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Arditti, J., Elliott, J., Kitching I.J. and Wasserthal, L.T. (2012): ‘Good Heavens what insect can suck it’ – Charles Darwin, Angraecum sesquipedale and Xanthopan morganii praedicta. Botanical Journal of the Linnean Society, 169, 403–432.


Abstract and Figures

Charles Darwin, Angraecum sesquipedale and Xanthopan morganii praedicta. In this review we provide a detailed description of Darwin’s prediction of the coevolution of a long-spurred orchid, Angraecum sesquipedale, and a long-tongued moth, his correspondence on the subject, the history of the moth and the subsequent literature. On seeing the long spur of A. sesquipedale, Darwin predicted that its pollinator would be a moth with a long proboscis. For more than a century following Darwin’s prediction this was assumed to be the case. The pollinator was taken to be Xanthopan morganii praedicta, despite the fact that it had not been observed to visit A. sesquipedale flowers. Direct observations, infra-red cinematography and photographs published between 1993 and 1997 and a video made in 2004, all of which show X. morganii praedicta visiting A. sesquipedale flowers and removing pollinia, proved that Darwin’s prediction was accurate. Recent research suggests that selecti on pressure exerted by predators on the pollinators, resulted in the evolution of extreme tongue lengths and a special hovering flight.
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‘Good Heavens what insect can suck it’ – Charles
Darwin, Angraecum sesquipedale and Xanthopan
morganii praedicta
1Department of Developmental and Cell Biology, University of California, Irvine, CA 92697, USA
2Department of Psychology, National University of Singapore, S117570, Singapore
3Department of Entomology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK
4Department of Biology, University of Erlangen, Staudtstrasse 5, 91058 Erlangen, Germany
Received 29 August 2011; revised 22 January 2012; accepted for publication 15 February 2012
In this review we provide a detailed description of Darwin’s prediction of the coevolution of a long-spurred orchid,
Angraecum sesquipedale, and a long-tongued moth, his correspondence on the subject, the history of the moth and
the subsequent literature. On seeing the long spur of A. sesquipedale, Darwin predicted that its pollinator would
be a moth with a long proboscis. For more than a century following Darwin’s prediction this was assumed to be
the case. The pollinator was taken to be Xanthopan morganii praedicta, despite the fact that it had not been
observed to visit A. sesquipedale flowers. Direct observations, infra-red cinematography and photographs published
between 1993 and 1997 and a video made in 2004, all of which show X. morganii praedicta visiting A. sesquipedale
flowers and removing pollinia, proved that Darwin’s prediction was accurate. Recent research suggests that
selection pressure exerted by predators on the pollinators, resulted in the evolution of extreme tongue lengths and
a special hovering flight. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012,
169, 403–432.
ADDITIONAL KEYWORDS: Angraecinae – co-evolution – Madagascar – Orchidaceae – pollination
– sphingid moths – Wallace.
On 25 January 1862 Charles Darwin (1809–1882)
received a box of orchids from James Bateman (1811–
1897), a well-known orchid grower, not from a collec-
tor in Madagascar as suggested in a popular
biography (Moore, 1957). The names of the orchids
were not included, and Darwin could not identify
some. He wrote to Bateman, perhaps on the same day
or on the 26th (the letter has not been found; footnote
2 in Bateman, 1862a and footnote 2 in Bateman,
1862b) inquiring about their identity. Bateman’s third
son, Robert (1842–1922), who became a wealthy prop-
erty owner as well as an artist and botanical illus-
trator, replied on 28 January 1862 because his father
was ‘obliged to leave home early’ (Bateman, 1862a)
and indicated that the package contained Zygopeta-
lum crinitum Lodd., Odontoglossum bictoniense
(Bateman) Lindl., Odontoglossum pulchellum
Bateman ex Lindl., Calanthe vestita Wall. ex Lindl.,
Laelia anceps Lindl. and Angraecum sesquipedale
Thouars. James Bateman wrote on 1 February 1862
stating that he ‘was very glad...that the orchids
were so acceptable’ and added ‘Pray forgive my gar-
dener’s carelessness in omitting the names; when I
charged him with the misdemeanor he defended
himself on the ground that he could never have
supposed you could have been ignorant of them!’
