes over into a slender tube which passes beneath the
supra-cesophageal ganglia as the oesophagus. The oesophagus extends
backward through the head and prothorax with only slight expansion.
At the posterior margin of the prothorax it begins to enlarge and extends
through the length of the mesothorax with a diameter one-third that
of the thorax and four times the diameter of the oesophagus in the
prothorax. This is the crop. At the posterior margin of the meso-
thorax the stomodeum is suddenly constricted to about half its width
and within a longitudinal distance of .5 mm. suddenly enlarges to form
a cylindrical structure, the wall of which becomes resistant to dissecting
instruments and is very hard. The circular muscles are larger and
heavier in this region and inside the tube are chitinized teeth. This
portion is the proventriculus, which functions as a grinding organ
and possibly as a straining device.

The cylindrical shape ends suddenly at the posterior margin of the
metathorax and the transition into the mesenteron is well indicated by
change in color, texture and structure of the wall and by a deep fold.
The proventriculus pushes into the forward end of the mesenteron and
forms there an cesophageal valve. The mesenteron folds up over the
proventriculus and causes a distinct line to appear between the two
portions. The silvery tone of the wall is lost at this juncture; the
longitudinal muscles break up to form a layer of muscles around the
mesenteron and this layer extends the full length of the mesenteron.
Beneath these muscles can be seen the very thin layer of circular muscles.
The mesenteron enlarges at its beginning to at least a third the diameter
of the abdomen of the larva and increases slightly toward the fourth
segment and then returns to its width at the beginning before it reaches
its length. This division arises at the posterior end of the metathorax
and extends through the length of the abdomen as an almost straight
tube, varying only as above in diameter, circular in cross section, and
possessed of an extremely thick wall, but one that is easily torn apart.
In the sixth segment the mesenteron becomes about two-thirds the
diameter at its beginning and passes over into the proctodeum. The
proctodeum is composed of intestine, both large and small, and the
rectum. The mesenteron pushes into the intestine in much the same
manner that the proventriculus pushes into the mesenteron, but the
distance is not as great and the valve formed is not a distinct one in this
species, although the division between the two main divisions of the
canal is clearly marked. At the point where these two portions meet,
the Malpighian tubules, of which there are six, make their appearance
upon the surface. These tubules are situated upon the lateral and
ventral faces of the alimentary canal and the dorsal face is void of them ;
however, the first pair may be easily seen from a dorsal view, each mem-
ber of this pair lies upon the upper portion of the lateral face and
extends forward through the abdomen and into the metathorax. Slightly

262* ''Annals Entomological Society of America [Vol. XV,

below the first pair, the second pair arises and extends, each member
of the pair upon its respective side of the alimentary canal, forward
for the remaining distance of the sixth segment where it turns back-
ward and taking an upward and lateral direction, with regard to the
intestine, curves and coils about in the lower part of the abdomen back
of the sixth segment. The third pair of tubules is situated upon the
venter about equidistant from each other and from the corresponding
members of the second pair. This third pair extends backward
immediately and each member comes to lie beneath and to the side of
the intestine, intertwining with the corresponding member of the
second pair. The tubules are irregular in outline, appearing like small
oval beads strung upon a thread. In general color they are a pale,
clear yellow, but blotched at irregular intervals with a kidney-brown
pigment. They weave in and out among the fat bodies and tracehae,
and into blood sinuses to perform their function of the" removal of
nitrogenous waste.

The front end of the intestine is cup-shaped with the larger end
forward. This portion represents the small intestine. The tube
grows smaller as it proceeds toward the caudal end. but in the seventh
segment is greatly constricted; it enlarges immediately and passes
through segment eight with a diameter of about a fourth that of the
segment and two-fifths of the diameter of the mesenteron in the first
segment. This portion represents the large intestine.

At the posterior margin of segment eight, the intestine is again
constricted and passes over into the rectum. At this juncture there is a
semi- valve formed by the invaginated walls of the intestine. These
folds become longer and fewer in number and form the blood gills which
lie in the rectum. The rectum extends through the ninth segment.
In some forms examined, the small diameter of the constricted region
at the posterior end of segment seven prevails through the eighth,
widening suddenly at the beginning of the ninth to accommodate the
invaginations forming the blood gills; in other forms the widening is
gradual through the eighth and passes over gradually into the rectum
without any noticeable constriction. The wall of the small intestine
is heavy and surrounded with circular muscles. It becomes thinner as it
extends toward the large intestine. When the rectum is reached the
wall is exceedingly thin and almost transparent. Through the wall
can be seen the four pockets or invaginations which form the blood gills,
and into these muscles extend from the lateral and ventral walls at the
conjunctiva between segments eight and nine. The rectum now serves
a double function, that of elimination of fecal matter and secondarily
that of respiration, when oxygen cannot be obtained by means of the
tracheal gills. These blood gills have no tracheae running into them
as a glycerine mount of the caudal portion of a fresh specimen clearly
demonstrates. They function, when the larva is out of the water, by
protruding themselves through the T-shaped anus, in which state they
are filled with blood. A detailed account of their structure will be
found elsewhere in this paper.

