LEELO ST KAT IONS TOg
NORTH AMERICAN
PITCHERPLANTS
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MARY VAUX WALCOTT
DESCRIPTIONS AND NOTES ON DISTRIBUTION
By EDGAR T. WHERRY
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NOTES ON INSECT ASSOCIATES
By FRANK MORTON JONES
PUBLISHED BY THE
SMITHSONIAN INSTITUTION
WASHINGTON, D.C.
1935
CONTENTS
a os
Foreword
Hlustrations and Descriptions of Pitcherplants
1. California Pitcherplant. Chrysamphora californica (TorRREY ) GREENE
2. Green Pitcherplant. Sarracenia oreophila (KEARNEY) WHERRY
3. Pale Pitcherplant. Sarracenia sledgec MACFARLANE
4. Yellow Pitcherplant (Trumpetleaf). Sarracenia flava LINNAEUS
. Red Pitcherplant. Sarracenia jonesit WHERRY
ON
Whitetop Pitcherplant (Drummond Pitcherplant). Sarracenia drummondii Croom
7. Sweet Pitcherplant. Sarracenia rubra WALTER
8. Hooded Pitcherplant. Sarracenia minor WALTER
9. Parrot Pitcherplant. Sarracenia psittacina Michaux
to. Southern Pitcherplant. Sarracenia purpurea venosa (RAFINESQUE) WHERRY
ti. Northern Pitcherplant. Svrracenia purpurea gibbosa (RAFINESQUE) WHERRY
12. Catesby Pitcherplant. » Sarracenia catesbaei ELLIOTT
13. Swrracenta drummondii x rubra
14. Sarracenia rubra x purpurea venosa
15. Sarracenta minor x psittacina
Distribution of the North American Pitcherplants, by Edgar T. Wherry Pages 1-23
Pitcherplants and Their Insect Associates, by Frank Morton Jones Pages 25-33
Bibliography Page 34
FOREWORD
HE STUDENT of wildflowers encounters many forms that are of
unusual interest for one reason or another, but next to the orchids,
probably the most spectacular are the members of the family of
pitcherplants, comprising only fifteen species in the United States and
Canada. Their beautiful coloring and strange mode of growth alone
would make them outstanding among wildflowers; add to this the
amazing association with insect life, wherein insects are trapped in the
pitchers and digested by the plants, and their strong appeal to the curi-
osity and interest is easy to understand.
The collection of pitcherplant sketches here gathered together 1s the
result of several years work. Eight of them were published in the
writer's “North American Wild Flowers”; these, with the others, mostly
new forms recently collected, comprise all the known members of the
family that are native in North America. All occur east of the Rocky
Mountains, except the California pitcherplant, native in northern Calt-
fornia and southern Oregon. Four species are known from Guiana.
The plants grow in acid soil in peat bogs and savannahs, mainly along
the Atlantic Coastal Plain at low altitudes. They range from the southern
United States bordering the Gulf of Mexico and in the lower Mississippi
Valley and northward up the Atlantic Coast into Labrador. In Canada
they are found as far west as the Athabasca valley.
With proper care most of them can easily be grown in a cool green-
house. They should be planted in a mixture of peat and sand in a pot
placed within another pot of two inches greater diameter. The space
between should be filled with sphagnum moss, which must be kept
moist. Rainwater or other soft water should be used.
The illustrations show the striking coloration of the flowers of the
various species of pitcherplants. The petals of some of the varieties last
but a short time, but after they drop off, the curious umbrellas which
are left on the stem are in some species also brilliantly colored. The
fascinating mechanism of the pitchers, or insect traps, are described in
detail in Dr. Jones’ article which forms a part of this publication, but
to illustrate the unusual features of these plants | may mention one
strange adaptation. In the hooded pitcherplant, the pitchers are darkened
by their arching tops, and to introduce sufficient light to entice insects
into the pitchers, the yellow-green tissue of the walls contains a number
of white translucent patches which serve as windows.
Many of the plants were brought into bloom by Dr. Frederick V.
Coville in the greenhouses of the Department of Agriculture in Wash-
ington. To him, and to Dr. Wherry and Dr. Jones, who have contributed
the articles on specific phases of the study of pitcherplants, I extend my
sincere thanks, as I do also to those other friends who have gathered
the specimens that I have sketched.
MARY VAUX WALCOTT
CALIPORNIAS PITGHERPREANT
Chrysamphora californica (Torrey) Greene
Although California pitcherplant is often called Darlingtonia, that
name 1s not acceptable under the standard rules of botanical nomen-
clature, since it had previously been used for an entirely different
plant. The name suggested by Greene to replace it, Chrysamphora,
comes from the Greek words for “golden pitcher.” The genus, which
comprises but a single species, was discovered in 1842, near Mount
Shasta, California, by members of the Wilkes Exploring Expedition.
Nectar is secreted on the concave upper surface of the fishtail-
shaped appendage of the pitcherleaf, and insects alight there to feed
upon it. Following along the curving channel, they unwittingly
enter the orifice and fall to the bottom of the hollow. Their contact
with the walls stimulates the secretion of water, in which they are
drowned. So far as known, this pitcherplant produces no digestive
ferment but obtains its nourishment from the materials liberated by
bacterial decomposition of the dead insects.
The plant sketched came from the mountains of northern Cali-
fornia, where the species is locally abundant.
PLATE I
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GREEN PITCHERPLANT
Sarracenia oreophila (Kearney) Wherry
So far as known, green pitcherplant was first collected about 1875
by Dr. H. M. Neisler in Taylor County, Georgia. He recognized that
it differed from the widespread Swrracenia flava in that it develops
short, flat leaves in addition to the hollow pitchers, and also in the
absence of disagreeable odor from its flowers. Specimens were sent
to Asa Gray and to John Torrey for naming, but they minimized the
differences and failed to consider its possible distinctness. Botanists
who found it subsequently in the mountains of Alabama classed it
as a variety or relative of Sarracenia flava. That it deserves full species
rank was pointed out by Dr. Edgar T. Wherry in 1933.
The presence of flat leaves and the greenish color of the petals
show it to be a primitive pitcherplant, and it may represent the an-
cestor of all the others.
Clumps collected by Dr. Wherry in 1932 near Center, Cherokee
County, Alabama, were brought into bloom the following spring in
the greenhouses of Louis Burk at Latham Park near Philadelphia.
The sketch here reproduced was made from one of these.
PLATE 2
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PALE PITCHERPLANT
Sarracenia sledgez Mactarlane
Although collected by Drummond in Louisiana as early as 1832,
pale pitcherplant was not correctly interpreted for more than
seventy years. At first it was confused with Svrracenia flava, a species
that occurs farther east, and later it was thought to represent one
that had been collected by Elliott in South Carolina and named
Sarracenia catesbaei. Then, in 1904, Dr.J.M. Macfarlane discovered that
the plant to which Elliott had applied the latter name represented a
hybrid between two species, so that a new name was needed for the
pale pitcherplant. Finally, in 1907, Macfarlane named it Sarracenia
sledge 1n honor of Dr. W. H. Sledge, of Mobile, who had sent him
specimens and living plants to enable him to study and describe its
features.
Although closely related to, and presumably a direct descendant
of, the green pitcherplant, the present species differs in the absence
of short flat leaves and in the greater delicacy and creamy color of
the petals. The specimen sketched was grown in the United States
Department of Agriculture greenhouses by Dr. Frederick V. Coville
from roots sent from Mobile, Alabama.
PLATE 3
YELLOW PITCHERPLANT (Trumpetleaf )
Sarracenia flava Linnaeus
The conspicuous yellow pitcherplant was probably seen by many
early explorers of the southeastern United States, but it was first fully
described by Catesby in 1731 under the name “‘Sarracena foltis long-
ioribus & angustioribus”. Although his figure was rather crudely
drawn and has been thought by some to represent other species
nevertheless it agrees 1n all essential respects with the yellow pitcher-
plant. In assigning binomials to all known plants in 1753, Linnaeus
selected the color as its most characteristic feature and accordingly
named it Sarracenia flava.
