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Psyche 3:263-275, 1880.

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PSYCHE.
FRAGMENTS OF THE COARSER ANATOMY OF DIURNAL LEPIDOPTERA.
1.
THE LARVA OF DANAIS PLEXIPPUS, OF NORTH AMERICA. BY SAMUEL H. SCUDDER, CAMBRIDGE, MASS.
So very little is known of the points in which different lepidoptera agree or dis- agree in their internal anatomy, that,
although very fragmentary, I venture
to publish the following accounts of dis- sections of caterpillars and chrysalids of butterflies, made about ten years ago,
more in the hope of calling attention to the need of work
of this kind than of di-
rectly contributing to any general state- ments deducible from the observations;
The literature of the subject is exceed- ingly scanty. Swammerdam in his
Biblia naturae (1737) gives illustrations anddescriptions of the internal anatomy of the larva of Aqlais urticue; Herold in his Entwickelungsgeschichte der Schmet-
terlinge (1 815) gives admirably full de- tails of the anatomy of both larva and
pupa of LL Pieris brassicae " ; Newport
gives a section
on the Development of
the nervous column of " Vanessa urti-
cae" in the Philosophical transactions
for 1834 (repeated in Todd's encyclo-
paedia, art. Insecta) : and on the
Transformations of the tracheae in the
same insect in the Philosophical trans-
actions for 1836 (also repeated as
above) ; Brandt also figures the meta-
morphoses of the nervous system of
the same species in the Horae societatis entomologicae rossicae for 1879. v. 15,
pi. 14 ; and in my recent volume on but- terflies, quoted below, I have given a
brief account of the anatomy of larvae
of butterflies in general and of the
changes the organs undergo in passing
through the pupal condition.
So far as
I am aware, these are all the notices
that have been published of the internal anatomy of the earlier stages, and, as
will be seen, they cover a very narrow
field, treating, with the exception of my little book, of only two species.
My studies were mostly confined to
half a dozen insects, which will be sep- arately treated, commencing with the
highest, the account of which will also be fullest.
A good illustration of the general dis-
position of the organs of the caterpillar of Damis plexippus, drawn on a side
view by Mr. Edward Burgess, will be
found in my recently published book on
butterflies,* fig. 78, and this may be
-
*Butterflies : their structure, changes and life histo- ries, with special reference to American forms. . . . New York. Henry Holt & Co., 1881.8?




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PSYCHE.
readily wed in connection with the fol- of the body ; each is made up of a series lowing description.
of bands, one to each segment, extending Muscular system. The head is mostly across its entire length, and they are filled with conical muscular bundles, at- permeated by minute tracheal vessels tached by their bases to the upper and running mainly at right angles to the di- lateral portions of tbe posteriortwo-thirds, rection of the fibres ; from the anterior and to some extent to the upper portion of end of the inner strip of each segment, a the anterior third of the vault of the head ; slender muscular strap runs obliquely to the apices of these conical masses eon- the middle of the ventral line of the seg- verge toward the middle longitudinal line meat. Above the spiracles, on each of each hemisphere, and then pass side, are three muscular ribbons, the downward, terminating, in the lower half lowermost lying nearer the integument of the head, in a white, glistening, mdi- than the others, its lower edge touching nous cord fully a mitlimetre long, lying just the tease of the tracheae. Beneath all behind the optic nerve and reaching flown these longitudinal bands, as seen from into the mandibles,
which they serve to within, i. e., lying nearer the integument, ctn~e The extflnsors of the mandibles and at the anterior edge of each segment, are attached behind and below the eye- a narrow transverse belt encircles the specks, and pass directly to the outer whole body, passing at the stigmata1 line base of the mandibles, which they enter over the longitudinal tracheal vessel by means of a tendon attached to the in- which unites two contiguous spiracles, terior wall of the same. The retractors and strapping it to the integument, of the labrum are slight, flat,, muscular The flexor muscles of the true legs ribbons, attached at one extremity along originate in the body just beneath the the whole of ite upper interior edge origin of the outer of the two Iongitn- and at the other to the facial triangle; dinal muscular ribbons of the ventral the labrum is drawn inwards by a double surface of the body, and extend to the muscle, which starts above from its at- opposite wall of the segment. The taclunent along each side of the median mnsclee of the pmlegs consist of flat suture above the facial triangle, and bands forming a muscular coating to the passes freely downwards, the muscles of walls of the legs, passing in a direct the two aides confluent and together 0.88 line downward, narrowing; as they go ; mm. broad, diminishing in breadth down- they do not cross each other, nor pass ward, and terminating in a single tendon to opposite sides of the legs, but are en- attached to the middle of the labnmf. tire17 simple. A band or ribbon, made up of simple, Passing now to the tausclea attached to longitudinal, parallel muscular fibres, col- the internal organs, we find the coating lected into two contiguous strips, the of the stomach, which is a mere film inner the narrower, runs from one end of overlaid by delicate parallel strips the body to the other, near the akin, be- mueculm fibres cro~sing diagonally in twee~ the spiracles and the ventral line opposite directions ; beaides these there



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PSYCHE.