1922] Branch: Internal Anatomy of Trichoptera 263

Limnophilus indivisus Walker,* Plate XV, Figs. 1, 2, 3 and 5.
In this form the oesophagus passes from the buccal cavity into the head
region where it is a small tube and continues through the prothorax.
The crop is absent in this form and the oesophagus passes immediately
into the proventriculus. Here the chitinized "teeth" upon the lining
such as we find in H. analis are lacking. They are not needed, as the
form is strictly herbivorous and H. analis is semi-carnivorous. The
oesophagus begins to enlarge at the posterior edge of the prothorax to
form the proventriculus, which lies in the mesothorax. It is silvery in
appearance and dark colored, but not resistant to the needle owing
to the lack of chitinized teeth within. The proventriculus possesses
the six pairs of longitudinal muscles and the circular layer, but these
are not as heavy as in H. analis. At the posterior margin of the
mesothorax the proventriculus constricts slightly and passes over into
the mesenteron. This position is contrary to the usual division level
for these two portions of the alimentary canal, but the oesophageal
valve occurs here and the character of the wall changes to a light pale
color,, is thicker in cell depth and the six pairs of muscles from the
proventriculus form the characteristic layer around the new division.
From these characteristic markings there can be no doubt as to this
transition. The oesophageal valve is normal, Plate XV, Figs. 2 and 3
show it as a complete imagination of the wall, in a fold of eight pro-
jections

The mesenteron takes its beginning in the mesothorax and increases
in diameter as it passes through the metathorax. It may be slightly
constricted in the first abdominal segment although it frequently
passes without any change of contour. It passes through the abdomen
at its diameter of one-third that of the abdomen and extends to the
sixth segment. Here the transition into the intestine occurs and the
juncture is marked by the presence of the six Malpighian tubules,
in the same arrangement as in H. analis. The tubes are longer, however,
and the first pair does not extend into the thorax, but turns backward
in the first abdominal segment and returns to the seventh. The
second pair frequently extends as far as segment three and then returns
to segment eight. The third pair may continue forward through
segment six before turning backward. The junction between mesenteron
and intestine is marked by a decided valve not found in H. analis
and similar to the oesophageal valve. A section showing this structure
is on Plate XV, Fig. 10. The intestine at its forward end is also cup-
shaped and, at the constriction between small and large intestine,
possesses a valve formed by the in vagina tion of the intestinal wall.
(Plate XV, Fig. 5). Along the intestine are six muscle bundles which
seem to control the initial position of the Malpighian tubules. Marchal,
1892, considers the tubules as being capable of motion and perhaps
these muscles have some part in that action. These muscles likewise
support the front edge of the rectum into which the large intestine
telescopes.

* This species is selected for a comparison with H. analis, as the two rep-
resent widely divergent forms.

264 Annals Entomological Society of America [Vol. XV,

Phryganea interrupta Say* Plate XV, Fig. 11.

In P. interrupta, the oesophagus passes through the head as a
narrow tube and enlarges toward the posterior margin of the prothorax
to form a crop of small dimension which is marked from the proven-
triculus by a slight constriction. The proventriculus occupies the
meso and metathorax in length and practically fills the whole of the
body cavity in this region, it presents the silvery surface as in the
other forms and the longitudinal and circular muscles are evident. The
posterior end of the proventriculus extends over into the first abdominal
segment and here is constricted suddenly and passes through this seg-
ment as a small tube about one-fourth the diameter of the proventriculus
in the mesothorax. This constriction is so long that the longitudinal
muscles of the proventriculus do not follow the tube but span the dis-
tance from the beginning of the constriction to the surface of the
mesenteron and can be seen as threads across the open space. f

The mesenteron is the same as in the other forms and passes over
into the intestine of the proctodeum in the sixth segment where the
Malpighian tubules arise. These do not always assume the same posi-
tions, which is further evidence of Marchal's theory on their mobility.
Marchal, 1892. The intestine extends through segments six and seven
and at the anterior margin of the eighth there is a constriction as the
intestine passes over into the rectum. The rectum gradually grows
smaller as it nears the anus. The anterior portion of the intestine has a
heavy musculature and the lower part is ridged longitudinally and these
ridges become more prominent in the rectum and form four longitudinal
columns which continue to the anus.

HISTOLOGY OF THE ALIMENTARY CANAL. J

In this work the writer has divided the material into two parts:
that dealing with cellular structure and that relating to the musculature
of the canal. The condition in H. analis is taken as a basis of compar-
ison and where L. indimsus differs from the above the condition is noted
and illustrated in the figures.

Buccal cavity: The cells are flat and small with small nuclei The
cavity is heavily lined with chitin.

* This third species is selected on account of its larger size,
f A normal cesophageal valve occurs at the division between proventriculus
and mesenteron.

J In the histological work, both hot Gilson's and hot Bouin's were used with
equal advantage if the material was to be used at once. If more than a month
were to elapse before the material would be used, Bouin's was by far the better
fixative, as those in Gilson's softened rapidly.

Much better results were attained by clearing in xylol than in cedar oil.
An infiltration of not longer than nine hours, including the time in xylol and
paraffin, equal parts, at 52 degrees F., produced the material most easily cut.

Staining in Delafield's haemotoxylin and counterstaining in aqueous %%
eosin produced excellent results as a general stain. For muscles and epithelial
cells, iron haemotoxylin made clearer slides than the above. Paracarmine with
a counter stain of orange G. was especially adapted to digestive epithelial tissue in
L. indivisus.

1922] Branch: Internal Anatomy of Trichoptera 265

Oesophagus: The cells of the epithelium are cubical and the whole
epithelium is lined with a chitinous intima. The basement membrane
is distinct between the epithelium and the muscles surrounding the
resophagus.

Crop: Conditions the same as in the oesophagus.

Proventriculus : The cells of the epithelium do not vary from those
of the oesophagus but the wall itself is thrown into folds and the intima
becomes thick and dense and forms the stomachic teeth, the number of
which is about thirty-six. A cross section of this region shows them
surrounding the cavity At the posterior margin of the proventriculus
is the cesophageal valve which in this form is of peculiar plan. It is
practically double with a strongly chitinized invagination into the pro-
ventriculus and an extremely deep but narrow invagination into the
mesenteron This valve does not completely surround the constriction
between the two divisions. For further details see Noyes 1915. This
valve in L. indimsus is normal and complete. It extends into the mesen-
teron in a fold, the upper part of which is composed of cubical cells with
an extremely heavy intima, while the under portion of the fold although
the cells are cubical become somewhat flattened and the intima reduced
to a thin membrane. The wall changes suddenly into the columnar
structure of the mesenteron with its striated border. At the point
where the intima ceases the peritrophic membrane arises. This is sep-
arated from the epithelial wall of the mesenteron and surrounds the
food in the canal, Plate XV, Fig. 6.