Like the pale pitcherplant, the present species is to be regarded as a
descendant of the green pitcherplant of the Alabama mountains. It
differs in having conspicuously reflexed hood margins and decidedly
ill-scented flowers with large, delicate, bright yellow petals. Its foliage
varies considerably in coloring, being often veined or blotched with
purple. In the specimen here figured, however, the purple pigmen-
tation was developed scarcely at all. It was grown by Dr. Coville in
the Department of Agriculture greenhouses from roots received
from North Carolina.
PLATE 4
~- MV W
RED PITCHERPLANT
Sarracenia jonesit Wherry
The red pitcherplant was for many years confused with other
species. It was first collected, about 1850, by Rugelin the North Caro-
lina mountains, but because of its red flowers was assumed to repre-
sent Sarracenia rubra Walter. In 1929 Dr. Wherry pointed out its
distinctness from that plant and named it in honor of Dr. Frank
Morton Jones, who had carried on important studies on the relations
of insects to pitcherplants.
The pitchers of the present species are so similar in size and shape
to those of the green pitcherplant that there can be no doubt of the
close relationship of the two. They differ, however, in flower charac-
ters, the one here under discussion being sweet-scented and having
large petals of an intense red color, features that represent a decided
evolutionary advance.
After the distinctness of this plant was recognized, Dr. Coville
obtained roots from the North Carolina mountains and grew it in
the Department of Agriculture greenhouses.
PLATE 5
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WHITETOP PITCHERPLANT
(Drummond Pitcherplant)
Sarracenia drummondii Croom
Whitetop pitcherplant, the most striking of all the eastern species,
was apparently discovered by William Bartram in 1775, but he
failed to describe it correctly, having confused two species. It was
again found by the French explorer Robin and was regarded by him
as a species of Arum. Recognizing its true relationship, Rafinesque
named it Sarracenia leucophylla, and this name has priority over that
assigned to it by Croom. Because Rafinesque’s description was inade-
quate, however, most botanists use the later name.
The flowers of this species are similar to those of Sarracenia jonesii,
presumably its ancestor, although the red coloration is even more
intense. Further evolutionary advance is shown by the leaves, which
are taller and, when mote matute, more brilliantly colored. The hood
and upper part of the tube are white, with broad veins that are
green when the leaf first develops, but later turn more or less red.
The illustration represents a specimen grown by Dr. Coville from
roots sent from Alabama.
PLATE 6
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SWEET PITCHERPLANT
Sarracenia rubra Walter
One of the pitcherplants discovered by Walter and first described
in his Flora Caroliniana in 1788 was the inconspicuous sweet pitcher-
plant. Not only are its leaves and flowers smaller than those of most
other members of the genus, but it 1s also more delicate and more easily
injured by external influences such as late frost, severe drought, and
attacks by parasites. There 1s, however, one attractive feature in which
it surpasses all the others, namely, the exceedingly sweet odor of its
flowers, to which the common name refers. This fragrance closely re-
sembles that of grape blossoms, but also suggests crushed raspberries.
This species, like the whitetop pitcherplant, shows evidence of
being a descendant of Swrracenia jonesiz, but the changes were in the
opposite direction. Instead of an increase in stature and in complexity
of color pattern, the present species shows diminution in these re-
spects, and its fragrance seems to be the only feature in which it excels
its presumable ancestor.
The specimen painted was grown in the Department of Agricul-
ture greenhouses, having originally come from South Carolina.
PLATE 7
M V W
HOODED PITCHERPLANT
Sarracenia minor Walter
The hooded pitcherplant was first described by Walter in 1788
and given the name here used. Michaux discovered it independently,
and named it Sarracenia variolaris, but as this name was published
some years later, the rules require its rejection. It varies greatly in
stature, being sometimes but a few inches in height, when the name
minor 1s appropriate. In most of the plants the pitchers reach a length
of one to two feet, but in the Okefinokee Swamp in southern Georgia
a variety or related species grows to a height of nearly four feet.
The yellow petal color suggests that this species is a direct descen-
dant of Sarracenia oreophila, although the arching hood that excludes
tain water and the translucent membranes that permit light to enter
the pitcher represent evolutionary advances, indicating the former
existence of intermediates which have since become extinct.
This species does not thrive as well as some of the others under
greenhouse conditions. The sketch was made from plants collected
near Beaufort, South Carolina.
PLATE 8
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PARROT PITCHERPLANT
Sarracenia psittacina Michaux
The diminutive parrot pitcherplant is reported to have been ob-
served as early as 1766, but was not described until 1803. Michaux
stated that it occurred southward from Augusta, Georgia, but in
recent years it has not been found within fifty miles of that city.
The peculiar features of this species may well have originated
from the continued operation of the evolutionary trends which led
to the development of Svrracenia minor from a primitive ancestor.
The down-arching of the hood over the pitcher continued to the
point of union with the walls, leaving only a small lateral orifice.
The pitchers shifted to a decumbent position, enabling water to enter
them during flooding of the meadows in which the plant grows.
The flower parts became suffused with red pigment, although the
petals still exhibit an underlying yellow hue like that of the presum-
able ancestor, the hooded pitcherplant.
The specimen sketched was grown in the greenhouses of the
Department of Agriculture in Washington.
PLATE 9
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SOUTHERN PIIGHERPLANT
Sarracenia purpurea venosa (Rafinesque) Wherry
Specimens of southern pitcherplant must have been sent to Eng-
land in early Colonial times, for it was figured by Plukenet in 1705
under the name “Bucanephyllon americanum.” The first colored plate
of it was published by Catesby in 1731. Linnaeus failed to separate
it from its more northern relative, and in his Species Plantarum of
1753 he grouped them together under Sarracenia purpurea. In 1840
Rafinesque recognized its distinctness, and named it “Sarazina venosa.”
It intergrades too much with the northern pitcherplant to be main-
tained as a distinct species, however, and in 1933, Dr. Wherry classified
it as a subspecies, under the name heading this page. It differs from
its northern relative in having a broader pitcher with more ample
hood, often pubescent on the outside, and paler petals, ranging in
color from light red to rose-pink.
Roots of the southern pitcherplant were sent to the Department
of Agriculture greenhouses from North Carolina in 1931, and the
painting here reproduced was made from one of these when it came
into bloom a few wecks later.
PLATE IO
W
M V
Oo.
NORTHERN PITCHERPLANT
Sarracenia purpurea gibbosa (Rafinesque) Wherry
One of the earliest known figures of a Sarracenia, that published
by Clusius in Historia Plantarum Rariorum in 1601, represented this
subspecies. Linnaeus did not distinguish it from the southern one, but
Rafinesque in 1840 named it “Sarazina gibbosa’. Reasons for inter-
preting it as a subspecies were published by Dr. Wherry in 1933. Its
pitchers are relatively long and narrow, with a rather small hood
behind the orifice, and pubescence only rarely appears on the outer
surface. The petal color is usually of an intense deep red, but a muta-
tion in which the whole plant lacks red pigment, and of which the
petals are bright yellow, appears occasionally. This was named Swr-
racenia heterophylla by Eaton, but is now regarded as deserving at most
only the status of a form.
A related plant, characterized by the presence of elongated rhi-
zomes, has recently been named Sarracenia purpurea stolonifera by Drs.
John M. Macfarlane and D. Walter Steckbeck. It does not differ from
the others in leaves or flowers sufficiently to be included here.
The specimen sketched came from the bogs of eastern Maryland.