are longitudinal muscles arranged in sets; dinal and transverse muscular bands,
each set separated from its neighbors
heavier than those on the stomach-WSU-
by an interval of about one millimetre,
Digeathe ayatem. The -oesophagus ie
and composed of four slender bands,
a simple, straight, equal tube 1.5 mm.
traversing the entire length of the stom- long, terminating posteriorly in a lar-
ach; those next the dorsal and ventral
ger portion swollen in the middle and
lines are more prominent than the others better provided with muscular bands,
and on the anterior are larger than on
3.5 mm. long and 1.75 mm. broad - a
the posterior half; the sets on the dorsal sort of crop, which extends part way
line are united into a double band at
into the second thoracic segment. The
the anterior extremity and pass to the
stomach extends from the middle of the
oesophagus, where they are more widely second thoracic to the middle of the separated ; the oesophagus is provided seventh abdominal ~egment and of conrae also with other longitudinal muscles, and varies in size according to the amount to ft less extent with transverse emir- of food the creature has swallowed ;, cling bands. The small intestine 13 usually it is shout 4 mm. in diameter ; covered with both transverse and longi- the proper wall of the stomach eeems to tudinal bands of thick white and glisten- be the merest film, traversed by nms-
ing muscular tissue ; at ita anterior end cular fibres, which, by lines) not deeply especially, where the alimentary canal impressed, divide the surface into narrow, is greatly constricted, it is covered thick- rounded, transverse, parallel lobes, reach- ly with short longitudinal muscles, whose ing from the middle of the upper and
hinder extremities dovetail into other
under surfaces to the middle of each side, longer sets; beside8 these, there arise
and which alone prevent the perfectly
from the middle of the posterior end
free and direct posterior motion of the
of the intestine a number of parallel contents. The stomach itself, however, bands of muscnlar fibre, which embrace may be wholly withdrawn, without mp- it diagonally, passing around to the tare, from this investing muscular tissue. ventral surface of its anterior extremity ; At the middle of the seventh abdominal starting just in front of the posterior segment, the alimentary canal suddenly insertion of these, and interlacing with tapers, and the mall intestine cornmen- them at right angles, is another shorter ces, extending half-way to the end of
set of parallel muscles, whose other the body and consisting of a straight extremities are attached to the body- cylindrical tabe 2.25 nun. in diameter, wall ; still further, a set of four indepen- surrounded by thick walls of muscular dent parallel muscular bands passes tissue, the longitudinal bands of which neath and supports the posterior end of mold the interior walls into very promi- the small intestine, reaching horizontally nent longitudinal ridges. The colon is
from the middle of one side of the eighth a simple straight tube of the same size as abdominal segment to the opposite.