Mesenteron: The epithelium here is similar to that at the posterior
end of the cesophageal valve except that the cells become more col-
umnar. The conditions in function accord with those described in the
dragonfly nymph, Needham, 1907, and need no further discussion
here The wall of the mesenteron is folded as mentioned in the dis-
cussion of the gross anatomy of the canal to produce more assimilative
surface and this condition prevails the entire length of the mesenteron
to the sixth segment. In this same segment the Malpighian tubules
show upon the surface and the mesenteron passes over into the intestine,
Plate XV, Fig. 10 at dep.

Malpighian tubules: At the posterior end of the mesenteron where
the cells are still columnar, the ventral pair of Malpighian tubules may
be seen breaking through the epithelial wall on their way to the surface,
Plate XVI, Fig. 7. Patten, 1884, in his embryological investigation of
the Trichoptera shows that these tubules are evaginations of the proc-
todeum before the wall of the forming mesenteron is joined with that
of the proctodeum. Further evidence of this is seen in sections of the
intestine further back where the tubules may be seen forming within
the epithelial tissue of the intestinal walls. The cells are still columnar
but the presence of intima and the Joss of the striated border indicate
that this is no longer mesenteron, Plate XVI, Fig. 6. The Malpighian
tubules are composed of large cells/ glandular in appearance, with a
large nucleus in the center of the /cell. The pigment so noticeable in
gross structure now becomes morel evident and stains darker than the
nucleus and is not confined to a given region of the cell. There are three

266 Annals Entomological Society of America [Vol. XV,

distinct layers; upon the inside is the lining or the intima, then the
large celled wall and the covering which is muscular, Plate XVIII,
Figs. 7 and 8. The dorso-lateral and lateral tubules reach the surface
posterior to the ventral pair.

Intestine: The transition to intestine in H. analis is accomplished
with a mere constriction and change in cellular structure, but in L.
indivisus there is a valve formed as the cesophageal valve is formed, but
reversed in its components, the upper part of the fold is slightly columnar
in its cellular structure but covered with intima in a thin coat, the intima
becomes thicker and the cells cubical as the folds turn toward the
intestinal wall, Plate XV, Fig. 10. At the posterior edge of segment
seven the cubical wall changes and becomes large celled with large
nuclei, Plate XVI, Fig. 2. In H. analis this continues to the anterior
margin of the ninth segment, Plate XVI, Fig. A at 2. At the beginning
of the ninth segment the epithelial wall changes to a cubical condition
which changes only as the wall becomes differentiated into the blood
gills and returns to the cubical condition when this function ceases.
The whole length of the intestine is thrown into six longitudinal folds
which begin in the sixth segment, Plate XVI, Fig. 6, and is traceable
through all the sections to the rectum where the semi-valve occurs
and the four blood gills arise. The folds do not continue into the rectum.
In L. indivisus transition in the eighth segment from the cubical celled
condition to the large celled, which marks the end of the intestine in
this form, is a distinct rectal valve not different in character or forma-
tion from the one into the intestine from the mesenteron; the cells of
the wall of the rectum are large with large nuclei and this condition
continues to within .5 mm. of the anus. It is possible to consider the
rectum of H. analis as beginning at this level and the semi-valve as only
the transition into the blood gills, but the gross anatomical structure
seems to bear the former interpretation.

Musculature: The oesophagus is surrounded with bundles of longi-
tudinal muscles, outside of which is a layer of banded circular muscles
and outside of these six pairs of longitudinal muscles so noticeable in
gross structure. At the anterior end of the proventriculus the inside
layer of longitudinal muscles cease and the proventriculus is imme-
diately surrounded by circular muscles, (see Noyes 1915), which con-
tinue as a sheath of varying thickness for the full length of the alimen-
tary canal as far as the rectum.

Mesenteron: The six pairs of longitudinal muscles break up into a
layer of longitudinal muscles, this layer is composed of large bundles
upon the outside and small ones upon the inside next to the thin cir-
cular muscles. See Plate XVI, Fig. 7.

Intestine: At the anterior end of this division where the cells of
the epithelium are columnar but covered with intima, a heavy circular
muscle arises pushing some of the longitudinal muscles outside and
enclosing the smaller ones, Plate XVI, Fig. 6. In a very few sections
of .008 mm. in thickness this muscular wall is complete, Plate XVI,
Fig. 5. The inner layer of circular muscles becomes thicker as we
advance toward the posterior end of the canal and the inner longitudinal

1922] Branch: Internal Anatomy of Trichoptera 267

muscles have formed themselves into the characteristic six pairs and
those pushed to the outside of the outer circular muscles have ceased,
Plate XVI, Fig. 4. This heavy outer circular muscle comes to an end
in the seventh segment, leaving the six longitudinal pairs as the exterior
layer, Plate XVI, Fig. 3. This condition prevails throughout segment
eight, Plate XVI, Fig. 2, and past the semi- valve into the gill chamber
of the rectum, Plate XVI, Fig. 1. For a diagram of this musculature,
see Plate XVI, Fig. A, the levels drawn are numbered as the figures
which are taken in cross section at these same levels. The musculature
of L. indivisus does not vary from this description based upon H.
analis, with the exception that in the mesenteron the longitudinal
muscles are of a single layer, Plate XVI, Fig. S. The blood gills of
H. analis rightfully belong to the discussion of the histology of the
alimentary canal, but their structure is sufficient to claim for them a
separate division of this paper.