(Bateman, 1862a). [This review will contain a large
number of direct quotations, some of them extensive,
due to the: (1) nature of the events being described;
(2) individuals involved; and (3) age and uniqueness
of the original literature and an effort to retain the
flavour of the times, literature, events and locales].
*Corresponding author. E-mail:
Botanical Journal of the Linnean Society, 2012, 169, 403–432. With 11 figures
© 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 403–432 403
Regardless of whether Darwin was or was not igno-
rant of some or all of the orchids, he liked the con-
tents of the package and was especially taken by the
flowers of A. sequipedale [(Figs 1A–C, F, G, 2A–C, 3A,
B, 4Ba, Ca). Several images of A. sesquipedale are
included in this review in an effort to show: (1) the
very flowers which are part of this account; and (2)
floral details and several forms of this orchid. Several
Figure 1. Angraecum sesquipedale. Bateman, A, B, the first illustrations of Angraecum sesquipedale (du Petit Thouars,
1822); C, painting of what is probably the second flower of Angraecum sesquipedale to bloom in Britain (Anonymous,
1859); D, Angraecum superbum on a tree in Madagascar (Ellis, 1858); E, Angraecum sesquipedale on a tree branch in
Madagascar (Ellis, 1858); F, Angraecum sesquipedale (Perrier de la Bâthie, 1941); G, line drawing of what may be the first
flower of Angraecum sesquipedale to be seen in Britain (1857).
© 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 403–432
Figure 2. Angraecum sesquipedale. A, flower of Angraecum sesquipedale photographed from roughly the same distance
as that at which a pollinating moth would be positioned (one of a series of photographs taken in J. Arditti’s laboratory
in the 1970s); B, Angraecum sesquipedale flowers on a plant in China (courtesy Dr Perner Holger); C, painting of
Angraecum sesquipedale from one of the most magnificent illustrated orchid works in the late 1800s, Reichenbachia, after
the species became more commonly available in the UK (Sander, 1888); D–F, Angraecum sesquipedale seeds, scale
bar =1 mm (courtesy Troy Meyers, Meyers Conservatory,
© 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 403–432
illustrations of Xanthopan morganii and X. morganii
praedicta are also included to show that there is
variability within the species and subspecies. Some
illustrations of orchids and moths are of low quality.
The reason for this is the low quality of the originals.
On 25 January 1862 Darwin wrote his friend, Joseph
Dalton Hooker (1817–1911), Director of the Royal
Botanic Gardens, Kew, twice, that he received
Angraecum sesquipedalia (sic; Darwin, 1862b) and
A. sesquipedale flowers from Bateman (Darwin,
1862c). The letters, written before Robert Bateman’s
reply, indicate that: (1) the Angraecum (Darwin wrote
Angræcum) flowers really excited Darwin; (2) he mar-
velled both times at the length of the nectary; and (3)
Bateman’s gardener, perhaps a Mr Sherratt (Cribb &
Tibbs, 2004), was right in assuming that Darwin
would know the orchids.
Darwin’s fascination with A. sesquipedale led him
to suggest ‘a kind of an arms race’ (Micheneau,
Johnson & Fay, 2010) or a ‘feedback loop’ (Fay &
Chase, 2009) which results in Angraecum spp. and
flowers ‘with ever longer spurs and hawkmoths with
ever longer tongues’ (Fay & Chase, 2009; Micheneau
et al., 2010). By making this suggestion Darwin made
Figure 3. Pollinaria, stigma and entrance into spur of Angraecum sesquipedale. A–C, successively closer views of the
anther cap and entrance into spur (courtesy Hans-Joachim Wlodarczyk, Großräschener Orchideen, W.-Seelenbinder-Str.
21, 01983 Großräschen, Germany,; D, a pollinarium showing pollinia and viscidium;
E, pollinarium on the proboscis of Xanthopan. D and E are electronic modifications of a somewhat faded painting, now
lost, which hung for years in the coffee room of the Department of Botany at the National University of Singapore before
it moved from the old Bukit Timah campus to be merged with the Zoology Department to form an Institute (now a
Department) of Biological Sciences at Kent Ridge; F, pollinarium on a teasing needle; G, the pollinaria in H inserted into
the spur opening by simulating the proboscis movement of a moth; H, lifted anther cap to show pollinia on top of the
rostellum (F–H, from a series of photographs taken in J. Arditti’s laboratory in the 1970s).
