Chapter XXIV: Part I: Morphology and Physiology (20)

FIG. 427.—The lateral and lower series of sacs of _Bombus terrestris_,
♂: _a_, _c_, longitudinal tracheæ;, connected by _b_, and dilated at
_f_, and again in the succeeding segments; _i_, _k_, funnel-shaped
dilatations passing over the dorsal surface of the abdomen and
anastomosing (_g_) with their fellows opposite; at _l_,
communicating directly by a large branch.—After Newport.
]

There are two chief morphological tracheal systems: 1. The open or normal and primitive (_holopneustic_) type, and 2. The closed, or secondary and adaptive, _i.e._ _apneustic_, type. The open system is characterized by the presence of the stigmata. Through them the air directly enters into the tracheal tubes, whose delicate walls allow the exchange of gases in the blood. This type occurs in all sexually mature individuals, and also in the greater number of larvæ.

The closed or apneustic tracheal system is distinguished either by the want of stigmata, or, if present, they are not open, and do not function, so that the tracheæ cannot communicate with the air. In such cases the direct oxygenation of the blood is effected through the delicate integument, especially over the surface of the body in general, or in certain specialized places where the gill-like expansions of the skin are rich in tracheæ; such outgrowths, generally tubular or leaf-like, are called by Palmén _tracheal gills_.

This closed form of the tracheal system only occurs in the larval stage of aquatic or parasitic insects, as in the Plectoptera (Ephemeridæ), Perlidæ, Odonata, and Trichoptera, besides single genera of other orders, _i.e._ among Coleoptera, Gyrinus, Pelobius, Cnemidotus, and the young larva of Elmis; in the aquatic caterpillar of Paraponyx; in certain Diptera (Corethra, Chironomus, etc.), and some of the parasitic Hymenoptera (Microgaster).

Palmén has discovered that in the nymphs of Ephemeridæ, Perlidæ, Odonata, and the larvæ of most Trichoptera the tracheal branch (stigmatal branch) sent from the longitudinal trachea to where the thoracic stigmata would be situated if present, or where their vestiges only exist, are aborted, becoming simple solid cords not filled with air (Fig. 436, _vf_, and 447, _f_, funiculus or stigmatic cord). In the imago, however, they resume their function, connecting with the open functional stigmata. In Corethra, in its earliest stages, the entire tracheal system is, like the stigmatic branch, a system of solid cords and empty of air. (Palmén.)

Embryology shows that these stigmatal branches are well developed,
and are formed at the same time as the stigmata. It was also shown
by Dewitz, in a posthumous paper (1890), that in the young larval
stage of the Odonata and Ephemeridæ the tracheal system is at first
an open one, and in some of the families (Libellulidæ, Agrionidæ,
and Ephemeridæ) thoracic stigmata are seen at a very early stage.
From numerous experiments Dewitz concludes that in the young stages
of Odonata and Ephemeridæ there is an open tracheal system;
certainly in very young nymphs the thoracic spiracles allow the air
to pass out. Fully grown nymphs of Æschnidæ, Libellulidæ, and
Agrionidæ are capable not only of forcing the air out, but also,
like the perfect insect, of inhaling it. Moreover, he proved that
the gills of Ephemeridæ and Agrionidæ are not indispensable for the
maintenance of life, as the insects can live without them, breathing
either through the skin or by the rectum, or in both ways. It would
seem that while in freshly hatched or very young larvæ of aquatic
insects of different orders the skin is so delicate as to allow of
dermal respiration, in after life, when the skin becomes thicker and
denser, these expansions (gills), provided with a very thin and
delicate skin, of a necessity grow out from the walls of the body.

It thus appears that the closure and total or partial abolition of
the stigmata are in adaptation to aquatic life, and that such
insects have descended from terrestrial air-breathing winged forms.
This is an important argument against the view that the wings are
modified tracheal gills.

In this connection may be noticed the closure of the 2d and 3d
thoracic stigmata in holopneustic insects. We have found on laying
open the body of a Sphinx larva that a large number of tracheal
branches are seen to arise from the prothoracic and from the first
pair of abdominal stigmata. Now between these points there are no
spiracles or any external signs of them, there being in Lepidoptera
no mesothoracic or metathoracic spiracles. Yet the main lateral
trachea between the prothoracic and first abdominal segments
deviates from its course and bends down to send off a small
shrivelled stigmatal branch or cord to a place where, did a spiracle
exist, we should look for it. In the larva of _Platysamia cecropia_,
a similar vestigial stigmata branch is present.

In the larva of Corydalus, also, a trachea as large as the main
longitudinal one takes its origin and passes directly under the main
trachea. Now both tracheæ send a stigmatal branch opposite to where
the mesothoracic stigma should be, if present, _i.e._ on the hind
edge of the segment.

Verson, moreover, has found in the freshly hatched silkworm vestiges
of meso- and metathoracic stigmata, each consisting of a circle of
high hypodermal cells radially arranged around a common centre. The
stigmatal branch is long, but shrivelled; its peritoneum is widened
out into several berry-like saccules filled with cell-elements. In
profile these rudimentary stigmata appear as a series of high
hypodermal cells, which form the basis of a short blind tube.

Lydia M. Hart _del._

PLATE I.—Examples of metapneustic insects: 1, _Bittacomorpha
clavipes_, larva; 1 _a_, false foot; 1 _b_, its pupa; 2,
_Limnophila luteipennis_; 2 _a_, end of larva; 2 _b_, its pupa; 3,
end of larva of _Tipula eluta_.—After C. A. Hart.
]

After the second moult there begins a peculiar transformation of the
rudimentary stigmata. The stigmatal branch connected with them sends
off at various points thick tufts of capillary tracheæ which press
against the base of the blind tube. Gradually lengthening, they form
a fold which continues to increase in length. The numerous tufts of
tracheal capillaries extend beyond the inner surface of the two
layers of which the developing wing consists, the berry-like
saccules are drawn into the wing and converted into more or less
thick tubes, which finally form the “veins.” It is clear, therefore,
says Verson, as Landois claimed, that the wings of Lepidoptera must
be regarded as in the fullest sense organs of respiration. (Zool.
Anz., 1890, p. 116.)

The number of pairs of stigmata varies, especially in maggots or larval Diptera, in adaptation to their varied modes of life. The larvæ of most flies (Muscidæ) have a pair of peculiarly shaped processes on the prothoracic segment bearing spiracular openings, and two anal spiracles, while in _Ctenophora atrata_ L. only the anal pair are present. In the rat-tailed maggots (Eristalis) the long caudal process ends in two stigmata forming a respiratory tube, which can be thrust out of the water for the reception of air. In the larval mosquito (Fig. 433) and its ally, Mochlonyx, a short thick dorsal tube arises from the penultimate segment of the body, in which the two main tracheæ end, opening outward by a single spiracular aperture. Other dipterous larvæ (Simulium, Tanypus, and Ceratopogon) possess no spiracles, the tracheal system being a closed one.

The larvæ of most water beetles (Dyticidæ, Hydrophilidæ) possess but two spiracles, which, as in maggots, are situated at the end of the body. The aquatic larva of Amphizoa, according to Hubbard, breathes much as in the Dyticidæ, by means of two large valvular spiracles placed close together at the end of the body; “closed or rudimentary stigmata also occur on the mesothorax and on abdominal segments one to seven inclusive.”

Hubbard adds: “The larva of Pelobius is wholly aquatic and breathes
by branchiæ, but the obsolete stigmata are indicated precisely as in
Amphizoa, with the exception of the last pair, which in Amphizoa are
open spiracles, but in Pelobius are suppressed; the terminal eight
segments being prolonged in a swimming stylet.”