Blood Gills of Hydropsychodes analis Banks.

Protruding from the T-shaped anus, Plate XV, Figs. 8 and 9,
Plate XVII, Fig. 1, are often seen four transparent, greenish, finger-like
appendages, Plate XIV, Fig. 3. These are protruded beyond the
limits of the anus when the larva is out of the water crawling upon
the rocks, or may be artificially protruded by pressure upon the abdomen
in the caudal region. Pictet, 1834. states that these appendages contain
tracheae. There are muscles leading into the gills which might be
mistaken for tracheae if the microscope were not of high magnification.
Dufour, 1847, figures these gills as appendages from the rectum into the
body cavity, but without trachea?. This error of Dufour is easily under-
stood when the larva is dissected, for it is almost, if not quite, impossible
to open a larva from the dorsal side and not cut into the rectum so
that these gills float out as though appendages from it. It is only
when a lateral opening is made that the true internal position is observed.
Fritz Muller, 1888, does not show any tracheae in the gills and Thienman,
1903, and Lubben, 1907, represent these as non-tracheae bearing
structures. In the glycerine mounts of the caudal end of the abdomen
with the gills protruding from the anus, the tracheal tubes are seen to
pass down the sides of the body sending branches to the alimentary
canal and surrounding tissues. Long branches or continuations of the
main tracheal trunks extend into the anal pro-legs or drag hooks,
but in no instance does a single tracheole extend to a gill. In neither
the transverse sections or the longitudinal ones does tracheal structure
appear. Muscles and blood make up the content of the gill. These
gills are in direct communication with the body cavity and it is possible
that, when occasion renders the supply of oxygen insufficient, the blood
rushes from the blood sinuses into these " pockets" and comes with
sufficient force and quantity to extend the gill and push it to the exterior
and an exchange of gases takes place through the wall of the gill. This
action, combined with the lack of tracheae, seems sufficient evidence
upon which to claim the term of true blood ^ills for these structures.

268 Annals Entomological Society of America [Vol. XV,

When retracted these gills lie within the rectum, which serves a
double function, with their distal ends or tips close to the anus and just
barely within the aperture. They may function slightly at this
time.

In surface view the gills present a cylindrical form which tapers as it
extends distally. Upon the surface are transverse ridges which are
bounded by thread-like depressions. These depressions are as deep as
the ridges are wide, for these ridges are made up of rings of cells one
cell deep and one cell wide. At rest these cells are cubical, being as
deep as they are wide, and the depressions are the expansion spaces
between the cells. In expansion this ring of cells becomes narrower
in diameter and the cells themselves wider and more shallow. Compare
Plate XVII, Fig. 6, where the gill is at rest, and Fig. 7, where it is in
extended condition. The tips of the gills are more dense and of a darker
color than the rest of the gill. This condition is due, no doubt, to their
close proximity to the anal aperture and to the fact that they must at
times push their way through waste material in their extension.

To get a clear conception of the formation of these gills, it is necessary
to start with their origin in the wall of the intestine in the ninth segment.
Here the glandular large celled condition of the intestinal wall ceases
and becomes cubical. The wall is thin and the six longitudinal folds
extend inward so as to form a semi-valve at the head of the rectum,
Plate XVII, Fig. 4. Gradually these folds merge into four and form the
four gills. Plate XVII. Fig. 5, shows these longitudinal folds merging
into the gills and being continuous with them. After the formation
of the gill the rectal wall does not again fold, but passes directly to
the anus.

At rest the width of the gill is about one-third its length, which
normally is slightly less than the width of the ninth segment. The gill
is capable of extension to about three times its normal length, and at
this time the wall becomes thin and the cells much longer than deep.
Not all of this extension length is made by the gill itself, as the folds at
the head of the rectum extend and the caudal wall of the rectum itself
is carried down with the gills, Plate XVII, Fig. 7.

The deep cells of the walls of the gills are possessed of large nuclei
and are glandular in appearance. These cells take up about four-
fifths of the diameter of the gill when at rest, leaving the other fifth
for the muscle which extends from the conjunctiva of the lateral and
ventral walls between segments eight and nine. Each gill possesses a
muscle which arises at a corresponding place upon the conjunctiva
and extends to the tip of the gill. Each gill muscle is three branched,
Plate XVII, Fig. 8, and when at rest lines the gill. The gills are covered
with a very thin intima, which is continuous with that of the rectum
and intestine.

GLANDS.

Not all the glands in the body of the trichopterous larvae are con-
sidered here. The writer has confined her attention to the silk glands,
the thoracic glands and the glands in the head, in this last only those in
L. indivisus have been studied.

1922] Branch: Internal Anatomy of Trichoptera 269

The Silk Glands: Of all the glands of the trichopterous larvae
these are the most prominent. They practically fill the part of the
body cavity not occupied by the alimentary canal and extend from the
labial spinneret into the seventh segment. They are opaquely white,
having a pinkish cast in a fresh specimen. Their content is sticky and
if the glands of a fresh specimen be broken in dissection the secretion
will so glue the organs and tissues together as to make further dissection
impossible. This difficulty is remedied by applying Gilson's preserva-
tive to the freshly opened specimen and allowing it to remain for fifteen
or twenty minutes.