PLATE II
I.MV W
CATESBY PITCHERPLANT
x Sarracenia catesbaei Elliott
Most of the species of Sarracenia discussed in this publication are
capable of hybridizing with one another, and the hybrids combine
the characters of the parents in a striking way. The cross most fre-
quently found in nature is that of Sarracenia flava and S. purpurea
venosa, With leaves and petals intermediate in shape and coloring
between the two. For many years this was supposed to be a distinct
species, and it was named by Elliott in honor of Catesby, who pub-
lished the first colored plates of pitcherplants, but its true nature was
pointed out by Macfarlane in 1904.
The specimen sketched came originally from Quincy, Florida, and
was grown for a number of years in the Department of Agriculture
greenhouses.
PLATE 12
M V W
2
Sarracenia drummondii « rubra
This hybrid was produced by Dr. Frederick V. Coville in the
Department of Agriculture greenhouses, the plant having reached
blooming size from seed in three years. In leaf and flower characters
it lies midway between its parents. Some of the plants produce
flowers having the large size and rich coloring of Sarracenia drum-
mondi, with a sweet odor derived from the other parent, Sarracenia
rubra.
PLATE 13
VW
Sarracenia rubra x purpurea Venosa
This is another wild hybrid, which combines the characters of its
parents in a striking way. It was collected in southeastern North
Carolina by Sir Henry Wellcome, and presented by him to the United
States Department of Agriculture.
PLATE 14
M V W
Sarracenia minor x psittacina
This represents a natural hybrid, collected by Dr. Wherry in south-
ern Georgia, where it grew in company with its parents. The leaf
orifice 1s intermediate in size between those of the two parent plants,
and the petal color shows a combination of the yellow of the first
with the red of the second species.
PLATE 15
M V W
DISTRIBUTION OF LHE
NORTH AMERICAN PITCHERPLANTS
BY EDGAR T. WHERRY
Associate Professor of Botany, University of Pennsylvania
The pitcherplant family (Sarraceniaceae) consists of three genera, Sarracenia, Chrysamphora,
and Heliamphora. Nine species of Sarracenia have been recognized thus far, one of them rang-
ing from the Gulf Coast far north into Canada, the others restricted to the southeastern
United States. The genus Chrysamphora, also known as Darlingtonia, is monotypic, its single
species occurring in northern California and southwestern Oregon. One species of Heliam-
phora was described in 1840 and for ninety years remained the only known representative
of the genus, but three more have now been found. These are limited to northern South
America, however, and will not be discussed in this article.
KEY TO THE NORTH AMERICAN PITCHERPLANTS
Pitcher hood bearing a fishtail-shaped appendage; scape bracted; petals bronzy yellow; style
fadiate: 4 a. = ae ee 2 eee Chrysamphora californica
Pitcher hood not Repentoeed: scape Pec ate normally expanded into an umbrella-shaped
SUC Wee ue eee cenen tet. (Ure MGC. sclera G89 an We ae Wis ee oc grocers
Pitchers erect or essentially so.
Pitcher orifice incompletely covered by hood.
Margins of the large hood more or less reflexed.
Hood yellow-green, veined or suffused with red.
Petal-color of a yellow type.
Reflexing of hood margins slight; petal texture firm.
Flat leaves abundant; petals greenish yellow . . S. oreophila
Flat leaves sparse; petals creamy yellow. . . . .S. sledgei
Reflexing conspicuous; petals delicate, yellow. . . . . S. flava
Petal-color ofaredtype . . . ee ee Aa 5. /0000527
Hood white, green- and red-veined; eis fa 2... S. drummondii
Margins of the small hood not reflexed; petals red 2. 2 1)... SS. rubra
Pitcher orifice well covered by hood; petals yellow. . . . . . . . . S. minor
Pitchers decumbent; petals red or exceptionally yellow.
Oritice lateralesmall; hoodclosed = = 5 4 eS pazttacina
Orifice terminal, large; hood open.
Pitcher outline short and broad . «ww wees. .SCOS. purpurea venosa
Pitcher outline long and narrow. . . . . . . .S. «SS. purpurea gibbosa
Data as to the relationships and distribution of the species have been obtained mainly
from studies in the herbaria of the Academy of Natural Sciences of Philadelphia, Canadian
National Museum, Cornell University, Gray Herbarium, New York Botanical Garden,
I
United States National Museum, and University of Pennsylvania, and from the following
publications:
Sarraceniaceae, by John M. Macfarlane. Engler’s Pflanzenreich, vol. 1v. 110, 1908.
The American pitcher-plants, by Roland M. Harper. Journal of the Elisha Mitchell Scientific
Society, vol. 34, p. 110, 1918.
The biochemistry of the American pitcher-plants, by Joseph S. Hepburn, Frank M. Jones, and
Elizabeth Q. St. John. Transactions of the Wagner Free Institute of Science, vol. 11, 1927.
Four articles relating to pitcherplants have previously been published by the writer:
Acidity relations of the Sarracenias. Journal of the Washington Academy of Sciences, vol. 19,
P. 379, 1929. CThe species ranges given in that paper are somewhat modified in the present
one in accordance with data subsequently obtained.)
The geographic relations of Sarracenia purpurea. The Appalachian relative of Sarracenia flava.
Bartonia, vol. 15. p. 2, 1933.
Exploring for plants in the Southeastern States. Scientific Monthly, vol. 38, p. 80, 1934.
As pointed out in the paper by the writer on Sarracenia purpurea, some recently pub-
lished maps of the distribution of the members of the Swrraceniaceae (Die Pflanzenareale,
vol. 3, pt. I, 1931) are not satisfactory, having been constructed from incomplete data for
most of the species. A new set of maps 1s accordingly presented herewith, based on a thor-
ough review of the literature, a cataloging of numerous herbarium records, and extensive
field observations.
The base map shows, in addition to State boundaries, two geologic lines of plant-geo-
graphic significance. The more northern of these represents the limit reached by the last, or
Wisconsin, ice sheet, as mapped by Antevs (Bulletin of the Geological Society of America,
vol. 40, p. 63.1, 1929). The southern line is the fall line, taken from the map of Physiographic
Divisions of the United States, published by Fenneman (Annals of the Association of American
Geographers, vol. 6, p. 19, 1917). Most of the territory enclosed between these lines has been
continuously available for occupancy by plants since Cretaceous time, when the development
of our modern flora began.
On the individual maps, areas where the species is frequent in favorable habitats are
dotted. When the boundaries have been fairly definitely determined, they are marked by
solid lines, and when only approximately known, by dash lines. Presumable migration routes
are indicated by arrows.
Before the individual species are discussed, the geologic relations of the group as a whole
require brief consideration. Physiographic studies indicate that prior to and during the Creta-
ceous much of eastern North America was reduced to a peneplain. The sea then extended
up to what is now the fall line, and for some distance northward and westward from this
boundary the conditions for plant growth were similar to those of our present-day Coastal
Plain. There were vast level areas covered by alluvial sands and clays, traversed by sluggish,
a.
meandering streams, and dotted with bogs and swamps. This was the ancestral home of
many present-day species of plants.
During the Tertiary, uplift of the land took place, and erosion developed the present
topography. Some of the plants adapted themselves to the cooler climate of more elevated
areas and grew there throughout the course of the development of our Blue Ridge and
Appalachian Mountains. Others proved unable to adjust their temperature requirements
and died out from their ancestral regions. Meanwhile, however, the sea was gradually
retreating, leaving land open to occupation by plants, and seeds or other disseminules of
many species found their way down various river valleys and developed colonies on the
newly formed Coastal Plain. Most of the Sarracenias evidently migrated in this manner.