From a review of the distribution of spiracles, and their atrophy, partial or total, it will be seen that there are intermediate stages between the open (holopneustic) and closed (apneustic) systems. These, following Schiner, Brauer, and Palmén, may be defined thus:

1. _Metapneustic type._—The larvæ possess only a single pair of open
stigmata situated at the end of the body. (The dipterous Eristalis,
Tipula, Culex, Ptychoptera, Bittacomorpha (Plate I.) with certain
Tachinidæ, and in Coleoptera, the larvæ of Dyticus, and allies of
Hydrophilus and Cyphon.)

2. _Propneustic type._—The pupæ of Corethra, Culex, etc., in which
only the most anterior pair of spiracles are open.

FIG. 428.—Visceral tracheal system of the nymph of _Æschna
maculatissima_: _o_, œsophagus; _E_, stomach; _M_, urinary tubes;
_R_, rectum; _A_, anus; _tv_, visceral tracheal trunks; _td_,
dorsal trunks.—After Oustalet.
]

3. _Amphipneustic type._—Larvæ with a pair of open spiracles
situated at each end of the body, the intermediate spiracles being
closed. (Most dipterous larvæ, Musca, after the first moult,
Œstridæ, Asilidæ, and Syrphus.)

FIG. 429.—Branchial tuft of nymph of Æschna.
]

4. _Peripneustic type_; with prothoracic and abdominal spiracles,
the mesothoracic pair atrophied or closed. (The larvæ of Neuroptera,
Mecoptera, Trichoptera, Lepidoptera, of most Coleoptera,[72] of most
Diptera, and of most of the Hymenoptera.[73])

FIG. 430.—Part of three rows of respiratory folds from cuticular
living rectum of Æschna. The shaded parts are abundantly supplied
with tracheal tubes. The leaflets appear to be connected with a
central trachea, but this is not really the case.—After Miall.
]

These differences in the number of functional spiracles are in
direct relation with the surroundings of the insects, the physical
conditions of existence evidently determining the position of the
active functional open spiracles and the closure of those useless to
the organism.

_i._ The rectal tracheal gills, and rectal respiration of larval Odonata
and other insects

The remarkable mode of respiration by tracheal gills situated within the intestine of the nymphs of dragon-flies was first described by Swammerdam and afterwards by Réaumur. The most complete and best illustrated modern account is that of Oustalet. In these insects the large rectum is lined with six double longitudinal ridges, in Æschna bearing numerous delicate tubes or papillæ, each of which contains very numerous (by estimate 24,000) tracheal branches (Fig. 431); while in Libellula the gills are lamellate (Fig. 432). The tracheæ arise both from the main dorsal and visceral longitudinal trunks, which give rise to secondary branches passing into the walls of the rectum and sending into the branchial papillæ fine twigs, which, extending to the distal end of the papilla or lamella, recurve and anastomose with the efferent twigs.

FIG. 431.—A small part of one leaflet, highly magnified, showing many
fine tracheal branches. The portion shown is marked by a small
circle in Fig. 430, lower left-hand corner.—After Miall.
]

FIG. 432.—Leaves, _mh_, from a lamellate tracheal gill of Libellula:
_t_, trachea.—This and Fig. 429, after Oustalet.
]

The anal opening is externally protected by the suranal and lateral triangular chitinous plates, three to five in all. When open, the water passes into the rectum and bathes the rectal gills, where it may be forcibly expelled as if shot out from a syringe, thus propelling the insect forward. In Libellula the anus affords direct access to the intestinal cavity, but in Æschna Oustalet describes “a sort of vestibule separated from the rectum by a circular valvule.” He also states that the inspiration and the repulsion of water is produced at irregular intervals, and rather by the movements of the dorsal and sternal arches of the abdomen than by the contractions of the rectum, since the walls of this organ are less muscular than is supposed.

FIG. 433.—Larva of a mosquito (_Culex nemorosus_) of middle age, seen
from above, the tracheal system omitted: _at_, antennæ; _ab_, their
middle joint; _eg_, elastic articular membrane; _atm_, antennal
muscle; _atn_, antennal nerve; _zau_, compound; _eau_, simple eye;
_os_, brain; _oex_, extensor; _ofl_, flexor of labrum; _ha_, neck;
_œ_, œsophagus; _spd_, salivary gland; _mau_, cœca; _ch_, chyle
stomach; _di_, contents of intestine; _mg_, urinary tubes; _dd_,
ileum; _ed_, rectum; _a_, anus; _s_, sipho; _z″_, its bristles;
_kb_, tracheal gills: _k_{1}_, _k_{2}_, _k_{3}_, closing lobes of
the sipho; _kn_, basal tubercle of tactile hair; _g_, its ganglion
cell; _th_, tactile hair of the siphon valve.
]

The nymph of Calopteryx (and probably of all the group
Calopteryginæ) possesses rectal gills besides external caudal
tracheal gills. There are three double rectal longitudinal folds or
ridges, interpenetrated by tracheal twigs. (Dufour, denied by
Poletaiew, but confirmed by Hagen.)

Dewitz claims that the caudal gills of the Agrionidæ are not their
sole means of respiration, since he cut off the caudal tracheal
gills of an Agrionid nymph, which continued to live for a week.
Hence he thinks that there may be a rectal respiration, since under
the microscope he saw a stream of water pass in and out of the end
of the intestine.

Dewitz’ experiments prove that in young Ephemerids there may be
besides branchial, both rectal and skin respiration. He saw under
the microscope the anus for a while opened and then closed, causing
the rectum to move; powdered carmine mixed with water was drawn into
and then expelled from the rectum. There was, however, no
enlargement and contraction of the abdomen as in the rectal
respiration of Æschna. (Zool. Anz. 1890, p. 500.)

FIG. 434.—End of the body of the same larva as in Fig. 431, seen from
the side, the branches of the main tracheæ (_htr_) omitted: _kbl_,
excrementitial pellet in rectum; _kb_, tracheal gills; _b_, funnel
of the closing apparatus; _hz_, hollow tooth of the closing
apparatus; _k_{1}_, _k_{2}_, _k_{3}_, siphonal lobes; _th_, tactile
hair; _as_, chitinous plate; _str_, rudder; _l_, its thickened edge;
_sch_, its shank; _z′_, _z″_, bristles.—This and Fig. 433, after
Raschke.
]

Eaton states that there is a rectal respiration in the nymphs of may-flies, and Palmén observed in young larvæ of Bætis and Cloëon that the rectum took in “by gulps” water colored by carmine and expelled the whole of it at once, in order to fill it again in the same way. “This rectal respiration therefore corresponds to that of Libellulid larvæ.”

FIG. 435.—Thorax and anterior abdominal segments of the nymph of a
may-fly (_Cloëon dimidiatum_) with tracheal gills (_tk_{1}_,
_tk_{2}_, _tk_{3}_) and the rudiments of the fore wings (_VF_) and
hind wing (_HF_): _tl_, tracheal longitudinal trunks.—After Graber,
from Lang.
]

FIG. 436.—Gills on the middle abdominal segments of larva of _Bætis
binoculatus_: _trl_, longitudinal tracheal trunks; _vf_, stigmatic
cord; _ktr_, gill-tracheæ; _trk_, tracheal gills.—After Palmén, from
Lang.
]

Besides breathing by spiracles, by tracheal gills, as well as through the integument, the larva of Culex has been observed by Raschke to have a rectal respiration. At the anterior end of the rectum arises a countless number of fine tracheæ, which pass through the walls and, subdividing, end in numberless very fine twigs in the papilla-like folds situated within the rectum. The supply of tracheal twigs is greatest where the papillæ are largest. (Figs. 433, 434.)

_j._ Tracheal gills of the larvæ of insects

In many aquatic insects respiration is carried on by tracheal gills. These are delicate, hollow, leaf-like or tubular outgrowths of the integument usually attached to the sides or end of the hind-body, and containing a trachea which usually sends off numerous minute branches, so that the exchange of gases readily takes place in them.

