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Psyche 8:207-210, 1897.

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Psyche, Vol. 8. Plate 5.




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PSYCHE.
A STUDY OF THE CATERPILLARS OF NORTH AMERICAN SWALLOWTAIL BUTTERFLIES.* - I.
BY SAMUEL H. SCUDDER, CAMBRIDGE, MASS,
Interesting as are the transforma-
tions of a butterfly in the three eailie~ periods of its life, marked off' by such strict lines from one another, the
changes which the same insect under-
goes in shape, in color and in clothing
in the different stages of caterpillar life alone, are scarcely less surprising.
This is true to so marked an extent in
the caterpillars of our swallowtails
that if in their earliest stages they were only large enough to have all their
peculiarities readily seen by the naked
eye, more attention would long ago
have been given them. It is also im-
portant on other grounds Weismann
has mentioned the desirability of stndy- ing the early stages of these caterpillars in particular, to acquire a knowledge
of their phylogeny. and they have
formed the subjcct of an extended but
still incomplete paper by Grnber,t
somewhat barren in results from its
incompleteness, and in some particu-
complete material now at hand, studied
almost entirely from fresh objects, the
extraordinary variety among our "New
England forms, and the curious fact
that these cover almost the entire range of variation known among the caterpil-
lars of Papilionini the world over lend
special interest to such an enquiry.
I propose in the first place to give
for each of the six species of our fauna, each representing a distinct genus, as
succinct an account as possible of the
several important changes ; next, to
summarize from this the leading lines
along which the changes have occurred ;
and finally to diaw from the facts such
conclusions as seem admissible.
The caterpillar of Laertias-philenor
(Fig. I.) at birth is uniformly cylindri- cal, of a uniform dark brown, covered
with several rows of conical warts of
neatly uniform size, most of them bear-
ing a single bristle, a few, on the
lass from its inaccuracy. The more
*Reproduced with slight changes from the author's Butterflies of the Eastern United States and Canada, pp. I234-IUI.
t Jen. zeitschr. naturw., xvii; Papilio, iv. thoracic segments and just above the
abdominal legs, more than one. In its
second stage the shape and coloring are
the same as before, but the clothing of
the body is greatly changed, for all the warts bearing: single bristles have dis-



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208 PSYCHE. [May &a.
appeared, together with their bristles,
and so have the bristles of the other
warts, but in these latter instances the warts remain, and have become short,
fleshy, often brightly colored filaments ; while to take the place of the simpler
warts a new and independent series of
fleshy filaments has arisen between
the two series which disappeared,
The remaining stages are much the
same as this, only the filaments at the
extremities of the body grow longer
and longer with each stagc, more and
more highly colored ; a suprastigmatal
series of coral red spots is introduced in the fourth stage on some of the ahdomi-
nal segments ; and finally, in the last two stages, the thoracic segments taper for- wards markedly.
The new-born Iphiclides ajax (Fig.
2) is cylindrical, but a little larger in front than behind, of a nearly uniform
dark leaden color, darker, however, on
the front half than behind, covered with rounded warts arranged in several rows,
a few at the extremities slightly larger than the others, most of them support-
ing a number of bristles, generally
widely forked at the tip. In the sec-
ond stage every trace of tubercles and
bristles, forked or simple, has gone,
excepting a few slight, spineless warts
at the extremities, and in their place
fine, excessively short hairs are scat-
tered over the body ; this has become
tumid on the thoracic segments, and is
transversely striped with uniform black
and white or yellowish bands, of which
there are many to a segment. In the
third stage the hairs are even less oh-
servable, and the stripes have become
finer and tremulous, while the incisure
between the last thoracic and first ab-
dominal segment is marked by a broad,
black, velvety stripe, edged in front
with white and behind with yellow.
The fourth stage shows no special
change. In the fifth the broad, velvety
stripe becomes more conspicuous, be-
cause the ordinary stripes become more
or less obsolete ; and when full grown
the latter often or generally persist only as transverse series of black dots on a
nearly uniform green body, though the
yellow stripes remain, at least on the
sides.
In Jzsoniades glaucits (Fig. 3) the
infant caterpillar is cylindrical, slightly tumid anteriorly, of a dark brown or
sometimes even velvety black color, a
little paler beneath, the extremities light- er, and an oblique stripe in the middle
above on each side, forming a sort of
saddle-shaped whitish mark ; the body
is covered with several series of wart
like tubercles, larger at the extremities than in the middle of the body, beset
with bristles. In the second stage
tubercles and bristles are gone, except- ing at the extremities of the body, where they are relatively much reduced ; the
color and markings remain much as
before, but are perhaps more diversi-
fied, and have added to them on the
sides of many of the segments next the
tubercles a minute bluish spot, that of
the third thoracic segment (now more
distinctly tumid) with a velvety black
streak below it. In the third stage all
the markings are still more distinct and