The the intestine but capable of considerable colon is furnished simply with expansion, and with a smooth inner



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266 PsrcHE.
surface.
first abdominal segment ; a11 three branch- The salivary glands are a pair of long
es pass outside the tracheal tubes which straight, flat ribbons, arising from each invest the stomach, and when each has
side of the anterior extremity of the returned to the point from which it oesophagus and extending backward started, the extremities of the three along the alimentary canal; tliey are
threads are collected with those of the
4.75 mm. long, tapering slightly and opposite side, in a single intricate aucl regularly to a bluntly rounded tip, being convoluted mass enveloping the intea- 0.34 mm. broad near the base and 0.14 tine, and covering also the whole surface TDIB. broad close to the tip ; they rcsem- of the colon with their more delicate ble flattened, braided cords, being corn- terminal threads. When the posterior
pressed along the median line, while part of the alimentary canal is pressed, each side is regularly and deeply excised whitish particles can be seen to move in at frequent intervals, producing bead- an irregular manner within the malpi-
like lateral prominences. ghian vessels. The malpighian vessels originate as Respiratory System. The tracheae of slender tubes, one on each side of the
the first abdominal segment are larger
middle of the anterior half of the intes- and branch more extensively than those
tine ; the tube gradually enlarges, and
of any other segment, their ramifications at a distance of 2 mm. from the origin
extending to the anterior extremity of
subdivides into three branches (the un-
the stomach; while those of the third
der branch originating just before the
thoracicsegment are small and cornpar-
other two), which are strongly waved or
atively inconspicuous and are connected
crennlated cords, and are, throughout,
with those of the first abdominal seg-
nearly or quite as large as the tube at
ment by only a small longitudinal canal ; its very origin ; the under branch passes the first thoracic segment bears, however, forward in a tortuous course, above the
an extensive bunch of tracheae, which is nervous cord, along and in contact with
connected with that of the first abdomiu- the under outer surface of the stomach,
al segment by a long longitudinal canai, as far as the middle of the first abdorn- as large as many of the main branches
inal segment, where it bends upon itself of these two segments.
and returns in a similar manlier, a The anterior braiicb of this bnnch in little higher up, to the point from which the iiwt thoracic segment supplies the it started; the two other branches, head; it passes upward on each side which are a little smaller than the first, along the hinder edge of the head, extend forward and then backward in until it meets that of the opposite a similar manuer, one passing along the sides, when the two join so strongly that upper outer portion of the stomach as considerable force is required to part
far as the second abdominal segment, them ; and the only mark of separation and then returning, the other along the is a pale line on the dusky surface. As
side of the stomach to the middle of the soon as they meet they bend toward the



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PA 7 L'HA .
26 6
head, separate again and run side by side straight course toward the ocelli ; as -
beneath the muscular mass which occn-
pies most of tlic head, over the double
the Librum. Before these two opposite
branches first unite they emit from their ....... ....... ....... ... ..
emhraes the muscular maw from lielow ;
half way between the spiracle and the
top of the head, this arching branch
-
it reaches them it expands in
broad field comprising the ocelli,-
conical masses, their apices plunged
tending; to the nppsr portion of the ten- dinom cord which terminates the great
.......................
the mandibles.
A tittle further ~wmovecl
from the optichnerve. and on the lower
anterior edge of each lobe. a little within . . -<. . . .
rl seems to b~ compoaed of an execs-
clv delicate, whitish, pellucid film,
scarcely 0.5 mni. in diameter, uni-
m ~thronglhoat. and terminates at
--
rounded tip.
Tervm'.s system. Viewed from above,
the cephalic ganylia eoii~iat of a pair of short, obo-i-ate, nearly g'loht~lar lobes, which nins in a straight course to the
hwe of the antennae.
From the lower outer edge of each
..........
abo~~ its hinder edge ; jnst beneath the oesophagus -thpse embraeins; cords fire
united bv a cross thread ; this an1-i-
.. , 3 . .
a spccyndaq+ muscle, which runs bac
ward beside the cord for n, short distm
divaricating- slightly.