Upon the floor and in the center of the anterior edge of the labium
is a spinneret, Plate XVIII, Fig. 3, at sp. This is connected to a single
tube of .2 mm. in length. In this region is the silk press composed of
muscles which control the flow of secretion. This structure does not
differ from the structure of the forms studied by Gilson, 1894, and needs
no further discussion in this paper. At the posterior margin of the
labium this single, slender tube becomes divided into two and passes
ventrad of the nerves extending from the sub-cesophageal ganglion to
the mouth parts. On reaching the ganglion each member of the pair
of tubes passes laterad of the ganglion, Plate XVIII, Fig. 4, and then
approaches its mate and passes with it underneath the oesophagus. At
the posterior margin of the sub-cesophageal ganglion the tubes change
their character from that of a duct to a true gland. In the duct the
cells are small with simple nuclei. Externally the change is marked
with a depression as though a thread were fastened tightly around the
tube. Back of this depression is the gland proper, composed of an
outer wall with an irregularly shaped nucleus in a flattened cell. This
outer wall is two cells in circumference, the cells are hexagonal with
the lateral face in a triangle. The front face of the triangle meets
the posterior face of the triangular side of the other cell, see Plate
XVIII. Fig. 5. Inside of this wall, which is frequently very loosely
applied, is the inner tube consisting of a firm cylindrical wall, where
the secretion is formed and inside of this heavy wall is a narrow tube
through which the secretion passes to the duct, Plate XVIII, Figs.
6 and 6a.

These silk glands lie ventrad of the alimentary canal throughout the
thorax and frequently as far as the second abdominal segment. Finally
they make their appearance at the sides of the alimentary canal and
increase in size They extend to the sixth segment where they turn
forward again and extend to the second and third abdominal segment,
turning backward they reach to the seventh segment where the distal
ends are frequently folded under the intestine or float free among the
various folds of the Malpighian tubules, Plate XV, Fig. 1. For a
detailed description of these glands see Vorhies, 1908.

Thoracic glands: Gilson, 1896, shows Phryganea grandis as possess-
ing three glands or pairs of glands in the thorax, one pair to each of the
segments. These glands are formed of small tubes which come together
to form a small reservoir from which a single tube extends. This tube
meets its fellow and together as one tube they open to the exterior in a
small pore. Henseval, 1895-6, did not find the three pairs in all of the

270 Annals Entomological Society of America [Vol. XV,

forms studied but found a compound gland in the prothorax. This is
the condition of L. indivisus and P. inter r up ta, although the structure
of the two glands is not the same. In P. interrupta it resembles the glands
found by Gilson in P. grandis and is much branched, Plate XVIII,
Fig. 9, and Plate XIV, Fig. 2, ggl. The gland in L. indivisus is single
and lies above the prothoracic ganglion, its opening is between the
connectives of this ganglion to the sub-cesophageal and connects with a
spinneret which lies at the extreme anterior margin of the prothorax
and extends forward under the head, Plate XV, Fig. 1, at ggl, Plate
XVIII, Fig. 1, ggl, and Fig. 10. In H, analis a gland, corresponding
to this gland of Gilson, has not been found.

Glands in the Head of Limnophilus indivisus Walker.

In the head are six pairs of glands exclusive of the silk glands.
Lucas, 1893, Henseval, 1895, and Russ, 1907, mention two pairs and
term them mandibular and maxillary glands. L. indivisus possesses
these two pairs and others. The mandibular gland is situated on the
outer angle of the mandibular sclerite and is composed of a number of
single celled glands or " pockets" which open into a common duct.
This common duct leads to the base of the sclerite, the name of which
it bears, Plate XVIII, Fig. 14. The maxillary gland, as Lucas so terms
the second of the head glands, is similar to the mandibular but is com-
posed of many more of the small single celled glands. The two glands
lie underneath the oesophagus with their several small lobes folded
upon each other and their ducts extending almost at right angles from
each other. These ducts open into the buccal cavity at the inner margin
of the mandibular sclerite, Plate XVIII, Fig. 13. Patten, 1884, states
that they are an invagination of the inner margin of the mandibular
sclerite in the embryo and Patten terms them salivary glands. Further
ventrad in the lead lies a multicellular gland in the maxillary sclerite
with an opening into the distal end of this sclerite, Plate XVII, Fig. 12.
In the labium we find a pair of similar glands, Plate XVIII, Fig. 1 1 . With
these glands hitherto undescribed, and which we must, from their position
at least, term maxillary and labial glands, the so-called maxillary glands
of Lucas present a problem for nomenclature. Lucas ventures the
theory that the glands of the head are coxal glands and the homologs of
the parapodal glands of the annelid. If this theory be accepted then
the maxillary sclerites may not be possessed of two pairs of glands nor
may the mandibular sclerites. The writer prefers to use Patten's name
of salivary- gland, for the maxillary gland of Lucas.

Glands also exist at the base of the antennas and below the visual
area, but these are not figured.

Circulatory system of L. indivisus: This is simple as in all insects
and consists of the dorsal vessel which extends from the ninth segment
of the abdomen to the head, where it spreads out upon the supra-
cesophageal ganglia. There are nine pairs of alary muscles beginning
between the metathoracic and first abdominal segments and continuing
to lie between the segments as far back as between the eighth and ninth.
The first four are slender but the remaining five are heavy and connect
with the one in front and behind it. In front of each pair of muscles, a
valve exists in the dorsal vessel, Plate XIV, Fig. 8.

1922] Branch: Internal Anatomy of Trichoptera 271

BIBLIOGRAPHY.

Betten, Cornelius. 1901. Aquatic Insects in the Adirondacks, N. Y. State Museum

Bull. No. 47.
The Larva of the Caddis-fly, Molanna cinerea Hagen Jr. N. Y. Ento. Soc.,

Vol. X, pp. 147.
Binet, Alfred. 1894. Contribution a 1'etude du system nerveux sous-intestinal des

insectes. Journ. 1'Anat. et Physiol., XXX, 449-580.
Blanchard E. De la circulation dans les insectes. 1848. Ann. So. Nat. Zool. 3 ser.