CALIFORNIA PITCHERPLANT
Chrysamphora californica (Torrey) Greene
Though currently believed to be restricted to a few mountain bogs in California and
southern Oregon, a study of the literature and of herbarium records has revealed that California
pitcherplant grows in numerous localities from Placer County, California, where it reaches an
altitude of over 8,000 feet, to Lane County, Oregon, where the writer has collected it at
sea level. It grows in swamps, bogs, and springy places where the reaction 1s usually intensely
acid and the soil temperature probably never exceeds 65° Fahrenheit.
This plant evidently developed, during Cretaceous times, so far west that when the
Tertiary uplifts occurred, its seeds failed to reach the drainage basins of any of the eastern
rivers, and it accordingly did not colonize the Atlantic Coastal Plain. Instead it migrated
westward, and occupied the area which subsequently became the Sierra Nevada and the Coast
Ranges, between latitude 39° and 44° N. All traces of the connecting links between this and
the related genera Heliamphora and Sarracenia were destroyed by the geologic events of
Tertiary times, or by the advances of the ice sheets of the glacial epoch.
33°
English Miles 691-1 Degree
200 soo a. 7
WISCONSIN ICE SHEET
FALL LINE
FIGURE I
Distribution of green pitcherplant, Sarracenia oreophila
GREEN PITCHERPLANT
Sarracenia oreophila (Kearney) Wherry
Green pitcherplant, the most primitive of the eastern species, was apparently first collected
along the inner margin of the coastal plain in Taylor County, Georgia, but it later proved
to occur chiefly in the Appalachian Mountains region of northeastern Alabama. It has been
found thus far in a number of stream valleys in Cherokee, De Kalb, Jackson, and Marshall
Counties, and may be considerably more widespread.* Unlike most species, it grows in allu-
vial sands and gravels on stream banks, rather than in bogs or swamps. The soil reaction,
however, is rather intensely acid.
In Alabama the Cretaceous peneplain was not uplifted high enough above sea level for
the climate to become very much cooler, so that little increase in hardiness was necessary
to enable plants to survive there. The ancestral home of this pitcherplant may accordingly
be inferred to have been essentially where it now occurs. Of all the species, 1t has been the
least successful in colonizing the Coastal Plain, its seeds having apparently reached that
province only after it had become too conservative to spread there.
* While this article was in page proof, and after the map was engraved, an additional station for it was discovered
in Elmore County, in central Alabama.
.
F Pee -
ee Pt)
e e
See 2 Oe,
WISCONSIN. ICE SHEET
FALL LINE
Longitude West 80° from Greenwich
FIGURE 2
Distribution of pale pitcherplant, Sarracenia sledgei
PALE PIICHERPLAN T
Sarracenia sledget Macfarlane
The ancestral home of pale pitcherplant was presumably in what is now the Cumber-
land Plateau of Tennessee, where one or two colonies are reported to survive. It migrated
down the Tennessee and the Mississippi River systems, after they developed. Becoming
colonized on the Coastal Plain, it then spread eastward into Alabama, there approaching
but apparently not intermingling with its eastern relative, Sarracenia flava.
It also spread westward across Louisiana and 1s the only species known to have reached
Texas. The westernmost station from which a specimen has been seen is near Athens,
Henderson County, nearly at longitude 96° W. There are credible records of this pitcher-
plant from a short distance farther west, but, growing as it does in acid swamps and springy
meadows, it is unable to enter the more arid portions of Texas, and reports of its occurrence
there have proved to be erroneous.
The map here reproduced shows the range of this plant as at present known, although
it probably grows farther north in the Mississippi Valley and has merely failed to be
collected by the few botanists who have explored that region.
H 4
N6TON Pp 3B
f s
se Uf 0
0 ~ é iF
eae
” was
Longitude West 80° from Greenwich
WISCONSIN. ICE SHEET
FALL LINE
FIGUR
ee)
Distribution of yellow pitcherplant, Sarracenia flava
YELLOW PITCHERPLANT
Sarracenia flava Linnaeus
The yellow pitcherplant developed farther east than its relative, the pale pitcherplant, and
in the course of the Tertiary uplift and erosion which resulted in the development of the
southern highlands it managed to survive in a number of places in North Carolina. As the sea
gradually withdrew from the old shore line, leaving new land open for occupation by plants,
the seeds of this species traveled down various river systems in North and South Carolina and
Georgia, and started colonies in the Coastal Plain. Lateral spreading from these colonies also
occurred, and the species reached on the one hand, nearly to the Alabama River, and on the
other, to the James River in Virginia.
Like most plants with such a geologic history, this pitcherplant gradually lost its aggres-
siveness, and by middle Tertiary time its colonies apparently ceased to expand further.
Accordingly, although it grows in abundance in moist meadows and depressions in pinelands,
it has never been able to enter lower peninsular Florida, which emerged from the sea only
toward the close of the Tertiary.
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FIGURE 4
Distribution of red pitcherplant, Sarracenia jonesii
IO
RED PITCHERPLANT
Sarracenia jonesit Wherry
Red pitcherplant grows mostly in swamps and meadows underlain by loamy soil of mod-
etate Of sometimes intense acidity. It seems to have developed in the same general region as
Sarracenia flava, but somewhat farther north. When the Tertiary uplift took place, this plant
managed to survive in a small area in Buncombe and Henderson Counties, North Carolina.
Seeds from these colonies never reached rivers flowing into the Atlantic, however, and it
failed to migrate in that direction.
Toward the western end of its ancestral area, on the other hand, these relations were
reversed. The geologic changes exterminated it from this portion of the range, but before that
occutred, seeds reached the headwaters of the Alabama River system, and developed colonies
farther down stream. It managed to get a foothold in the Alabama Piedmont province and,
when the Coastal Plain emerged from the sea, also invaded that region. Some lateral spreading
from the main river valley occurred, so that it migrated a short distance into Florida and
Mississippi, but by mid-Tertiary time it had apparently lost all ability to increase its range
further.
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WISCONSIN. ICE SHEET
FALL LINE
Longitude West 80° from Greenwich
FIGURE 5
Distribution of whitetop pitcherplant, Sarracenia drummondii
9d
WHITETOP PITCHERPLANT
Sarracenia drummondii Croom
The evolutionary changes which resulted in the development of the showy red-flowered
Sarracenia jonesit from a rather inconspicuous green-flowered ancestor did not come to an
end with that species, but continued along several lines. The tendency toward increased size
and coloration reached a culmination in whitetop pitcherplant, the showiest of our species.
The common name selected for it refers to the predominance of white in the hood.
Development of this pitcherplant evidently took place somewhere in the headwaters of
the Alabama River system. The Tertiary mountain-making exterminated it from its ancestral
home, but seeds traveled downstream and soon colonized the Coastal Plain. Spreading laterally
from this river valley, it migrated a short distance westward into Mississippi and somewhat
farther toward the east, into the western extension of Florida. It also formed two isolated
colonies, one in Madison County, Florida, the other in Sumter County, Georgia. Reports of
its occurrence farther northeast seem to be based on misidentification of other species.
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FALL LINE
Longitude West 80° from Greenwich
FIGURE 6
Distribution of sweet pitcherplant, Sarracenia rubra
14
SWEET PITCHERPLANT
Sarracenia rubra Walter
As shown by the accompanying map, sweet pitcherplant occurs mostly near the fall line
in Georgia and South Carolina, although tn North Carolina it extends to the coast. Its north-
ernmost known station 1s at Southern Pines, in Moore County. There is also an apparently
isolated area in western Florida.
This distribution indicates that the species originated, as a descendant of Swrracenia jonesii,
somewhere on the headwaters of the Santee River system. Being very sensitive to cold, it
was exterminated in its ancestral home by the climatic changes accompanying the Tertiary
uplift, but seeds meanwhile drifted downstream and colonized the Coastal Plain. Its devel-
opment chiefly near the fall line indicates its early arrival after the retreat of the sea, but it
soon lost its aggressiveness and only locally reached the outer part of the Coastal Plain.