The ganglia of the body-segments




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PSYCHE.
one behind the other, and with these the the cords between the second and thud
nervous cord terminates.
All the gan- ganglia, and which is aeen to be double glionic disks are connected by a pair of only by the slight divergence of the ribbons, generally lying in such close cords in advance of each ganglion' as proximity as to appear to be single and they enter it. The last ganglion is straight, but anteriorly they are separa- situated in the seventh abdominal seg- fed somewhat widely.
men& just posterior to the tenth ganglion ; In leaving the suboesophageal gan- indeed the two appear almost to coalesce glion, the nervous ribbons ran nearly at their adjoiningedges; the eleventh ia, parallel, or only slightly curved outward, atighfcty the larger of the two. From
to the first body-ganglion. Starting the second abdominal segment backward, again dose together at the middle of the the nervous cord does not come in direct posterior border of the first ganglion contact wife the alimentary canal, but they diverge in straiff6t liwa, but very considerable fatty tissue is interposed gradually, for fully two-thirds the distance between them ; in advance- of thi~, how- to the second ganglion (which is twice ever, the reverse ie the case, the fatty as far removed from the first as the first tissue appearing aa if strapped in its is from the suboesophageal ganglion), place between the nervous cord and where they are nearly twice as far apart the integument by the branches of the aa the width of t,he first ganglion, and former. then converge more rapidly and enter From each side of each abdominal the second ganglion at its outer anterior ganglion two lateral nerves are emitted, border. The distance from the second
the anterior at right angles, the posterior to the third ganglion is effected in a
in a slightly posterior direction, aud at similar manner, the distance from the their bases the two are connected by a second ganglion to the point of greatest delicate film. Jn the thoracic segments . divergence being about eqnal to the dis- a similar rule holds, bat in the first tance between the first and second gang- ganglion only the anterior lateral nerve lia.
The fourth ganglion is but little is present, and it is directed forward ; the removed from the third, being in fact
third ganglion on the other band fol-
nearer to it than the latter is to the point lows the rule of the abdominal ganglia,
of greatest divergence of the ribbons in while in the second, the nerves are wn-
advance of it; between these two gan-
fluent at their origin, directed at right glia the ribbon is straight, slightly longer angles outward, and almost immediately
than broad, broader than at any point,
diverge at right angles to each other, one posteriorly, and its separation into two forward, the other backward. In addi-
cords is not, readily seen. Behind this
tion to the lateral nerves, the terminal the ganglia are nearly equidistant (up to ganglion is farni~hed wtth two pairs of
thoee of the seventh abdominal segment.) longer and stouter posterior nerves, and connected by a straight double rib- reaching into the hinder segments, the bon, scarcely .broader than either one of outer cords trending somewhat outward.



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JPS rcHB. 269
Silk vessels. These, whiiih have their soft, plump, kidney-shaped, compound outlet upon the labium, consist first of organs, 2.5 mm. long, of a bluish-purple a delicate thread running along the sides color, covered by an exceedingly thin
of the alimentary canal in a tortuous
whitish investment, concealing the color close to the stomach as far as the middle of the third abdominal segment ; here it JA^l^*W ....*.. ^~^Tlb' --a -*llL*,-..., ^-- ^La - ."
its course on the tinder surface of the
stomach ia 18 mm. ; chiring its tortuous . ,. I . OK, -.... * :^f. ___A<______-l^-llinl, ness, 0.8
d within a dis
tan% of
ening.
nner to the middle of the second
of the interior as by a pale bloom.
In
cic segment ; here, at the lower a longitudinal row along the middle of on of the sides of the stomach, they
r
licken rapidly and form the second 7
rtion, a slender tube of uniform size,
B
running in a etraight course beside dud z UUICIa IJV El bULU pEULllJlUU WtliH; bI1Q middle pair of chamhers is smaller than
UUUIAEB ~ p u ~ iiiacii. ULL EMUUE~ w iiiu the onter one, and they are all filled with middle of the preceding segment, again
a grayish granular matter.