FIG. 437.—A, nymph of _Ephemerella ignita_, with gills of left side
removed; _g_, gills. _B_, nymph of Tricorythrus (_sp_), with
gill-cover of right side removed; _gc_, gill-cover; _g_, _g′_,
gills.—After Vayssière.
]

FIG. 438.—Left maxilla of _Jolia weselii_, with the cephalic tracheal
gill (_h_) inserted at the base on the under side.—After Vayssière.
]

Palmén has shown that these tracheal gills, as he calls them, are not developed on the same segments as the stigmata, and that the two structures have no genetic connection with each other. It is evident that these gills are secondary, adaptive organs.

In some cases (see p. 475) the tracheæ are wanting, but as such gills are filled with blood, the air contained in the water must pass in through their delicate walls.

In the Plectoptera (Ephemeridæ) the tracheal gills are either foliaceous or filamentous; when foliaceous they form simple or double leaves, with or without branches, or with a fringe of tubules, or under the leaf-like cover-bearing tufts of filaments. They are situated on the (usually) basal seven abdominal segments, at their hinder edge (Figs. 435, 436). In Oligoneuria and Jolia a pair occurs on the under side of the head, attached to the maxillæ, while in Jolia there is a pair on the under side of the first thoracic segment at the insertion of each of the legs. In certain genera (Heptagenia, Oligoneuria, and Jolia), they are in the form of a flat cover, under which lies a tuft of respiratory tubes, or (Ephemerella) a small bifid cluster of very delicate leaves (Fig. 437, _A_). In Cœnis and Tricorythus the tracheal gills of the second pair are modified to form plates covering all the succeeding pairs, those of the first pair being nearly atrophied and well-nigh functionless. (Fig. 437, _B_.)

FIG. 439.—Inner side of a gill-cover of the first pair, of
Ephemerella, with the tracheal gills.—After Vayssière.
]

FIG. 440.—Nymph of Bætisca: III, section of abdomen; _a_, gills; _b_,
flap; 1–9, abdominal segments.—After Walsh.
]

FIG. 441.—Nymph of _Prosopistoma punctifrons_: _o_, upper orifice of
the respiratory chamber.—After Vayssière.
]

FIG. 442.—Filamentous tracheal gill and part of a trachea of
Pteronarcys.—After Newport from Sharp.
]

Finally, in the highly modified forms Bætisca and Prosopistoma the tracheal gills are entirely concealed and protected by mesothoracic projections so as to form a true respiratory chamber, to which the water has access either by an opening behind, as in Bætisca, or by three openings, two ventral and one dorsal (Fig. 441), as in Prosopistoma.

The slender cylindrical tracheal gills of Heptagenia in the third or fourth nymphal stage are 2–jointed, and the first abdominal pair in Cænis are said by Palmén to be finger-shaped and 2–jointed. In _Polymitarcys virgo_ the gills do not appear until the eighth or tenth day after hatching.

Dewitz found that young nymphs of Ephemerids will well endure the
amputation of their gills, while fully grown ones die. Amputation of
the lateral gills hastens ecdysis. After the change of skin, the
gills are smaller than before, and at first contain no tracheæ, but
in a few weeks they develop as completely as in normal individuals.
The caudal gills were also renewed.

FIG. 443.—_A_, larva of Sisyra, enlarged. _B_, one of the hinder
gills, with its tracheæ.—After Westwood, from Sharp. _C_, a gill,
showing the branched tracheæ.—After Grube.
]

In the nymphs of Perlidæ the tracheal gills are usually present, and are either foliaceous (Nemoura) or more commonly filamentous in shape (Fig. 442). They are situated either on the prosternum (Nemoura and Pteronarcys), or on each side of the thorax, or on the sides of the abdomen, or are restricted to a tuft on each side of the anus at the base of the caudal stylets (Pteronarcys and Perla). Unlike the Ephemeridæ the gills persist in certain genera throughout life.

The larvæ of the aquatic Neuroptera, Sisyra, Sialis, and Corydalus possess lateral pointed bristle-like tracheal gills, which in Sisyra are 2–jointed; those of Sialis are, in the living larva, curved upwards and backwards (Fig. 444). Corydalus is also provided with a ventral tuft of delicate filamentous gills, which, however, according to Riley, do not appear until after the first moult.

While the nymphs of Agrionidæ (which have rectal gills) respire chiefly by the large caudal foliaceous gills (Fig. 445), there are, according to Hagen, two genera of the Calopteryginæ (Euphæa, Fig. 445, and Anisopleura) whose nymphs possess seven pairs of external lateral tracheal gills, in shape like those of Sialis, besides three caudal and three rectal tracheal gills.[74]

FIG. 444.—Larva of _Sialis lutarius_.—After Miall.
]

FIG. 445.—Caudal tracheal gill of nymph of Agrion.
]

Hagen has also detected in the under side of the 5th abdominal
segment of Epitheca and Libellula a pair of sacs of the shape of a
Phrygian bonnet, each of which contains a smaller sac lined with
epithelium,—as in Æschna they occur in the 5th and 6th, and in
Gomphus in the 4th, 5th, and 6th segments. This serial arrangement
appears to confirm Hagen’s suggestion that they are survivals of
abdominal gills, which in Euphæa are completely evaginated.

FIG. 446.—Nymph of Euphæa, showing the lateral gills: _a_, one
enlarged.—Folsom _del._
]

In the Trichoptera, all of which, except Enoicyla, are apneustic, and most of which have tracheal gills, the latter are filamentous, and arise either from the dorsal and ventral sides of the abdominal segment, or they grow out from the sides; while in certain genera (Neuronia, Phryganea, etc.) the gills are represented by conical hooks on the sides of the 1st abdominal segment, which are evidently respiratory, as they contain numerous tracheæ. The tracheal gills are either single or more rarely form tufts (Figs. 447, 448).

In Hydropsyche (Fig. 448) the tracheal gills persist throughout life, while in other genera they only last through the pupal stage. When first hatched, the larva of Phryganea lacks gills. The larvæ of most of the Hydropsychidæ, Rhyacophilidæ, and Hydroptilidæ have no gills, though they appear well developed in the pupal stage. (Klapálek.)

FIG. 447.—_A_, an abdominal segment of Hydropsyche, with the tracheal
gills (_lbr_): _trl_, longitudinal tracheal trunk; _f_, stigmatal
branch. _B_, 5th abdominal segment of pupa of the same; _l_, the
three lateral flaps of the tergite; _br^1_, _br^2_, branchiæ.
]

FIG. 448.—Imago, abdominal segments IV to VI, with the gills at _a_
concealed in their natural condition; at _b_, drawn out with the
needle; at _c_, projecting abnormally and dried.—This and Fig. 447
after Palmén.
]

FIG. 449.—Larva and pupa of _Paraponyx stratiolata_, enlarged; _s_,
spiracle.—After De Geer (compare Hart’s figure of _P. obscularis_,
living in the Illinois River).
]

The only lepidopterous larva known to be provided with tracheal gills is that of the pyralid genus Paraponyx. Its thread-like gills, arranged in tufts of three or four, arise from a common tubercle situated on the sides of nearly all the segments. Wood-Mason describes the East Indian _P. oryzalis_ as “covered with a perfect forest of soft and delicate white filaments,” arranged in tufts disposed in four longitudinal rows. “The stigmata of the 2d, 3d, and 4th abdominal somites only are clearly discernible.” The caterpillar crawls “free and uncovered” over the submerged leaves of the rice plant “in the very midst of the water.” In a Brazilian species of Paraponyx described as _Cataclysta pyropalis_, by W. Müller, the tufts are reduced to simple unbranched filaments, and the case is more complex than in the European species (Fig. 449).