The favorite habitat of the sweet pitcherplant is a moist, grassy thicket near the margin
of a swamp, although it can grow also in dense shade. The soil is usually peaty and in-
tensely acid.
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FIGURE 7
Distribution of hooded pitcherplant, Sarracenia minor
16
HOODED PITCHERPLANT
Sarracenia minor Walter
Peninsular Florida emerged from the sea only toward the close of the Tertiary age, and
as by that time most of the Sarracenias had apparently lost their ability to colonize new
territory, they are not to be looked for in that region. The one exception to this rule is the
hooded pitcherplant, which extends far southward over the State, being reported even in
Palm Beach County, at latitude 26° N. In other directions its range is more restricted, how-
ever; it is the only species which has, so far as known, failed to reach the State of Alabama.
It is frequent in southern Georgia, but gradually diminishes in abundance northeastward
and barely enters North Carolina.
Such a distribution indicates that the species originated on that part of the Cretaceous
peneplain which has since become the Georgia Piedmont. Although unable to survive the
geologic changes there, its seeds found their way down the Altamaha River system, and
colonized the Coastal Plain. It thrives best in moist meadows or open pinelands, underlain
by loamy but intensely acid soil, and as such habitats are common, it has attained a wide range.
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WISCONSIN. ICF SHEET
FALL LINE
Longitude West 80° from Greenwich
FIGURE 8
Distribution of parrot pitcherplant, Sarracenia psittacina
18
PAR KO TAPIT CE ER PEN
Sarracenia psittacina Michaux
The distribution indicated on the accompanying map shows that the parrot pitcherplant
originated at some point in the ancient peneplain near what is now the northwestern corner
of Georgia. From this region it disappeared as a result of the geologic and climatic changes,
but its seeds found their way down both the Alabama and Chattahoochee Valleys. The
colonies thereby formed on the Coastal Plain expanded laterally, reaching the vicinity of
New Orleans on the west and the coast of Georgia on the east. Search for it near Augusta,
Georgia, where it was stated by Michaux to occur, has proved unsuccessful, the northeastern-
most colony thus far found lying 10 miles southwest of Millen, in Jenkins County.
Like most of the others, this species apparently lost the ability to expand its range farther
before the end of the Tertiary. It thrives best in low meadows subject to frequent inunda-
tion by acid waters from nearby swamps, but in |spite of the abundance of such habitats
which developed in peninsular Florida after it emerged from the sea, the plant has never
succeeded in entering that region.
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WISCONSIN. ICE SHEET
FALL LINE
90° 85° Longitude West 80° from Greenwich eo 70° 65°
FIGURE 9
Distribution of southern pitcherplant, Sarracenia purpurea venosa
2O
SOUTHERN PITCHERPLANT
Sarracenia purpurea venosa (Rafinesque) Wherry
Southern pitcherplant occurs in swamps, bogs, and wet meadows in nearly every part of
the State of North Carolina. It probably originated in the region now constituting Henderson
and adjacent counties, but when this territory was uplifted, the immediate ancestors of the
plant were exterminated. There can be little doubt, however, that it is a remote descendant
from Sarracenia jonesiit, which has managed to survive in the same general region, for the
flowers of the two are almost identical, in spite of the dissimilar leaf shape.
In the course of time its seeds were transported down several of the eastward-flowing
tivers, forming colonies on the Piedmont and ultimately on the newly emerging Coastal Plain.
Some seeds also found their way down the Chattahoochee River system, and an extensive
series of colonies developed near the coast on either side of this valley. In addition, unlike other
species, it migrated from northeastern North Carolina to southern New Jersey, over a strip of
land which apparently connected these States during Tertiary and early glacial times.
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Distribution of northern pitcherplant, Swrracenia purpurea gibbosa
22
NORTHERN PITCHERPLANT
Sarracenia purpurea gibbosa (Rafinesque) Wherry
Northern pitcherplant ranges from Maryland, Delaware, and New Jersey northward over
a vast territory in this country and Canada. The geographic relations, together with the
presence of intermediates between the northern and southern subspecies in southern New
Jersey, indicate that the northern one originated in that region. Evidently the southern an-
cestor, after arriving in New Jersey, became variable, and gave rise to descendants differing
more or less in morphological and physiological characters. Most of these, lacking ability to
extend their ranges, have remained where they originated. One, however, became highly
ageressive, and as it also differs in pitcher shape, it is classed as a distinct subspecies.
During the ice advances of the glacial epoch this pitcherplant was of course unable to
migrate northward, and merely spread a short distance into Maryland and southern Pennsyl-
vania, but after the retreat of the last ice sheet it soon occupied the newly developed bogs,
and even managed to reach sub-Arctic Canada.
PITCHERPLANTS AND THEIR INSECT ASSOCIATES
BY FRANK MORTON JONES
Wilmington, Delaware
VICTIMS OF THE PLANTS
That the pitcherplants are “intended” as insect traps—that their capture of insects is not
an accident of evolution and of no real significance to the plants—is attested by a mass of
evidence which in its entirety is overwhelming. Some of that evidence will be presented here.
The pitchered leaves, so flowerlike in coloration and shape that the nonbotanical observer
usually mistakes them for true flowers and often compares them with jack-in-the-pulpit or
with the spathes of the skunkcabbage, bear out an interpretation that their function, like
that of flowers, is the attraction of insects. Confirming that interpretation, these flowerlike
pitchers at their more active period diffuse a fruity or honeylike fragrance from a nectar
secretion containing fruit sugar, whose attraction for insects is often visibly evidenced by
columns of ants climbing their walls and feeding in rows upon the exuding nectar, or by wasps,
bees, butterflies, and moths flying from pitcher to pitcher, alighting and feeding upon the
nectar globules that stud their tops. The nectar glands are so distributed that they form
attractive pathways for the visiting insects, which are further guided by bristly hairs or by
a fine pile, so directed that a feeding insect is unconsciously urged toward and into the pitcher's
mouth. Within the mouth of the pitcher the surface texture changes to one of extreme
smoothness, as a result of which the visiting insect is precipitated to the bottom of the
pitcher. From this detentive area escape is rendered difficult by steep and narrow walls,
smooth or lined with downward-directed hairs; often, too, the falling insect is plunged into
a liquid which fills the lower portion of the pitcher's tube and which has the property of
quickly terminating the struggles of an entrapped insect, so that within a few seconds all
efforts toward escape cease, and rarely does even the strongest insect succeed in gnawing its
way out through the pitcher's walls.
This pitcher liquid, originally a natural secretion of the plant, but eventually more or
less contaminated and diluted from outside, is thus an important part of the insect trap. Its
continued effectiveness is enhanced by its rapid increase in volume in response to the presence
of nutrient matter; that is, the liquid increases in quantity as insects are captured, and experi-
mentally, to a surprising degree, when milk or raw meat, for example, is introduced into a
pitcher. In most species the pitcher liquor contains a proteolytic enzyme, similar in its
properties to the digestive enzymes of the mammalian stomach; steeped in this stupefying
and digestive liquid, the softer parts of the entrapped insects are quickly dissolved. Absorption
by the plant from the fluid contents of the pitcher has been demonstrated by careful
experiment and chemical study.
Added to the cumulative evidence of these characters of the pitcherplants and other
a
characters possessed by individual species among them but not common to the group—char-
acters which taken together are susceptible of the single interpretation that they are adap-
tations or adjustments for the capture and utilization of insects by the plants—there is the
further evidence that as insect traps they are astonishingly eftective—that as traps, they work.