T. IX.

Du system nerveux des insect:.. Ann. Sc. Nat. Zool. 3 ser. T. V., pp. 273-379.
Brauer, A. 1909. Die Siisswasserfauna Deutchlands Heft % Trichoptera beard.

v. G. Ulmer.
Bruntz, L. 1904. Contribution a 1'etude de 1'excretion chez les Arthropodes Archive

de Biologic, Vol. XX, pp. 335.
Chun, C. 1876. Uber den Bau die Entwickelung und physiologische Bedeutung der

Rectaldrusen bie den Insecten. Naturfcrschenden Gesellsschaft, Zehnte

Band.

Clark, Cora H. 1891. Caddice Worms of Stony Brook. Pysche 1891, p. 153.
Comstock, J. H. 1919. Introduction to Entomology.
Cottie, J. Th. 1881. Beitrage zur Kenntnis des Chorda supra-spinal der Lepidoptera

und des central, peripherischen und sympathischen nervensystems der

Raupen. Zeitschr. fur wissensch. Zool., 1881, Bd. 35, pp. 304-320.
Cummings, Bruce F. 1914. Scent Organs in Trichoptera. Proc. Zool. Soc. London,

1914, p. 459.
Dufour, M. Leon. 1847. Description et Anatomic d'une larve a branchies externes

d'Hydropsyche. Ann. Sc. Nat. Zool., ser 3, Vol. VIII, p. 341.
Dujardin, Felix. 1850. Memorie sur le systeme nerveux des insectes. Ann. Sc. Nat.

Zool., ser 3, Vol. XIV, pp. 195-206.
Faivre, E. 1857. Du cerveau des Dytisques considere dans ses rapports avec la

locomotion. Ann. Sc. Nat. Zool. ser 4, T 8.

Fernald, C. H. 1890. Rectal glands in Coleoptera. Am. Nat., Vol. 24, 1890, p. 100.
Gee, Wilson P. 1911. The Oenocytes of Platyphylax designatus Walker, Biol. Bui.,

Vol. 21, 1911, pp. 222-234."
Gilson, Gustave. Recherches sur les cellules secretant. LaSoie et les appareil

Sericigens. (1) Lepidoptera La Cellule VI, 1890. (2) Trichoptera La Cellule

X, 1894.
On the segmentally disposed Thoracic Glands in the larva of Trichoptera.

Jr. Linn. Soc. London. Zool., Vol. 25, No. 164, pp. 407, 1896.
Hammar, A. G. 1908. On the Nervous System of the Larva of Corydalis cornutus.

Ann. Ento. Soc. Amer., Vol. 1, No. 2.
Headlee, Thos. J. 1906. Blood Gills of Simulium pictipes. Am. Nat., Vol. 40,

pp. 875.

Henneguy, L. 1904. Les Insectes, p. 463.
Henseval, Maurice. Etude comparee des Glands de Gilson, La Cellule XI, 1895-6.

Les glands buccales des larva de Trichoptera. La Cellule XII, 1897.
Janet, Charles. 1898. Etudes sur les Fourmis, les Guepes et les Abeilles, Note 17.
Kellogg, Vernon, 1905. American Insects.

Kenyon, F. C. 1896. The Meaning and Structure of the socalled "Mushroom Bod-
ies" of the Hexapod Brain. Am. Nat. Vol. 30, p. 643.
Klapalek, Fr. 1888. Metamorphoses der Trichoptera, Serie I. Arch. Landesdf.

Bohmen. Bd. VI, No. 5.

Kolbe, H. J. 1893. Einfuhrung in die Kenntnis der Insekten.
Krauss, W. C. 1884. Nervous System in the Head of Corydalis cornutus Linn.

Psyche Vol. 4, p. 179.

272 Annals Entomological Society of America [Vol. XV,

Lucas, R. 1893. Beitrage zur Kenntnis der Mundwerkzeuge der Trichopteren.

Arch. f. Naturg. LIX, p. 285.
Lubben, Heinrich. 1907. Uber die innere Metamorphose der Trichopteren Zool.

Jahrb. Abt. Anat. Bd. 24, pp. 71-128.
Marchal, Paul. 1892. Sur la motilite des tubes de Malpighi. Ann. Soc. Ento. Fr.

T 61 Bulletin, p. CCLVI.
Marshall, Wm. S. The Early History of the cellular Elements of the Ovary of a

Phryganid, Platyphylax designatus Walker. Zeitschr-wiss. Zool. Bd. 86,

pp. 217, 1907.
On the Anatomy of the Dragon fly. Wisconsin Academy, Transactions 17,

1914.

Martynow, Von Andreas, 1901. Uber einige eigenthumliche Driisen bei den Trichop-
teren larven. Zool. Anz. XXIV, No. 649, pp. 449.
Miall and Hammond. 1900. The Structure and Life History of the Harlequin fly.

pp. 83.

Miall, L. C. 1905. Natural History of Aquatic Insects, Trichoptera, pp. 236.
Mlttler, Fritz. 1888. Larvae von Miicken und Haarfluglern mit zweierlei abwech-

selnd thatigen Athemwerkzeugen. Entomologische Nachrichten, Vol. 14,

No. 18; p. 273.
Needham, MacGillivray, Johannsen, Davis. 1903. Aquatic Insects in New York

State Mus. Bull. 68, Ento. 18.
Needham, J. G. 1897. Digestive Epithelium of Dragon fly Nymphs. Zool. Bull.,

Vol. 1, No. 2.
Noyes, Alice. The Proventriculus of an Hydropsyche Larva. Jr. Ento. & Zool.,

Vol. 7, 1915.
Netspinning Insects of Cascadilla Creek. Ann. Ento. Soc. Amer., Vol. VII,

No. 4, 1914.
The Ecology of the Hydropschidae and Philopotamidae of Rapid Streams

(unpublished paper).