FIG. 450.—Anterior end of larva of _P. stratiolata_, showing the head
and first two thoracic segments, with their gills: _A_, a tuft of
gills, much enlarged.—After De Geer.
]

FIG. 451.—Larva (1) and pupa (2_a_) of _Paraponyx pyropalis_ enlarged:
_st_, stigmata.—After W. Müller.
]

Of coleopterous larvæ breathing by tracheal gills there are but few. The larva of Gyrinus (Fig. 454) respires by 10 pairs of slender, hairy abdominal gills similar to those of Corydalus, and the stigmata are entirely wanting. Somewhat similar are the tracheal gills of _Hydrocharis caraboides_. Hydrobius has shorter setose gills, our American species having seven pairs of short setose gills. It has two spiracles at the end of the body, through which the air is taken by thrusting the body out of the water. The larvæ of two other aquatic coleopterous genera, Pelobius and Cnemidotus, also have gills; those of the former situated at the base of the coxæ, and brush-like, but containing no tracheæ, though filled with blood, while those of Cnemidotus are very long, bristle-like, jointed, and arising from the dorsal side of the thoracic and abdominal segments. The stigmata are wanting. (Schiödte.)

The larva of the dipterous genus Tanypus respires by two caudal papilliform processes, in each of which a trachea ramifies.

FIG. 452.—Freshly hatched larva of Hydrobius: _t_, enlarged tracheæ,
the heart between them; _g^1_-_g^7_, the seven pairs of gills. _A_,
end of body, enlarged, showing the two terminal stigmata.—Emerton
_del._
]

Certain larvæ with both stigmata and tracheal gills are enabled either to live in or out of water or on the surface, as in the case of certain beetles (Cyphonidæ, Elmidæ, Hydrophilidæ, Fig. 452), or the larval mosquito and Psychodes (Fig. 455); also the nymphs of dragon-flies.

The larvæ of the Cyphonidæ (Helodes, Cyphon, Hydrocyphon) possess but a single pair of stigmata, situated in the penultimate abdominal segment, while at the end of the abdomen are delicate tracheal gills. The two main tracheal trunks are much swollen. When on the surface of the water the larva breathes through the stigmata situated near the end of the abdomen; when floating in the water, the larva, like that of Gyrinus, carries along at the end of its body a bubble of air. The gills are only of use, as Rolph thinks, when the insect is compelled to remain a long time under water.

The larva of our native _Prionocyphon discoideus_ (Say) is described by Walsh as “vibrating vigorously up and down a pencil of hairs proceeding from a horizontal slit in the tail”; this pencil is composed “of three pairs of filaments, each beautifully bipectinate. I presume it is used to extract air from the water.” When the larva is at the surface the pencil of hairs touches the surface of the water, and occasionally a bubble of air is discharged from the tail. “The general habit is to crawl on decayed wood beneath the surface, occasionally swimming to the surface, probably for a fresh supply of air.” (Proc. Ent. Soc. Phil., i, p. 117.)

FIG. 453.—Larva of Psephenus, enlarged.
]

FIG. 454.—Larva of Gyrinus.—After Westwood.
]

The larvæ of the small water beetles of the family Elmidæ (Elmis, Potamophilus, Macronychus, and Psephenus) have similar habits. That of Elmis has ten dorsally situated pairs of spiracles, and on the end of the body bushy gills which are protruded at pleasure. The young larva is without spiracles, its tracheal system being closed. Macronychus and Potamophilus have similar habits. In the larva of the latter genus, which has nine pairs of spiracles, there are at the end of the body on each side three tufts of thread-like gills which are connected with the two main horizontal tracheæ, while the branches of the abdominal tracheæ are dilated into numerous (64) bladder-like sacs. The larva usually breathes through the caudal gills. When the water is low or dried up, the air is inhaled directly through the spiracles. (Kolbe.)

The larva of _Psephenus lecontei_, by its broad hemispherical body, is adapted to adhere to the smooth surface of rounded stones, in which situation we have found it. Although it is said by Rolph to have two pairs of spiracles, one pair on the mesothoracic and the other on the 1st abdominal segment, it probably rarely rises to the surface to breathe the air direct.

FIG. 455.—End of body of a Psychodes larva: _A_, end of body of a
young, freshly moulted larva, side view: _a_, the three anal gills;
_b_, the left air-cavity. _B_, older larva of the same species, with
the open air-cavity seen from above. _C_, end of larva of another
species as it goes down into the water with a bubble of air, _b_,
between the crown of hairs of the air-cavity or tube: _a_, the two
pairs of anal gills; _b_, the two main tracheæ.—After F. Müller.
]

It possesses five pairs of gills on the under side of the 2d to the 6th abdominal segments. Each gill has finger-shaped processes on its hinder edge, which are “from their constant motion evidently connected with respiration.” Tracheæ may be seen, according to H. J. Clark, entering the gills, and “the circulation of water among the branchiæ is kept up by the flapping of the tail-pieces.” The larva of _Helichus fastigiatus_ is said by Leconte to be “very nearly allied, while the remotely allied _Stenelmis crenatus_ has no external branchiæ.”[75]

The larva of the mosquito also has two modes of respiration,
breathing either at the surface of the water through the two
spiracles situated on the projection (siphon) at the hinder end of
the body which is thrust out into the air; or when at the bottom
respiring by tracheal gills. The pupa also has a double mode of
respiration, either taking in air at the surface by the two thoracic
horns with stigmatic openings, or when submerged using its tracheal
gills.

Besides its long caudal tracheal air-tubes, the larval Eristalis is
said by Chun to thrust out from the anus a number (20) of short
tracheal filaments which float about in the water and serve to
absorb the air.

An aquatic Brazilian larva of the family Psychodidæ has been found by Fritz Müller to take down under the water a large bubble of air (Fig. 455, _C_), the main tracheal trunk ending each in an opening at the end of the body (_A_, _B_); besides this, while at the bottom it breathes by three digitiform tracheal gills; another species having two pairs (_C_, _a_).

FIG. 456.—Under side of body of larva of Blepharocera. showing the
position of the tracheal gills: _A_, section of the body through a
sucker, showing position of the gills. _B_, section of a sucker:
_br_, gill with numerous tracheæ; _gl_, outlet of excretory gland;
_M_, _m_, muscles.—After F. Müller.
]

The remarkable larvæ of the Blepharoceridæ (represented in the United States by _Blepharocera capitata_), which live permanently in swift streams, attached by median suckers to stones, are apneustic, and breathe solely by leaf-like tracheal gills (Fig. 456, _br_) attached to the under side of the second to sixth abdominal segments. Those of the European Liponeura are said by Wierzejski to be branched, tree-like. Also immediately in front of the anus and behind the last sucker are four membranous sacs provided with tracheæ, but which are not capable of being withdrawn. These are said by Müller to be the same as what Dewitz states to serve as gills, and by Wierzejski they are homologized with the four anal gills of Chironomus.

The double mode of respiration in the larva of the horse bot-fly has
been described by Scheiber. On the hinder end of the body are the
stigmatic plates, which contain two lateral gill-plates and the
middle stigmatal leaf. Besides this there is a pair of slightly
developed prothoracic spiracles. The embryo and also freshly hatched
larva of _Gastrophilus equi_ do not possess these gill-plates, but
on the end of the body are, according to Joli, two long thread-like
gills. The freshly hatched larva of the allied _Cephenomyia
rufibarbis_ bears two caudal projections. (Kolbe.) As in shrimps and
other Crustacea the gills are kept in constant motion, the water
being driven over them by the rapid movements of the telson, so in
the larval may-flies, and in the case-worm (Macronema), the gills
move more or less rapidly. In case-worms as well as larval Perlidæ,
Sialidæ, Paraponyx, and Hydrophilidæ the abdominal region is
constantly moved to promote respiration. (Kolbe.)