Of all our pitcherplants, perhaps Sarracenia purpurea and Sarracenia psittacina are com-
paratively the least successful as insect traps. The sphagnum-embedded pitchers of purpurea,
however, functioning as water-filled pitfalls for attracted insects, or for those casually wander-
ing by, usually contain a few insects in their lower tubes, and sometimes they are crammed
with the bodies of beetles, crickets, or grasshoppers, when these insects abound. Although
the narrow-entranced pitchers of pséttacina, may reveal little evidence, beyond an occasional
spider, of numerous captures, they are sometimes (and especially after the subsidence of
temporary floodwaters which have covered low-growing plants) literally stuffed with the
polished bodies of water beetles, held rigidly by the long elastic hairs which line the
narrow tubes.
Although the hooded pitchers of Sarracenia minor, and the slender grouped pitchers of
S. rubra capture a wide range of insect species, yet these plants seem to specialize in the cap-
ture of ants, big and little, and their pitchers are often packed for several inches of their
length with the bodies of hundreds of ants, sometimes of a single abundant species from
some adjacent anthill.
Of the larger pitcherplants such as S. flava, sledgei, and drummondii, only those who have
walked through expanses of their tall pitchers, lifting their hoods and peering in at their
mote recent captures, occasionally splitting open a mature pitcher and investigating its varied
contents, can appreciate the enormous number and variety of these captures, even in sur-
roundings which are not otherwise obviously rich in insect life. Here the entomologist may
find many species: beetles, large and small, bees, wasps, parasitic Hymenoptera, moths, flies,
grasshoppers, even such actively flying insects as butterflies and dragonflies, and including
species whose local presence he may not have even suspected. Spiders, living and dead, are
frequent occupants. Not rarely, little green tree toads sit by day within the mouths of the
larger pitchers; but their bones, and those of the slender “chameleon” lizards, embedded among
the fragmentary insect remains below, bear witness to the fact that even these vertebrates
are not always successful in escaping the trap when once they have ventured within the
pitcher's mouth.
Similarly, the pitchers of Chrysamphora (Darlingtonia), ftom the first hours of the opening
of their cobralike hoods, begin to capture insects, until their great tubes are stuffed with
insect remains, which in variety form almost a cross-section of the insect fauna of the plant
habitat. This western species seems to lack the digestive enzyme of Sarracenia, and soon its
accumulated insect captures are converted into an ill-smelling mass, even contaminating the
air of their mountain bogs with the odor of decay.
The pitcherplants are real insect traps.
26
POLLINIZERS
Pitcherplants, by their trap structure almost unique in their relations to the insect world,
do not confine those relationships to the status of trap and victim. The flowers of Sarracenia
are dependent upon insects for their pollination, and they are adjusted structurally and phys-
iologically to encourage, if not to enforce, cross-fertilization by insect agency.
For example, the globular flowerbud of Sarracenia flava, in March or April, pushing up
rapidly from its fleshy rootstock, is at first held upright upon its stem; but before the swell-
ing bud has lost its globular form, it makes a complete reversal of position, so that when
the petals expand the flower opens downward. The promptly shed pollen falls into the
concavity of the umbrella-shaped style which closes the flower below. The stigmatic points
are entirely outside the dome-shaped cavity formed by the petals and having the style as
its floor; for they are located, one at each of the five projecting points of the umbrella. A
visiting insect, alighting on the shelflike base of a petal, turns either right or left to an open-
ing between two adjacent petals and under one of these points, against which (if the insect
should be of suitable size) it scrapes its pollen-dusted back as it enters. On departure, the
insect may leave the flower by the same route; but especially in the more loosely textured
flowers of other species, escape is readily and more frequently made at some other point
around the edge of the umbrella.
Though the pollen is shed promptly after the opening of the flower, nectar continues
to be secreted and insects attracted for many days, even for several wecks, after that event;
and a further change in the position of the flower (this time toward the vertical) commences
within a day or two of its opening, thus tending to spill out the pollen and to permit visiting
insects to avoid intimate contact with that which may have accumulated in the concavity of
the style. These phenomena bear out the interpretation that in Sarracenia the fall of the pollen
is antecedent to the receptivity of the stigmas of an individual flower, and that fertilization
is effected by an entering insect which has received its pollen-coating in another flower.
Ants, bees, and pollen-eating beetles are all frequent visitors to the flowers of Sarracenia.
Among their visitors, thick-bodied bumblebees can scarcely force an entrance between the
petals without scraping one of the stigmatic points; the Sarracenia flies frequently crowd into
the blossoms, apparently more for shelter at night and in bad weather than in search of food;
honeybees are regular visitors, and they more nearly fit the entrances than do the smaller wild
bees of several species, which, nevertheless, are usually the more numerous among the insect
visitors and which are probably the insects most concerned in effecting fertilization. Thus
these flowets, attractive to a considerable range of insect species, are not dependent upon any
one insect for the transference of their pollen from flower to flower.
PEANI-EATING INSECTS
The most familiar plant-insect relation is that existing between a foodplant and the insect
which attacks it. Several insect species have the Sarracenias as their preferred or their sole food,
=,
under conditions which for them eliminate the danger of the plant’s trap structure, which is
so generally fatal to other insects. The flowers, and seasonally later the seed vessels of Sarracenia,
in all its species and apparently throughout its geographical distribution, are eaten by small
greenish caterpillars with black heads, which, having completed their work of destruction,
spin flimsy cocoons among the refuse of their feeding or for pupation sometimes tunnel into
the hollow flower stem, and finally emerge as small dark-colored moths (Olethreutes daeckeana
or O. hebesana), to continue in turn this life cycle of destruction. Being thus concerned only
with parts of the plant which do not bring them into contact with the pitcher's trap, with-
out danger to themselves they sometimes destroy a very considerable percentage of that seed
which has been made possible by the visits of another set of insects, the pollinizers.
The fleshy, starch-filled rhizomes of all species of Sarracenia offer a safe food supply to
another and much larger insect, a pale boring caterpillar which attains a length of nearly two
inches. It tunnels the rootstocks, pouring out on the ground about the plant many corky
pellets, ferruginous in color, thus giving a ready clue to its destructive presence. Sometimes
these pellets are built up into a turretlike structure, resembling in miniature the mud turrets
of the crayfish. The parent moth of the Sarracenia root-borer (Papaipema appassionata) is a
beautiful creature, maroon-red and yellow in color, and was long so rare that only a single
specimen was known in all the museums of the world; but since the discovery of its pitcher-
plant habitat, entomologists have been able to procure specimens in any desired number. The
moth emerges in the early autumn and deposits its seedlike eggs; in the spring the eggs hatch
as little boring caterpillars, which tunnel their way into the rootstock, with an entrance at the
terminal bud. Like the related and too familiar iris borer, this insect sometimes survives the
transportation of the plants even to foreign countries, destroying plants which may have been
procured at great trouble and expense.
Because of its habits, the Sarracenia root-borer does not of necessity come into conflict with
the pitcher's trap. There are, however, three other insects having Sarracenia as their obligatory
foodplant (for they will eat nothing else), which are concerned, not with blossom or seed or
root, but with the pitchers themselves. They are the three pitcherplant moths, which through-
out their lives, from egg to adult, are in intimate contact with the pitchers, at every turn and
change of their varied existence utilizing these dangerous structures to their own advantage.
The pitcherplant moth sits in a pitcher, head up, throughout the day. If disturbed, it backs
further down the narrowing tube; and if compelled to fly out, it flies rapidly to another
pitcher, near or far, alights outside, and runs in over the rim, where once more it assumes
the habitual head-up position upon the pitcher's inner wall. This ability to enter and leave
the pitcher trap seems to consist simply in knowing how; for the moths do not exhibit any
marked structural adaptation to assist them. The three pitcherplant moths all belong to the
same genus, Exyra; and although each Exyra species is able to survive for a time in asso-
ciation with any Sarracenia species, yet they do exhibit some habitual preferences among
these plants.