Packard, Alpheus S. 1898. A Text-book of Entomology.
Palmen, J. A. 1877. Zur Morphologic des Tracheensystems.

Patten, Wm. 1884. Development of Phryganids. Quat. Jr. of Micro. Soc., XXIV.
Pictet, Francois Jules. 1834. Recherches pour servir a 1'historie et 1'anatomie des

Phryganides.

Rambur, M. P. 1842. Histoire Naturelle des Insectes, Neuropteres.
Russ, E. L. Postembryonale Entwicklung des Darmkanals bei den Trichopteren.

Zool. Jahrb. Abt. Anat. Bd. 25, pp. 675, 1907.
Beitrage zur Kenntnis der Kopfdriisen der Trichopteren larven. Arch. Zocl.

Exp. 5 ser. T 5, 1910, N. R. LXI.

Schroder, C. 1912-13. Handbuch der Entomologie, Vol. I.
Siltala, A. J. 1907. Uber die Nahrung der Trichoptera Acta. Soc. Fauna Flora

fennica Bd. 29, No.5.
Thienman, von A. 1903. Analkiemen bei den Larven von Glossosoma bolteni

Curt, und einigen Hydropsychen. Zool. Anz. Bd. XXVII, Nr. 4. .
Tutt, J. W. 1896. The Relationship of the lower Lepidoptera with Trichoptera.

Entom. Rec. Journ. Var., Vol. 8, pp. 25-29.
Van Gehuchten, A. 1890. Recherches histologiques sur 1'appareil digestif de la

larva de la Ptychoptera contaminata. La Cellule T VI, p. 185.
Vorhies C. T. The Development of the Nuclei of the Spinning Gland cells of

Platyphylax designatus Walker. Biol. Bull., Vol. 15, pp. 54-61, 1908.
Habits and Anatomy of the Larva of the Caddis fly Platyphylax designatus

Walker. Trans. Wis. Acad. So., Vol. XV, 1905.
Zander Enoch. 1901. Beitrage z ; ;r Morphologic des Mannlichen Geschlechtsan-

hange der Trichopteren. Zeitschr-wiss Zool., Bd. 70, p. 192.

1922] Branch: Internal Anatomy of Trichoptera 273

EXPLANATION OF PLATES.

PLATE XIV.

Fig. 1. Central nervous system of Limnophilus indivisus and larval reproductive

organs.
Fig. 2. Central nervous system of Phryganea interrnpta and larval reproductive

organs gdl=gonad from the ental lateral aspect. gd2 = gonad

frequently found and assumed to be the ovarian gonad.
Fig. 3. Central nervous system of Hydropsychodes analis and anal region with

blood gills protruding from anus.

Fig. 4. Dorsal aspect of the supracesophageal ganglia of Limnophilus indivisus.
Fig. 5. Lateral aspect of the supracesophageal and subcesophageal ganglia of

Limnophilus indivisus.

Fig. 6. Ventral aspect of subcesophageal ganglion of Limnophilus indivisus.

Fig. 7. Transverse section through the ovary of H. analis.

Fig. 8. Ventral aspect of the circulatory system of L. indivisus.

PLATE XV.

Fig. 1. Lateral aspect of the alimentary canal of Limnophilus indivisus.
Fig. 2. Oesophageal valve of Limnophilus indivisus. The portion of the canal

containing the valve has been slit longitudinally and the valve laid

open.

Fig. 3. A transverse cut back of the oesophageal valve.
Fig. 4. Diagram to show the relative position of the Malpighian tubules at the

division between mesenteron and hind intestine.

Fig. 5. Transverse cut through the rectal valve at a level with 5 in Fig. 1.
Fig. 6. Lateral section through the oesophageal valve. The cephalic end of the

valve is toward the bottom of the page.

Fig. 7. Lateral aspect of the alimentary canal of Hydropsychodes analis.
Fig. 8. Caudal aspect of anus of Hydropsychodes analis.
Fig. 9. Dorsal aspect of the anus of Hydropsychodes analis.
Fig. 10. Longitudinal section through the division point between mesenteron

and hind intestine showing a valve, caudad of the Malpighian tubules;

and the folded digestive epithelium of the mesenteron.
Fig. 11. Ventral aspect of the alimentary canal of Phryganea interrupta, only the

ventral pair of tubules are figured.

PLATE XVI.

Fig. A. Diagram of the hind intestine of Hydropsychodes analis, with the levels at

which the figures 1-6 are taken, indicated.
Fig. 1. Cross-section through the hind intestine at a point where a semi-rectal

valve is formed by the invaginated folds of the intestinal wall.
Fig. 2. Cross section taken at level No. 2, showing the glandular structure of

the large intestine.
Fig. 3. Cross section at level Xo. 3, showing the six folds of the small intestine

with the cubical cell in the wall and the ental layer of circular

muscles with the six pairs of longitudinal muscles.
Fig. 4. Cross section at level No. 4. showing the ectal row of circular muscles

in addition to the condition in Fig. 3.
Fig. 5. Cross section at level No. 5, showing the beginning of the columnar

epithelial cells and the breaking up of the six pairs of longitudinal

muscles into a layer of smaller longitudinal muscles.

274 Annals Entomological Society of America [Vol. XV,

Fig. 6. Cross section at level No. 6, showing the Malpighian tubules forming
in the hind intestine; also the breaking up of the ectal circular muscles.
Note the presence of intima which indicates the structure as being a
part of the hind intestine.