=Blood-gills.=—Fritz Müller describes in trichopterous larvæ certain delicate anal tubular processes into which the blood flows, and which do not as a rule contain tracheæ, though occasionally very fine tracheal branches. Müller compares them with the gills of crabs and of shrimps. They are eversible finger-like tubules. They are used when the tracheal gills are temporarily not available. Their number varies even in the same genus. There are six in certain Rhyacophilidæ; five in different Hydropsychidæ; in Macronema there are four, and they are green when filled with the green blood of that insect, the tracheal gills being whitish. In the freshly hatched larva, while the tracheal gills are present, no anal blood-gills are visible. Similar blood-gills also occur in the pupæ of certain caddis-flies. (Pictet.)

Similar anal gills filled with blood occur in the larvæ of the fireflies (Lampyris, etc.), and perhaps, Kolbe thinks, serve for respiration, though other authors believe them to be adhesive organs.

The larva of Pelobius has true blood-gills. (Schiödte. See p. 461.)

The eversible ventral segmental sacs of Scolopendrella, Campodea,
and Machilis, as well as the ventral tube (collophore) of Podura,
Smynthurus, etc., may, as Oudemans and Haase have suggested, serve a
respiratory purpose, though they lack tracheæ, and differ from
blood-gills in containing no gases; yet the blood is forced into
them, causing their eversion. Oudemans observed that Machilis
everted its sacs when the vessel in which it was put was filled with
warm, damp air. The sacs are only thrust out when the creature is
completely at rest.

Structures referable to blood-gills also occur temporarily in the embryo of Orthoptera; Rathke observed them in the mole-cricket; Ayres observed them in _Œcanthus niveus_, where they form two stalked broad oval appendages on the first abdominal appendages, which he regarded as gills. Patten observed them in _Phyllodromia germanica_, as pear-shaped structures occurring in the same situation, but regarded them as sense-organs, as did Cholodkowsky. Graber found these structures in the embryo of the May-beetle, which looked like the other embryonic limbs, but survived after the disappearance of the latter, being longer and broader and unjointed. These disappeared shortly before birth. In Hydrophilus they remain, Graber states, after birth. Nussbaum has seen them in Meloë.

Finally, Wheeler has discussed at length these embryonic organs, which he regards as glandular structures, and calls _pleuropodia_, their primitive function having been that of limbs. He has detected them in the embryo of _Periplaneta orientalis_, _Mantis carolina_, _Xiphidium ensiferum_ (Fig. 387); also in the Hemiptera (_Cicada septemdecim_, _Zaitha fluminea_), and in _Sialis infumata_. He discards the view that they were once gills or sense-organs, and concludes that they were glands. But, as we have suggested, their function once that of gills, and still respiratory in Synaptera, has perhaps become in the winged insects glandular and repugnatorial. Instead, then, of being modified abdominal limbs afterwards serving as glands, as Wheeler claims, we are inclined to believe that they functioned as blood-gills.

_k._ Tracheal gills of adult insects

Tracheal gills are known to be retained by a few insects in the imago stage, the nymphs in all stages breathing by them. The most notable example is the perlid genus Pteronarcys, in which, as Newport states, there are eight sets, comprising 13 pairs of branchial tufts distributed over the under surface of the thoracic and first two abdominal segments.

The first set, consisting of three pairs of tufts, partly encircling
the neck like a ruff, arises from the soft membrane connecting the
head and prosternum. The thoracic tufts originate between and behind
the coxæ, as well as on the front margin of the meso- and
metathoracic segments. The number of filaments in each tuft varies
from about 20 to 50 or more, the densest tufts being those of the
two hinder thoracic segments. Each filament is usually simple,
though in a few cases they are branched (Fig. 457, _A_).

The adult Pteronarcys is nocturnal, flying only at dewfall or in the
night, and Mr. Barnston observed it when on the wing, “constantly
dipping on the surface of the water”; by day it hides “in crevices
of rocks which are constantly wetted by the spray of falling water,
under stones and in other damp places.” It may thus be compared with
the Amphibians, Necturus and Proteus, whose gills are retained in
adult life. A similar large Chilian Perlid (_Diamphipnoa lichenalis_
Gerst.) differs in completely lacking the thoracic gills, though
there are four pairs on the abdomen, _i.e._ a pair on each of the
first four segments. In this form the number of individual filaments
in the largest tufts may amount to about 200.

Another Perlid (_Dictyopteryx signata_) is said by Hagen to have two
pairs of gill-tufts on the under side of the head; the first pair
situated on the base of the submentum, the second on the membrane
connecting the head and prosternum.

Kolbe states that in the imagines of _Perla marginata_ and _P.
cephalotes_ on the hinder edge of the thoracic stigmata arise three
very small chitinous plates, which, on their under side and on the
edges are beset with numerous short white filaments. These
completely correspond to the filaments of the tuft-like larval
gills. Persistent anal gills also occur in the imagines of Perla.

FIG. 457.—Under side of _Pteronarcys regalis_, showing the situation
of the gills _(g_, _b_, _f_) and the sternal orifices: _A_, a
branchial filament showing the direction of the current of blood;
_c_, _d_, tracheæ. _B_, end of the abdomen enlarged.—After
Newport.
]

In _Nemoura lateralis_ and _cinerea_ the tracheal gills are
differently disposed. On each side of the anterior edge of the
prosternum arise delicate tightly twisted filaments, like those of
the larva. (Einführung, p. 536.)

Hagen also states that in the dragon-fly, Euphæa, the gills of the
nymphs are retained in the imago, and Palmén remarks that in Æschna
the rectal gills of the nymph persist in the imago, though not used
for respiration.

Palmén gives an instance of a caddis-fly (Hydropsyche, Fig. 448)
retaining its gills through the imago stage, but they are unfit for
respiration, as they are minute and shrunken.

A walking-stick (_Prisopus flabelliformis_) found in the mountains
of Brazil has the remarkable habit, according to Murray, of spending
“the whole of the day under water, in a stream or rivulet, fixed
firmly to a stone in the rapid part of the stream,” with its head
turned up stream; but leaving the water at dark. The under side of
the body, including the head, is hollowed so that the creature may
adhere, sucker-like, to smooth stones; the claws, claspers, and
flaps on the legs aid in retaining its hold, while the outer margin
of the legs is dentate and thickly fringed with hair to repel the
water.

Another form, closely related to Prisopus, from Borneo (_Cotylosoma
dipneusticum_) is said by Wood-Mason to be even more profoundly
modified for an aquatic life, since it has not only spiracles, but
also, as he claims, tracheal gills. From each side of the body, in
fact along the lower margins of the sides of the metathorax, there
stand straight out five equal, small, but conspicuous ciliated oval
plates, “which, when the insect is submerged and its stigmata are
closed, doubtless serve for respiration.” The author did not note
the actual presence of tracheæ in these plates.

LITERATURE ON THE ORGANS AND PHYSIOLOGY OF RESPIRATION

_a._ On the tracheal system in general

=Lyonet, P.= Traité anatomique de la chenille qui ronge le bois du
saule. (La Haye, 1760; 2d edit., La Haye, 1762, pp. 616, 18 Pls.)

=Treviranus, G. R.= Beiträge zur Anatomie und Physiologie der Tiere
und Pflanzen, 1816.

—— Das organische Leben. Bremen, 1831.

=Rengger, J. R.= Physiologische Untersuchungen über die tierische
Haushaltung der Insekten. Tübingen, 1817. (Germar’s Mag. f. Ent.,
1818, iii, pp. 410–413.)

=Dufour, L.= Recherches anatomiques sur les Carabiques et sur
plusieurs autres insectes Coléoptères. Organes de la respiration.
(Ann. Sc. nat., viii, 1826, pp. 19–27, 2 Pls.)