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May 1898.; J's yc~%!??. 209
diversified, and the tubercles have
ahnost entirely disappeared and been
replaced by smooth, shining lenticles,
while on the sides of the third thoracic segment the black spot and black streak
have developed to a black an~~nlus with
a blue center. In the fourth stage the
general color becomes at first a dark
brownish olivaceous, with the same
striking contrasts as before, but during the course of this stage this is replaced by a grayish green, and the saddle,
which has been becoming yellow, fades
and diminishes until a mere ghost re-
mains; the first abdominal segment is
edged behind with yellow, the lenticles
have turned to coloi'ei.1 spots, and on
the third thoracic segment is seen at
first a pair of roseate spots faintly
edged with black, and a black line
between them, afterwards becoming a
single yellow spot, including below a
luteous lenticle, above a velvety black
streak, and in the middle a black-
rimmed, turquoise spot. In the final
stage the caterpillar becomes pure
green above, pale bluish green below,
and the only markings are a bright,
transverse stripe of black and yellow at the hind edge of the first abJoinina1
segment, a few rows of minute dark
turquoise spots, and on the sides of the third thoracic segment a still further
development of the markings, the whole
now forming a rounded, quadrangu-
lar, greenish yellow spot, rimmed del-
icately with black, crossed above by a
black bar, and enclosing below a black
aimiilus with a turquoise centre.
In Euphoeades troilus (Fig. 4) we
start in pnictically tlie same way as in Jnsoniades, only the saddle is less ob-
lique. In the second stage the cater-
pillar is plumbeous, with the lateral
flaps of the pale saddle more distinct
than the seat, 'the body paler below
than above, and there is added a curv-
ing white streak below the middle of
the sides of the thoracic segments,
seeming to define better the tumid front portion of the body; bluish dots appear
along the dorsal part of the segments,
and on the third thoracic segment one
at the side is velvety black, edged above and below with yellow; the tubercles
are only distinct at the extremities of
the body. The third stage hardly dif-
fers from the second, but the spot on
the third thoracic segment is now larger zind wholly rimmed with yellow. The
fourth stage also closely resembles the
preceding, but the tubercles are re-
placed by lenticles, one on the third
thoracic segment black and glistening,
and included in the black spot. The
last stage is wholly different, the gen- eral color being a pure green, on which
only the minor spots remain as links to
the past, and reinforced by others which replace the lenticles; the spot of the
third thoracic segment has altered ; it
is now a finely black-rin~mecl, large,
orange and yellow spot, including a.
quadrate black nucleus below the mid-
dle, nearly half as large as the whole
spot, and including within it posteriorly a shining black, blue-edged lenticle;
a thin black line runs between this
nucleus and the outer black rim in
front; but an additional spot appears




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210 PSYCHE. [May 18118.
on each side above on the first abdorn-
inal segment, a large, finely black-
rimmed, rounded, orange spot seated at
the posterior incisure on a fine black
line which enlarges where the spot
touches it; the two series of small
abdominal spots have become distinctly
turquoise.
In Heraclides cres-fihonfes (Fig. 5)
the young larva is provided with ex-
ceptionally large tubercles, which are
largest at the two extremities, ancl
especially on the first thoracic segment, ancl these are all thickly beset with
bristles ; the body is largest in front but scarcely tumid ; the colors are very dark brown, more or less mottled, with a
distinct white saddle ancl lighter ex-
tremities. Excepting that the front
portion of the body is a little tumid,
and that the tubercles become relatively less important, there is no change in
the next two stages. In the fourth
stage the front part of the body be-
comes distinctly tumid and at the same
time develops an irregular, white, curv- ing lateral band, setting off'the tumidity to better advantage ; the colors and
patterns are otherwise the same as
before, but the tubercles have become
lenticles, and around them have clus-
tered rings of brighter color, by which
the body is much mottled. No further
change is made in the final stage except- ing that the colors are more varied, the whites have become more of R cream
color, and the mottling is more notice-
able, partly from the larger size ; in
general the disposition of the mark-
ings is much as in the newly born
caterpillar.
In Pafitio asfyanax (Fig'. 6), finally,
we have at birth a jet black caterpillar with a white saddle across the middle,
and occasionally a white fleck or two
in front of it; the body is cylindrical
or nearly so, but the thorax shows a
slight tumidity ; it is tuberculate, with conical tubercles, beset with bristles ; there is little inequality in the length of the tubercles, but those on the side of
the body are dull orange. In the sec-
ond and third stages we have a repeti-
tion of the same features in color, form and tubercles ; the orange, however,
becomes a little more vivid. In the
fourth stage, too, the dark tubercles
still remain but are relatively less im- portant, and have at their anterior base a yellow or orange spot; while in the
place of the orange tubercles are
orange lenticles, and these and the
other orange spots break what would
otherwise be a broad, black, transverse
band in the middle of each segment;
for now the body has become green
and is transversely striped with black
in the middle and (more narrowly) at
the front edge of each segment, and no
sign whatever of the saddle remains ;
the form at the same time becomes
more completely cylindrical, but the
body tapers in front. In ihc last stage
this general style of ornamentation and
of form is kept, but the tubercles and
lenticlcs altogether disappear. ,
DATE OF ISSL'E OF LAST NUMBER OF was mailed 011 the morning of the last day of Ps~cu~..-The last, April, number of Psyche the preceding month, as is onr custom.



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