28
One of these Exyras, rolandiana, 1s consistently associated with Sarracenia purpurea through-
out much of that plant’s wide geographical range. Wine-ted, yellow, and smoky purple in
color, this moth matches well the highly colored walls of the open-topped pitcher in which
it sits by day. The other two Exyras, semicrocea and ridingsii, are not found north of Virginia;
they retain their (probably) ancestral colors of dull yellow contrasted with smoky black, and
they are habitually associated with those other Sarracenias whose hooded or lid-covered
pitchers offer better concealment from outside view, so that color for these moths may not
have the same significance.
The moths lay their minute eggs on the inner walls of the pitchers. Hatching from
these, the little caterpillars, throughout life and by various devices, maintain for themselves
closed feeding chambers, in which they may live with some degree of concealment and pro-
tection from external foes. This they accomplish by closing the mouth of the pitcher above,
and by feeding below only on the inner layers of the pitcher's wall, until this is reduced to
a bladderlike thinness, the caterpiller as it feeds sealing all accidental holes and fissures with
silk. To close the pitcher’s mouth, one of several alternative methods 1s employed. The more
prevalent of these is to spin a fine, close, and almost opaque web across the throat of the
pitcher; or in a young and tender pitcher, a tightly closed chamber ts often attained by eat-
ing a threadlike groove encircling the upper portion, above which groove the pitcher dies,
dries, and hardens, thus effectually and permanently closing the pitcher at the top. One or
the other of these methods is usually followed, either to obtain a closed feeding chamber
with its added safety, to provide a retreat for pupation, or in the autumn to prepare a hiber-
naculum for the young larva, which must survive the winter in that concealment; for thus
all the Exyras pass the winter, each ensconced in a pitcher of Sarracenia.
The young larva of seméicrocea, when it finds itself in the narrow-throated pitcher of
psittacina, vaties this method by closing the pitcher's constricted throat with a dense wad
of chewed vegetable fragments and silk, ensuring for itself a watertight compartment for
the winter; and rédingsiz, in its larger pitcher, constructs a vaulted chamber among the refuse
of its own feeding.
When about to pupate in a web-ceiled pitcher, the caterpiller of Exyra makes no provi-
sion for the exit of the moth, which by slight pressure from within 1s able to force a way
through the thin web; but in the narrow-throated pitchers of pséttacina, or in the purpose-
fully collapsed pitchers of flava, the larva, before spinning its cocoon, cuts a small round hole
in the pitcher's wall as a provision for the emergence of the moth to be, which would
otherwise be unable to find or force its way out to the open air.
These and other adjustments of Exyra to life within the pitchers of Sarracenia are in the
main psychical rather than structural; but in various stages of their existence structural modi-
fications, too, seem to relate to life within the pitchers. In illustration, along the bodies of
the caterpillars of the two Exyras which live in the narrow-tubed southern Sarracenias are
several strongly spined elbowlike projections which hold them out from close contact with
a
the walls of the pitchers and prevent these larvae from being wedged fast in the tapering
cavities they inhabit; whereas the caterpillar of rolandiana, living in the squat, open-topped
pitchers of purpurea, does not so greatly need nor does it possess these appendages.
Thus instinctive and structural adjustments make possible a relationship between insect
and insect-eating plant, entirely to the plant's disadvantage; and the conclusion seems inevitable,
that although the plant has brought its trap structure to such perfection that few insects may
escape it, yet the pitcherplant moths, in their evolution, have met these dangerous conditions
and have actually turned them to their own advantage.
PITCHER. ROBBERS
In nature, the usual response to any concentration of potential food supply is a flocking in
of claimants for that food; so that it is to be anticipated that the store of animal matter
accumulated in the pitchers of Sarracenia, when once their traps become operative, should
attract other animals, and that some of these should evolve methods of eluding the trap and
of securing for themselves a portion of that food. These pitcher robbers are of a number of
species, and some of them are so permanently adjusted to life as associates of the pitcherplants
that they have lost the ability to survive under any other conditions. For example, no sooner
have captured insects begun to accumulate in the pitchers than among the dead and dying
insects we may usually find one or several living whitish maggots, which in fluid-filled pitchers
wriggle their way up to each fresh capture and commence to feed upon it as it floats on the
surface. The larger of these maggots are the young of the Sarracenia flies, genus Swrcophaga,
with at least six species having this habit and habitat. As young maggots, they are deposited
within the pitchers mouth by the parent fly. Feeding upon its captures until they have
attained larval maturity and a length of about three-quarters of an inch, they then usually
leave the pitcher and change to brown puparia in the sand or moss at the base of the plant.
From these puparia in due course emerge adult flies, which continue the life cycle as before.
These insects, throughout their stages, seem to possess no structural adaptations to fit
them for life in their dangerous habitat; but like the pitcherplant moths, they know their
way in and out of the pitchers and rarely fall victim to the trap. They confer no benefit
upon the plant in compensation for their robbery of it, unless the habit of the flies of ctowd-
ing into the flowers at night and on stormy days may give them status as pollinizers, to which
office their appropriate size and their bristly integument seem to fit them. One remarkable
character of these larvae may have originated as a needed defense, for like the intestinal worms
of mammals, these fly larvae contain an anti-enzyme which inhibits digestion, so perhaps
their ability to spend their lives, bathed in the digestive fluids of the pitchers, is attributable
to this quality as a necessary defensive character.
Sarcophaga larvae are the largest but by no means the only pitcher-robbing insects. No
sooner does the cobralike hood of Chrysamphora (Darlingtonia) expand and its mouth open
than the first few insect captures appear in the clear fluid which fills the lower portion of
30
the tube; and among these almost invariably appear whitish threadlike “worms” which in-
crease in numbers as the captures increase, until a writhing mass of these larvae occupy the
bottom of the pitcher, often wriggling up to surround each fresh victim as it floats and
struggles above the decaying mass of earlier captures. These larvae, to be found in almost
every open and functioning pitcher of the California pitcherplant, were a perpetual puzzle
to Mrs. Mary Austin, who sixty years ago spent so many patient hours among these plants
in Plumas County and of whom Asa Gray then wrote that she had given us most of out
detailed knowledge of these wonderful plants; for Mrs. Austin never detected the frail little
gnat, Metrzocnemus edwards, smaller than a mosquito, which lays the eggs from which these
pitcher-robbing larvae hatch. On the opposite side of our continent, a related and very similar
gnat (Metriocnemus knabi) 1s the parent of larvae which live in and rob the water-filled
pitchers of Sarracenia purpurea, wherever this plant grows.
In these same water-filled pitchers of purpurea live the ‘“wrigglets” of the pitcherplant
mosquito, Wyeomyia smithiz. Even in midwinter, when the pitchers’ contents have been frozen
to solid cores of ice, these larvae are there, ready to resume activity and to complete their
transformations with the coming of spring. This little mosquito, harmless to human beings
and representative of a tropical genus, yet extends its range well over the Canadian border, and
rarely 1s it absent from any considerable colony of this pitcherplant species, which constitutes
its only home.
In the drier pitchers of other species, the larger black-headed larvae of another fly may
often be seen hollowing out the bodies of the captured insects and eventually constructing
frail frothlike cocoons among these remains. This insect has been named Sciara macfarlanet
in honor of Dr. John M. Macfarlane, the monographer of the pitcherplants of the world.
With somewhat similar habits, the young of a few other small flies are occasionally to be
met with, taking advantage of the store of animal food provided by these plants; but most,
if not all, of these are only casually present as scavengers, and not as obligatory associates of
the pitcherplants.