—— Études anatomiques et physiologiques sur les insectes Diptères de
la famille des Pupipares. Appareil respiratoire. (Ann. Sc. nat.
Zool., Sér. 3, iii, 1845, pp. 56–64, 1 Pl.)

—— Description et anatomie d’une larve à branchies externes
d’Hydropsche. (Ann. Sc. nat, Zool., Sér 3, 1847, viii, pp. 341–354.)

—— Études anatomiques et physiologiques, et observations sur les
larves des Libellules. Appareil respiratoire. (Ann. Sc. nat. Zool.,
Sér. 3, xvii, 1852, pp. 76–97, 3 Pls.)

—— Recherches anatomiques sur les Hyménoptères de la famille des
Urocerates. Appareil respiratoire. (Ann. Sc. nat. Zool., Sér. 4, i,
1854, pp. 203–209, 1 Pl.; see also p. 344.)

=Burmeister, H.= Handbuch der Entomologie, i, 1832, pp. 169–194,
416–436.

=Kirby, W., and W. Spence.= Introduction to entomology, 1833, iv, pp.
35–81.

=Bowerbank, J. S.= Observations on the circulation of blood and the
distribution of the tracheæ in the wing of _Chrysopa perla_. (Ent.
Mag., iv, 1837, pp. 179–185.)

=Platner, E. A.= Mitteilungen über die Respirationsorgane in der Haut
bei der Seidenraupe. (Müller’s Archiv f. Physiol., 1844, pp. 38–49.)

=Filippi, F. de.= Alcuni osservazioni anatomico-fisiologische sugl’
Insetti in generale, ed in particulare sul Bombice del Gelso. (Ann.
R. Acad. d’ Agricoltura di Torino, 1850, ii, p. 25, 1 Pl.; Transl.
by C. A. Dohrn, Stettin, Ent. Zeit., 1852, xiii, pp. 258–267; xiv,
pp. 124–132, 1 Pl.)

=Newport, G.= On the formation and the use of the air-sacs and dilated
tracheæ in insects. (Trans. Linn. Soc. London, 1851, xx, pp.
419–423.)

=Lubbock, J.= Distribution of tracheæ in insects. (Trans. Linn. Soc.
London, 1860, xxiii, pp. 23–50.)

=Landois, L.= Anatomie des _Phthirius inguinalis_ Leach. (Zeitschr. f.
wissens. Zool., xiv, 1864, pp. 1–26, 5 Taf.)

—— Anatomie des _Pediculus vestimenti_ Nitzsch. (Ibid., xv, 1865, pp.
32–55, 3 Taf.)

—— Anatomie des Hundeflohs (_Pulex canis_). (Nova Acta Leop.-Carol.
Akad. der Naturf., Dresden, 1866, xxxiii, 1867, pp. 67, 7 Taf.)

—— Anatomie der Bettwanze (_Cimex lectularius_ L.). (Ibid., xviii,
1868, pp. 206–224, xix, 1869, pp. 206–233, 4 Taf.)

=Meinert, Fr.= Campodeæ: en familie af Thysanurernes orden.
(Naturhistorisk Tidsskr., 3 Raek., iii, 1864–65, pp. 400–440, 1 Pl.)

=Reinhardt, H.= Zur Entwicklungsgeschichte des Tracheensystems der
Hymenopteren mit besonderer Bezeichung auf dessen morphologische
Bedeutung. (Berlin. Ent. Zeitschr., 1865, ix, pp. 187–218, 2 Taf.)

=Gerstaecker, A.= Bronn’s Klassen und Ordnungen des Tierreichs, v,
1866–1879. Organs of respiration, pp. 119–131.

=Pouchet, G.= Développement du système trachéen de l’Anophèle
(_Corethra plumicornis_). (Archiv zool. expérimentale, i, 1872, pp.
217–232, 1 Fig.)

=Graber, V.= Ueber eine Art fibrilloiden Bindegewebes der Insektenhaut
und seine lokale Bedeutung als Trachealsuspensorium. (Archiv f.
Mikroskop. Anat. x, 1874, pp. 124–144, 1 Taf.)

—— Die Insekten; München, 1877. Organs of respiration, pp. 346–369.

=Packard, A. S.= On the distribution and primitive number of spiracles
in insects. (Amer. Naturalist, viii, 1874, pp. 531–534.)

—— On the nature and origin of the so-called “spiral thread” of
tracheæ. (Amer. Naturalist, xx, 1886, pp. 438–442, 2 Figs., p. 558.)

=Wolff, O. J. B.= Das Riechorgan der Biene nebst einer Beschreibung
des Respirationswerkes der Hymenopteren, des Saugrüssels und
Geschmacksorganes der Blumenwespen. (Nova Acta d. kais. Leop-Carol.
Akad. der Naturf., xxxviii, 1876, pp. 1–251, 8 Taf.)

=Palmén, J. A.= Zur Morphologie des Tracheensystems. Leipzig, 1877,
pp. 140, 2 Taf.

=Moseley, H. N.= Origin of tracheæ in Arthropoda. (Nature, xvii, 1878,
p. 340.)

=Poletajew, Olga.= Quelques mots sur les organes respiratoires des
larves des Odonates. (Horæ Soc. Ent. Ross., xv, 1880, pp. 436–452, 2
Pls.)

=Viallanes, H.= Sur l’appareil respiratoire de quelques larves de
Diptères. (Compt. rend. Acad. Sc., Paris, 1880, pp. 1180–1182.)

=MacLeod, J.= La structure des trachées et la circulation
peritrachéenne. Bruxelles, 1880, pp. 70, 4 Pls.

=Hagen, H. A.= Beitrag zur Kenntnis des Tracheensystems der
Libellenlarven. (Zool. Anzeiger, 1880, pp. 157–162.)

—— Einwürfe gegen Palmens Ansicht von der Entstehung des geschlossenen
Tracheensystems. (Ibid., 1881, pp. 404–406.)

=Macloskie, G.= The structure of the tracheæ of insects. (Amer.
Naturalist, 1884, xviii, pp. 567–573, Fig.)

=Haase, E.= Das Respirationssystem der Chilopoden und Symphylen
(Scolopendrellen) vergleichen mit dem der Hexapoden. (Zeitschr. f.
Ent. N. F., ix, Breslau, 1884.)

—— Das Respirationssystem der Symphylen und Chilopoden. (Zool.
Beiträge, von A. Schneider, i, 1884, pp. 65–95, 3 Taf.; Zool.
Anzeiger, 1883, pp. 15–17.)

=Grassi, B.= I progenitori degli Insetti e dei Miriapodi. L’Japyx e la
Campodea. (Atti d. Accad. Gioenia d. Sc. Nat. Catania, 1885, Sér. 3,
xix, pp. 83, 5 Pls.)

—— I progenitori dei Miriapodi e degli Insetti. Anatomia comparata dei
Tisanuri. (Reale Accad. d. Lincei di Roma, Anno 284, 1887.)

=Meinert, Fr.= De eucephale Myggelarver. Sur les larves eucephales des
Diptères. (Vidensk. Selsk. Skrifter., 6 Raekke, naturvid. og mathem.
Afd. Kjöbenhavn, 1886, iv, pp. 369–493, 4 Pls.)

=Cajal, S. R.= Coloration par la méthode de Golgi des terminaisons des
trachées et des nerfs dans les muscles des ailes des insectes.
(Zeitschr. f. wiss. Microscopie, 1890, vii, pp. 332–342, 1 Pl.)

=Wistinghausen, C. v.= Ueber Tracheenendigungen in den Sericterien der
Raupen. (Zeitschr. wissensch. Zool., xlix, 1890, pp. 565–582, 1
Taf.)