From the
repeating the- curve in a. reverse direction anterior extremity of each teatis runs a for half the distance, and then passes short white thread, not. half so long as upward to the upper surface of the atom- the testis, and thickened in the middle
a& and continues in a tortnoua course.
and at the end. Jnet behind the hind-
.
still htigging the. alimentaq canal, aa most spot of each eide, a, delicate pellu- far as th~ sixth aMomind segment, cM thread ariaea, which pagees poste- where it terminates in a very slender
riorly and a little downward until oppo- straight thread, by which it is connected site the spiracle of the sixth abdominal with the sides of the intestine. The
length of the basal thread is 12 mm.,
covering a distance of 4 mm. ; the
length of the thickened portion during suvuu, nwccua WWWL wwuu HIW~U-
ventral line of the hay, and, passing
through an independent muscular bundle
LVU~S~; ~UUW. o.~ WIU. i 11,- JLUI IUHI Liiiun- ~c&rcely larger than itself, which stretches transversely across the body at this
- point, enters a. whitish sac about 0.75 mm. long* situated jnst beneath the ter- generative organs. The testes mination of the intestine ; the threads abd in the middle of the dmmm
me hmt 13.5 m. 10% and 0.03 mm.
f the fifth abdominal segment directly
bove and upon the stomach ; they are
the inner side of each half, there are fou minute roundish spots of a deeper color
each communicating with a aeparata
chamber within, separated from thi
,dl.*"" L.. A &L!- -*LA:-- --la . A,.
segment ; here it plunges downward
toward it, and passing through the mass
of tracheae to those of the aeventh seg- .,.m.-.+ *-A*.... *"......A b---..d &LA --A:-



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2 70 PS YCHE.
is shaped in the 7-days' chrysalis much
In the middle of the thorax the sali-
as in the pupa of ffamad'iyas io, to be vary glands form exceedingly fine, described further on, and is about 5.25 crinkled threads, which here collect in a mm. long, scarcely 1 mm. broad, cylin- longitudinally disposed mass on each drical, and at tip bluntly and regularly side of and touching the oesophagus ; rounded ; in the 9-days' pupa it is flat- this mass extends over a distance of 2.5 Wed, increasing regularly and con- mm. and the thread finally ends in a siderably in size, and at the tip slightly bulbous enlargement about 0.2 mm. in and roundly invaginate ; it reaches to the diameter. third abdominal segment, being 4.6 mm.
The malpighian vessels begin to branch
long, and its greatest breadth 2.5 mm.
at a distance from their origin ~carcely Next the opening to the "jabot," the greater than their diameter, and the intestinal canal expands to a sort of eecond division occura at even a less crop, of an oval shape, scarcely longer distance beyond the first; one of the than broad, and about 1 mm. long ; this latter branches extends along the su- opens directly into the stomach, a perior lateral walls of the stomach, as cylindrical tube, tapering in front, about far as the middle of ite anterior half 8 mm. long, suddenly contracted at its (perhaps farther, later in life) and then posterior end. The intestine in a 7- returns; the other brafioh of the outer days' chrysalis is a rather large, cylin- set passes along the inferior lateral walls drical tnbe, fully 6.5 mm. long, and 3 of the stomach; they are all very mm. broad, slightly tortuous, especially delicite, memuring but 0.04 mm. in anteriorly; in the Maya' chrysalis, diameter, and after their retim are however, considerable change has been strongly convoluted, enwrapping the effected, for the intestine is now 9 mm. . intestine but not the colon- long, and only 0.25 mm. in diameter, Resptnttmy system. The branchial a little larger at the. two extremities, 'tobea in the posterior part of the body bnt otherwise equal and much more are amall, but from the third abdominal tortuous ; at first it is directed upward, å´segment forward they commence to forward and slightly to one aide for a enlarge ; this - i ~ especially noticeable in