PITCHER DWELLERS
We have not yet exhausted all possible variations of insect association with these plants;
for some species visit or utilize the pitcherplants, not as sources of food supply, but to adapt
the pitcher structures to other purposes of their own—usually as shelters for themselves or
for their young. The little tree toads, of which mention has already been made, may often
be seen sitting within the mouths of the larger pitchers; but since it is the habit of these
creatures to seek any small cavity which offers them seclusion for the day, their presence in
the pitchers may have no further significance, even though it may permit the occasional
capture by them of attracted insects.
Spiders of many species occur in and about the pitchers, and it may be said of one kind
that it does sometimes utilize the pitcher’s structure. A large Lycosid spider, whose habit tt
is to carry about and protect its spherical egg sac, sometimes roughly barricades the mouth
31
of a dry pitcher with coarse cobweb and vegetable litter, and within the cavity thus created,
guards its treasured eggs until the hatching of the young.
The petals of Sarracenia are often neatly scalloped by a leaf-cutter bee, which occasionally
utilizes a dry pitcher for its nest, building therein its series of thimble-shaped cells and storing
them with food for its young.
There is one insect, however, which by frequent and habitual use of the pitchers of several
species of Sarracenia, deserves to be called the Sarracenia wasp. This is a slender-waisted black
wasp which plugs the lower portion of a pitcher with grass or moss, partitions off a series
of cells, provides each in turn with a store of freshly killed grasshoppers or of tree crickets,
deposits one of its own eggs in each of the cells, then tops this nest with a densely packed
wad of grass or moss, completely closing the pitcher above. The geographical distribution
of this wasp is more extensive than that of the pitcherplants it inhabits, so elsewhere it must
utilize other cavities; but at least from North Carolina to southern Mississippi, wherever
suitable Sarracenias abound, they are utilized by this wasp as sites for its nests.
ECOLOGICAL COMPLEXITIES
These insect-eating plants, dependent upon insects for their pollination, fed upon in all
their parts by other insects, systematically robbed of their captures, dwelt in by other series
of insects, would seem to illustrate every imaginable relationship between the plant and
animal worlds; but in reality these enumerated relationships present only the framework of
further ramifications of conflicting interests, which extend to the vertebrates as well as to the
lowlier representatives of the animal world.
By what deterrent qualities are the pitcherplants protected against grazing animals which
crop every available mouthful of grass among their conspicuous growths, but which leave
the showy pitchers untouched? It was a quaint conceit of Miller (1739) that the water-
filled pitchers of Sarracenia are providentially provided drinking fountains for thirsty birds;
and Catesby interpreted them as safe retreats for insects when endangered by their foes. In
reality, birds are sometimes concerned with what goes on within the pitchers: the Exyra
caterpillar which cuts a drainage hole and an emergence hole in an otherwise closed pitcher
in preparation for pupation and the emergence of the moth, by these slight external signs
gives notice to sharp-eyed birds that a desirable food-morsel is hidden within; and sometimes,
on the pitcherplant meadows of the south, it is difficult to find a pitcher bearing these indi-
cations that has not been slit lengthwise by the beak of a searching bird which has learned
their significance.
We do not know how many kinds of predators—wasps, spiders, Acarids—habitually prey
upon pitcherplant insects; but of parasitic insects which attack them, the number is not,
small. Even the minute egg of the pitcherplant moth, glued to the pitcher's inner wall
often yields, instead of its rightful occupant, a little caterpillar, a motelike parasite; this under
the microscope proves to be an unbelievably small wasplike creature complete in all its parts,
32
wings, legs, eyes, antennae, whose parent must have searched out the minute egg of Exyra
and whose entire life cycle must have been completed within the eggshell’s bounds. Other
and larger parasites, some wasplike, some two-winged flies, are fatal to the larvae of Exyra,
and perhaps the brief exposure of these larvae when occasionally they move from pitcher to
pitcher may give opportunity for the parent parasite to deposit its egg on the otherwise
well-hidden caterpillar. The larvae of the pitcher-robbing Sarracenia flies would seem reason-
ably safe from parasitic attack; but their brown puparia often yield not flies, but whole flocks
of little wasplike parasites which emerge in a procession through holes gnawed in the rigid
walls of a puparium. The rootborer, Papaipema, also has its parasites. The larvae of the Sar-
racenia wasp in their well-packed cells are not immune; nor are parasites their sole danger; for
before the rightful occupant of a cell has had time to consume its store of food, this is often
plundered by ants or by other insect scavengers. Ants, too, though among the more frequent
victims of the leaf trap, sometimes actually build their nests in a dry pitcher (do they drain
it first?), and even construct a paperlike narrow-entranced door across 1ts mouth, excluding
other insects. Thus all sorts of complications arise, when insects having conflicting interests
attempt to occupy the same pitcher. Not rarely, an Exyra caterpillar, closing a pitcher for its
own use and thus preventing the entrance of other insects, incidentally starves the Sarcophaga
larva already ensconced below and dependent upon the entrance of fresh victims for its food.
So, from our observation of the complicated relationships which reveal the pitcherplants
as focal points of contact between the plant and animal worlds, emerges a more vivid reali-
zation that in nature each plant, each animal species, exists for itself alone; that its whole
economy of life relates to its own growth, its own safety, its own specific survival; and that
in the attainment of these ends, its environment is not confined to the obviously imma-
nent, but that its expanding circles of influence fade from our view into the distant and
the remote.
33
BIBLIOGRAPHY
This partial bibliography of the Sarraceniaceae in their relations with insects includes the
more significant literature consulted in the preparation of the preceding article, and the papers
listed include more detailed treatment of the various phases of those relationships.
Rirey, C. Vv.
1875. On the insects more particularly associated with Sarracenia variolus (spotted trumpet-leaf).
Proc. Amer. Assocs Adv. Sci, 1875, set; By pp.18 2 5-
Cansy, W. M.
1875. Darlingtonia Californica, an insectivorous plant. Proc. Amer. Assoc. Adv. Sci., 1875, ser. B,
Pp. 64-72.
MeEtticHamp, J. H.
1875. Notes on Sarracenia variolaris. Proc. Amer. Assoc. Adv. Sci., 1875, ser. B, pp. 113-133.
Epwarps, Henry
1876. Darlingtonia Californica Torrey. Proc. California Acad. Sci., vol. 6, pp. 161-166.
Macrartang, J. M.
1893. Observations on pitchered insectivorous plants. Part II. Ann. Bot., vol. 7, pp. 403-458.
1908. Sarraceniaceae. Engler’s Pflanzenr., vol. 1v. 110, pp. 1-39.
Jones, F. M.
1904. Pitcher-plant insects. Ent. News, vol. 15, pp. 14-17.
1907. Pitcher-plant insects. II. Ibid., vol. 18, pp. 413-420.
1908. Pitcher-plant insects. III. Ibid., vol. 19, pp. 150-156.
1916. Two insect associates of the California pitcher-plant, Darlingtonia Californica. Ibid., vol.
27, Pp. 385-392.
1918. Dorniphora venusta Coq. in Sarracenia flava. Ibid., vol. 29, pp. 299-302.
1920. Another pitcher-plant insect. Ibid., vol. 31, pp. 91-94.
1921. Pitcher-plants and their moths. Nat. Hist., vol. 21, pp. 296-316.
Hepsurn, J. S., and Jones, F. M.
1919. Occurrence of antiproteases in the larvae of the Sarcophaga associates of Sarracenia flava.
Contrib. Bot. Lab. Univ. Pennsylvania, vol. 4, pp. 460-463.
Hepsurn, J. S., St. Joun, E. Q., and Jonss, F. M.
1920. Absorption of nutrients . . . in pitchers of the Sarracentaceae. Journ. Franklin Inst., vol.
189, pp. 147-184.
1927. Biochemical studies of the North American Sarraceniaceae. Trans. Wagner Free Inst. Sc1.,
Vols 1, pp. 1-95.
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