=Stokes, Alfred C.= The structure of insect tracheæ, etc. (Science,
1893, pp. 44–46, 7 Figs.)

=Sadones, J.= L’appareil digestif et respiratoire larvaire des
Odonates. (La Cellule, xi, 1895, pp. 271–325, 3 Pls.)

=Holmgren, Emil.= Über das respiratorische Epithel der Tracheen bei
Raupen. (Festschrift Lilljeborg. Upsala, 1896, pp. 76–79, 2 Taf.)
See also p. 437.

Also Gegenbaur’s Comparative Anatomy, Engl. Trans.

_b._ On the Stigmata

=Loewe, C. L. W.= De partibus quibus insecta spiritus ducunt. Diss.
inaug. Halæ, 1814, pp. 28.

=Sprengel, C.= Commentarius de partibus quibus Insecta spiritus
ducunt. Lipsiæ, 1815, pp. 38, 3 Taf.

=Dufour, L.= Recherches anatomiques sur l’Hippobosque des chevaux.
(Ann. Sc. nat., 1825, vi, pp. 299–322, 1 Pl.)

—— Nouvelles observations sur la situation des stigmates thoraciques
dans les larves des Bupresticides. (Ann. Soc. Ent. France, Sér. 2,
1844, ii, p. 203.)

=Landois, H.= Der Tracheenverschluss bei _Tenebrio molitor_. (Reichert
u. Dubois-Reymond’s Archiv f. Anat., 1866, pp. 391–397, 1 Taf.)

—— =und W. Thelen.= Der Tracheenverschluss bei den Insekten.
(Zeitschr. wissensch. Zool., xvii, 1867, pp. 187–214, 1 Taf.)

—— Der Stigmenverschluss bei den Lepidopteren. (Reichert u.
Dubois-Reymond’s Archiv f. Anat., 1886, pp. 41–49, 1 Taf.)

=Hagen, H. A.= Beitrag zur Kenntnis des Tracheensystems der
Libellen-Larven. (Zool. Anzeiger, 1880, pp. 157–162.)

—— Einwürfe gegen Palmén’s Ansicht von der Entstehung des
geschlossenen Tracheensystems. (Ibid., 1881, pp. 404–406.)

=Krancher, O.= Der Bau der Stigmen bei den Insekten. (Zeitschr.
wissensch. Zool., xxxv, 1881, pp. 505–574, 2 Taf.; Zool. Anz., 1880,
pp. 584–588.)

=Meinert, Fr.= Spirakelpladen hos Scarabæ-Larverne. (Vid. Meddel. Nat.
For. Kjöbenhavn (4), Aarg. iii, 1882, pp. 289–292.)

—— Noget mere om Spiracula cribraria og Os clausum. En Replik. (Ibid.
(4), Aarg. v, 1884, pp. 68–91, Fig.)

=Schiödte, J. G.= Spiracula cribraria—os clausum: lidt om
naturvidenskabelig Methode og Kritik. (Nat. Tidsskrift (3), xiii,
1883, pp. 427–473; also Jahresber. Neapel, 1883, p. 105.)

=Verson, E.= Il meccanismo di chiusura negli stimmati di Bombix mori.
(Atti Istit. Veneto. Sc., 1887, p. 9, Pl.)

—— Der Bau der Stigmen von Bombyx mori. (Zool. Anzeiger, 1887, x
Jahrg., pp. 561, 562.) See also Zool. Anzeiger, 1890, p. 116.

=Haase, E.= Die Stigmen der Scolopendriden. (Zool. Anzeiger, 1887, x
Jahrg., pp. 140–142.)

—— Holopneustie bei Käfern. (Biolog. Centralbl., 1887, vii, pp.
50–53.)

=Carlet, G.= Note sur un nouveau mode de fermeture des trachées,
“fermeture operculaire” chez les insectes. (Comp. rend. Acad. Sci.
Paris, 1888, cvii, pp. 755–757.)

=De Meijere, J. C. H.= Über zusammengesetzte Stigmen bei
Dipterenlarven [etc.]. (Tijd. Ent., xxxviii, 1895, pp. 65–100, 33
Figs.)

Also the other writings of Palmén, Dufour, Dewitz, Boas, Verson.

_c._ On tracheal gills and tracheal respiration

=Pictet, F. J.= Mémoires sur les larves des Némoures. (Annal. Sc.
nat., 1832, xxvi, pp. 369–391, 2 Pls.)

—— Recherches pour servir à l’histoire et à l’anatomie des
Phryganides. Genève, pp. 235, 20 Pls.

—— Histoire naturelle générale et particulière, des insectes
Neuroptères. I, Monographie: Famille des Perlides, Genève, 1841,
1842, pp. 423, 53 Pls.

—— Histoire naturelle générale et particulière des insectes
Neuroptères. II, Monographie: Famille des Ephémérines. Genève,
1843–1845, pp. 300, 47 Pls.

=Dufour, L.= Recherches anatomiques et considerations entomologiques
sur les insectes Coléoptères des genres Macronychus et Elmis. (Ann.
Sc. nat. Zool., Sér. 2, 1835, iii, pp. 151–174, 1 Pl.)

—— Description et anatomie d’une larve à branchies externes
d’Hydropsyche. (Ibid., Sér. 3, 1847, viii, pp. 341–354, Fig.)

—— Recherches anatomiques sur la larve à branchies extérieures du
_Sialis lutarius_. (Ibid., Sér. 3, 1848, ix, pp. 91–99, Fig.)

—— De diverses modes de respiration aquatique chez les insectes.
(Compt. rend. Acad. d. Sc. Paris, 1849, xxix, pp. 763–770; Ann. and
Mag. Nat. Hist., Sér. 2, 1850, vi, pp. 112–118.)

—— Études sur la larve du Potamophilus. (Ann. Sc. nat., Sér. 4, xvii,
1862, pp. 162–173, 1 Pl., Bericht v. Gerstaecker f. 1862, pp. 16,
17.)

=Grube, A. E.= Beschreibung einer auffallenden an Süsswasser-schwammen
lebenden Larve (Sisyra). (Wiegmanns Archiv f. Naturgesch., 1843, ix,
pp. 331–337, Fig.)

=Schröder van der Kolk, J. L. G.= Mémoire sur l’anatomie et
physiologie de _Gastrus equi_. (Nieuwe Verhandl. d. K. Nederl.
Instit. Amsterdam, 1845, ix, pp. 1–155, 13 Pls.; Erichson’s Bericht.
f. 1845, p. 109.)

=Scheiber, S. H.= Vergleichende Anatomie und Physiologie der
Œstriden-Larven. Respirationssystem. (Sitzungsber. Akad. Wissensch.
Wien. Math.-naturw. Cl., 1862, xlv, pp. 7–39.)

=Lubbock, J.= On the development of _Chloëon dimidiatum_. (Trans.
Linn. Soc. London, I, 1868, xxiv, pp. 61–78, 2 Pls.; II, 1866, xxv,
pp. 477–492.)

=Oustalet, E.= Note sur la respiration chez les nymphes des
Libellules. (Ann. Sc. nat. Zool., Sér. 5, xi, 1869, pp. 370–386, 3
Pls.)

=Rolph, W. H.= Beitrag zur Kenntnis eininger Insektenlarven. 1 Taf.
Inaug. Dissertat. Bonn, 1873.

=Chun, C.= Ueber den Bau, die Entwicklung und physiologische Bedeutung
der Rektaldrüsen bei den Insekten. Frankfurt a. M., 1875.

=Haller, G.= Die Stechmückenlarve. Kleinere Bruchstücke zur
vergleichenden Anatomie der Arthropoden. I. Ueber das Atmungsorgan
der Stechmückenlarven. (Archiv f. Naturgesch., xliv, 1878, pp.
91–96, 1 Taf.)