Fig. 7. A cross section slightly cephalad of the level of Fig. 6, showing the
digestive epithelium in diagram and the heavy layer of longitudinal
muscles characteristic of the mesenteron. The ventral pair of
Malpighian tubules are seen here just coming to the surface.

Fig. 8. A portion of a cross section of the mesenteron of Limnophilus indivisus,
which shows the normal two row r s of muscles.

PLATE XVII.

Blood Gills of Hydropsy chodes analis.

Fig. 1. Cross section of anal region to show the T-shaped anus. X 70.
Fig. 2. Cross section through the anus with a gill lying in the aperture. X 70.
Fig. 3. Cross section through the rectum showing all four gills. X 70.
Fig. 4. Cross section through the "so-called rectal valve." X 140.
Fig. 5. Sagittal section of the gill region showing the intestinal wall invagina-
tions that make the valve as at Fig. 4, and later make the gill wall
itself and are continuous with the rectal wall caudad of the gills.
Fig. 6. Sagittal section of the gill region to show the retractile muscle of the

gill and the relation to the body wall.
Fig. 7. Sagittal section of the gill region with the blood gills extended in

function. X 125.

Cross section of a functioning gill showing the three muscle branches.
The blood which fills the gills when in function. X 320.

PLATE XVIII.

Fig. 1. Dorsal view of the silk glands and Gilson's gland of L. indivisus.
Fig. 2. Ventral view of the mouth parts of L. indivisus with the silk glands

located.

Fig. 3. Lateral aspect of the mouth parts of L. indivisus.
Fig. 4. Dorsal aspect of the silk glands in relation to the suboesophageal

ganglion.

Fig. 5. Lateral aspect of a portion of the silk gland.
Fig. 6. Cross section of the gland proper of the silk gland of H. analis.
Fig. 6a. Cross section of the gland proper of the silk gland of L. indivisus.
Fig. 7. Longitudinal section of a Malpighian tubule.
Fig. 8. Cross section of a Malpighian tubule.

Fig. 9. Dorsal aspect of the Gilson's gland of P. inter rupta in relation to the
prothoracic ganglion.

Fig. 10. Dorsal aspect of the Gilson's gland of L. indivisus in relation to the

prothoracic ganglion.

Fig. 11. Ventral aspect of the glands in the labial sclerite of L. indivisus. X 120.
Fig. 12. Ventral aspect of the gland in a maxillary sclerite of L. indivisus. X 120.
Fig. 13. Ventral aspect of the maxillary gland of Henseval and Lucas. X 30.
Fig. 14. Ventral aspect of the mandibular gland. X 30.
Fig. 15. Cross section of several of the unicellular portions of the maxillarv eland

of Henseval and Lucas. X 30.

1922J

Branch: Internal Anatomy of Trichoptera

275

INDEX TO FIGURES.

a = anus.

abg = abdominal ganglia 1 to 8.

abs = abdominal segment 1 to 9.

ant = antennal nerve.

af = alary muscle 1 to 9.

b= nerve to front .of head.

bc = buccal cavity.

bg = blood gills.

bm = basement membrane.

c = crura cerebri.

cr = crop.

cm = circular muscles.

cp = corpuscle.

ct = conducting tubule.

dep = digestive epithelium.

dh = drag hooks.

dv= dorsal vessel.

ep = epithelium.

ex = expansion area.

excm = exterior circular muscle.

fa=frontal arm.

fg= frontal ganglion.

gd = gonad.

gdl=gonad in inner aspect.

gd2 = probable ovary of P. interrupta.

ggl = Gilson's gland.

glep= glandular epithelium.

gsp = spinneret of Gilson's gland.

in = intima.

1 = Lumen.

Itrl = labral nerve.

Ib2 = labral nerve.

lb-s = labral sclerite.

111 = labial nerve.

112 = labial nerve.
li-s = labial sclerite.
l-int = large intestine.
1m = longitudinal muscle.
md2 = mandibular nerve.

md-s = mandibular sclerite.

me = mesenteron.

mp = Malpighian tubule.

mpl = dorso-lateral pair.

mp2 = lateral pair.

mp3 = ventral pair.

ms = mesothorax.

mstg = mesothoracic ganglion.

mt=metathorax.

mttg = metathoracic ganglion.

n = nucleus.

oe = oesophagus.

og = opening of gland.

opt = optic nerve.

oev = oesophageal valve.

or=oesophageal ring.

p = pigment.

pm = gills press muscles.

pr = proventriculus.

pro = prothorax.

protg = prothoracic ganglion.

ptm = perotrophic membrane.

r = rectum.

rm = retractile muscle.

rn = recurrent nerve.

rv = rectal valve.

rw = rectal wall.

s = sympathetic ganglion.

sb-oeg = sub-oesophageal ganglion.

spr-oeg = supra-oesophageal ganglion.

skc = silk gland duct.

skp = silk gland proper.

sb = striated border.

sm-int = small intestine.

sp = spinneret.

t = tubule.

tr = trachea.

y = ventral end ot ovary.

ANNALS E. S. A.

VOL. XV, PLATE XIV.

HEB.

Hazel Elisabeth Branch.

ANNALS E. S. A.

VOL. XV, PLATE XV.

Hazel Elisabeth Branch.

ANNALS E. S. A.

VOL. XV, PLATK X\\.

mp 3

Hazel Elisabeth Branch.

H. E. B.

ANNALS E. S. A.

VOL. XV, PLATE XVII.

H. E. B.

Hazel Elisabeth Branch.

ANNALS E. S. A.

VOL. XV, PLATE XVIII.

H.EB.

Hazel Elisabeth Branch.

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WILL BE ASSESSED FOR FAILURE TO RETURN
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PAT. JAN 21, 1903

507/55

BJOLOY
LIBRARY

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