=Vayssière, A.= Recherches sur l’organisation des larves des
Ephémérines. (Ann. d. Sc. nat. Zool., Sér. 6, xiii, 1882, pp. 1–137,
11 Pls.)

—— Monographie zoologique et anatomique du genre Prosopistoma Latr.
(Ibid., Sér. 7, ix, 1890, pp. 19–87, 4 Pls.)

=Eaton, A. E.= Notes on some species of Cloëon. (Ann. Mag. Nat. Hist,
Ser. 3, xviii, 1866, pp. 145–148.)

—— A revisional monograph of recent Ephemeridæ or may-flies. (Trans.
Linn. Soc. London, 1883–1887, Ser. 2, iii, 63 Pls.)

=Müller, Wilh.= Ueber einige im Wasser lebende Schmetterlingsraupen
Brasiliens. (Archiv f. Naturgesch., 1884, i Jahrg., pp. 194–212, 1
Taf.)

=Vogler.= Die Tracheenkiemen der Simulien-Puppen. (Mitteil. Schweiz
Ent. Gesellsch., 1887, vii, pp. 277–282.)

=Raschke, E. W.= Die Larve von _Culex nemorosus_. Ein Beitrag zur
Kenntnis der Insekten-Anatomie und Histiologie. (Archiv für
Naturgesch., 1887, liii Jahrg., pp. 133–163, 2 Taf.; Zool. Anz.,
1887, x Jahrg., pp. 18, 19.)

=Klapálek, Fr.= Untersuchungen über die Fauna der Gewässer Böhmens. I.
Metamorphose der Trichopteren. (Archiv f. naturwissensch.
Landesdurchforschung von Böhmen, Prag, 1888, vi, No. 5, pp. 63; No.
6, 1893, pp. 145, Figs.)

=Müller, Fritz.= Larven von Mücken und Haarflüglern mit zweierlei
abwechselnd thätigen Atemwerkzeugen. (Ent. Nachr., 1888, xiv Jahrg.,
pp. 273–277; also Zool. Anzeiger, iv, 1881, pp. 499–502.)

=Kolbe, H. J.= Ueber den Kranzförmigen Laich einer Phryganea.
(Sitzungsber. d. Gesellsch. naturforsch. Freunde in Berlin, 1888,
pp. 22–26.)

=Haase, Erich.= Die Abdominalanhänge der Insekten mit Berücksichtigung
der Myriopoden. (Morpholog. Jahrbuch, 1889, xv, pp. 331–435, 2 Taf.)

=Dewitz, H.= Einiger Beobachtungen, betreffend das geschlossene
Tracheensystem bei Insectenlarven. (Zool. Anzeiger, xiii, 1890, pp.
500–504, 525–531.)

=Miall, L. C.= Some difficulties in the life of aquatic insects.
(Nature, xliv, London, 1891, pp. 456–462.)

—— Natural History of aquatic insects, 1895, 116 Figs., pp. 1–395.

=Weltner, W.= (Note on Sisyra.) (Ent. Nachr., p. 145, 1894.)

Also papers by Hagen, Dewitz, Williams, Tömösváry (1884).

_d._ Literature on rectal respiration

=Suckow, F. W. L.= Respiration der Insekten, insbesondere über die
Darmrespiration der _Æschna grandis_. (Zeitschrift f. d. organ.
Physik, von Heusinger, 1828, ii, pp. 24–29, 4 Taf.)

=Dufour, L.= Sur la respiration branchiale des larves des grandes
Libellules comparée à celle des poissons. (Compt. rend. de l’Acad.
Sc. Paris, 1848, xxvi, pp. 301–303.)

—— Études anatomiques et physiologiques et observations sur les larves
des Libellules. (Ann. Sc. nat. Zool., Sér. 3, 1852, xvii, pp. 76–97,
3 Pls.)

=Gilson, G. and J. Sadones.= Larval gills of Odonates. (Journ. Linn.
Soc. London, 1897.)

_e._ Physiology of Respiration

=Bonnet, Ch.= Recherches sur la respiration des chenilles. (Mém. Math.
des Savants Étrangers, Paris, 1768, v, pp. 276–303.)

=Treviranus, G. R.= Biologie, oder Philosophie der lebenden Natur, für
Naturforscher und Aerzte. 6 Bände, Göttingen, 1802–1822. (Atmung, in
Bd. iv.)

—— Die Erscheinungen und Gesetze des organischen Lebens. 2 Bände,
Bremen, 1831–1833. (Atmung der Insekten in Bd. i.)

—— Versuche über das Atemholen der niederen Tiere. (Zeitschrift f. d.
Physiologie, von F. Tiedemann, G. R. u. L. C. Treviranus, 1832, iv,
pp. 1–39.)

=Hausmann, J. F. L.= De animalium exsanguinum respiratione
commentatio. Hannover, 1803, vi, p. 70.

=Spallanzani, L.= Memoirs on respiration. London, 1804.

=Sorg, F. L. A. W.= Disquisitiones physiologicæ circa respirationem
insectorum et vermium. Rudolstadt, 1805, Part II, p. 146.

=Nitzsch, C. L.= Commentatio de respiratione animalium. Vitebergæ,
1808, 4º, pp. 56.

—— Ueber das Atmen der Hydrophilen. (Reil’s Archiv f. Physiologie,
1811, x, pp. 440–458.)

=Reimarus, J. A. H.= Ueber das Atmen, besonders über das Atmen der
Vögel und Insekten. (Reil u. Autenrieth, Archiv f. Physiologie,
1812, xi, pp. 229–236.)

=Dufour, L.= Anatomie de la Ranatre linéaire et de la Nèpe cendrée.
(Annal. génér. Scienc. phys., Bruxelles, 1821, vii, pp. 194–213, 1
Pl.)

—— Mémoire pour servir à l’histoire du genre Ocyptera. (Annal. Scienc.
natur., 1827, x, pp. 248–261, 1 Pl.)

—— Recherches sur quelques entozoaires et larves parasites des
insectes Orthoptères et Hyménoptères. (Ann. Sc. nat. Zool., Sér. 2,
1836, vi, p. 55; Sér. 2, 1837, vii, pp. 5–20.)

—— Note sur le parasitisme. (Compt. rend. Acad. Sc. Paris, 1851,
xxxiii, pp. 135–139; Rev. et Mag. de Zool., 1851, pp. 408–412.)

=Dutrochet, R. J. H.= Du mecanisme de la respiration des Insectes.
(Ann. Sc. nat., 1833, xxviii, pp. 31–44; Mém. Acad. Sc. Paris, 1838,
xiv, pp. 81–93.)

=Newport, G.= On the respiration of insects. (Phil. Trans. Roy. Soc.,
London, 1836, cxxvi, pp. 529–566.)

=Coquerel, Ch.= Note pour servir à l’histoire de _l’Æpus robini_.
(Ann. Soc. Ent. France, Sér. 2, 1850, viii, pp. 529–532.)

=Davy, J.= On the effects of certain agents on insects. (Trans. Ent.
Soc. London, 1851, pp. 195–212.)

=Barlow, W. F.= Observations of the respiratory movements of insects.
(Phil. Trans. Roy. Soc. London, cxlv, 1855, pp. 139–148.)

=Rathke, H.= Anatomisch-physiologische Untersuchungen über den
Atmungsprozess der Insekten. (Schriften d. k. phys.-ökon. Ges.
Königsberg, i Jahrg., 1860, pp. 99–138, 1 Taf.)

=Lubbock, J.= On two aquatic Hymenoptera, one of which uses its wings
in swimming. (Trans. Linn. Soc. London, xxiv, 1863, pp. 135–142, 1
Pl.)

=Boyle, R.= New pneumatical experiments about respiration. (Phil.
Trans., 1870, v, No. 63, pp. 2051–2056.)