© 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 403–432
Figure 4. Postpollination movement of Angraecum perianth segments. A, a–c, Angraecum eburneum Bory; B, a–i,
Angraecum sesquipedale; C, a–d, Angraecum Veitchii, a hybrid between the two species. Abbreviations: AC, anther cap;
DS, dorsal sepal; G, gynostemium (column); L, labellum (lip); LP, lateral petal; LS, lateral sepal; O, ovary; PD, pedicel;
Sp, spur (courtesy Dr Michael S. Strauss and part of a series of photographs taken in J. Arditti’s laboratory in the 1970s).
© 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 403–432
one of his major contributions to evolutionary biology:
coevolution (Micheneau et al., 2010). This review will
concentrate on Darwin’s prediction of a pollinator for
A. sesquipedale, the moth he predicted, the coevolu-
tion between the two and the scientists who studied
In a family known for striking flowers, those of A. ses-
quipedale (Figs 1A–C, F, G, 2A–C, 3A, B, 4Ba, Ca) are
among the most spectacular (Lecoufle, 1982; Hiller-
man & Holst, 1986; Du Puy et al., 1999; Motes, 2011;
Sawyer, 2011). The species is native to the Madagas-
car lowlands (du Petit-Thouars, 1822; Ellis, 1858;
Perier de la Bâthie, 1930, 1941, 1981; Hillerman &
Holst, 1986; Du Puy et al., 1999; Anonymous, no
date). It is primarily an epiphytic and rarely a saxa-
tilic or semi-terrestrial species (Perrier de la Bâthie,
1941, 1981; Anonymous, no date). Its generic name is
derived from the Malay word for orchid, angurek
(Schultes & Pease, 1963); currently, anggrek,ang-
gerek or anggerik. The specific epithet is a combina-
tion of the Latin word sesqui (one and a half) and
pedalis (one foot long) which means foot and a half
long or wide (Stearn, 2004). In Madagascar the plants
flower from June to September whereas when grown
in England and Europe they bloom in mid-winter
(Anonymous, 1866) or roughly between December and
January (Anonymous, no date). More generally, in the
northern hemisphere flowers are produced from
October (rarely) to May (Hamilton, 1990).
Louis-Marie Aubert-Aubert du Petit-Thouars (1756 or
1758–1831) and his brother Aristide Aubert-Aubert
du Petit-Thouars (1760–1798) wanted to hire a ship
three years after the start of the French Revolution
(1789–1799) and leave France on 22 August 1792.
Their plan was to search for the lost La Pérouse
expedition which had not been seen after leaving
Australia on 10 March 1788 for New Caledonia, the
Santa Cruz Islands, the Solomon Islands, the Loui-
siade Archipelago and the western and southern
coasts of Australia (du Petit-Thouars, 1834; Jacquet,
2002, 2007). However, Louis-Marie was delayed,
having been arrested by revolutionaries, tried and
fortunately acquitted. He left France in October 1792
and arrived in Mauritius in May 1793. After that he
spent 10 years in the French Indian Ocean islands
including three and a half years on La Réunion and
one year in Madagascar. During that time he collected
plants and sent them to Antoine Laurent de Jussieu
(1748–1836) and Jean-Baptiste Pierre Antoine de
Monet, Chevalier de la Marck (1744–1829; often
known as Lamarck, the originator of the theory of
inheritance of acquired characters as a mechanism of
On his return to France in 1802 du Petit-Thouars
brought back about 2000 specimens and 600 drawings.
He used these to publish his best known work, Histoire
Particulière des Plantes Orchidées Recuieillies sur les
Trois Isles Australes d’Afrique (du Petit-Thouars, 1822,
1979), which contains descriptions of 91 species and
includes good quality line drawing monochrome plates.
One of the species (plates 66 and 67) is A. sesqipedale
(Fig. 1A, B), discovered in 1798, for which du Petit-
Thouars coined the specific epithet in allusion to the
very long spur (Anonymous, 1857). He did not intro-
duce any Angraecum plants into cultivation.
For 35 years after the publication of du Petit-Thouars’
book, it was ‘the anxious wish of Europeans to procure
[A. sesquipedale] for cultivation’ (Anonymous, 1857),
but they could not because the plant was ‘as difficult to
import as . . . to propagate’ (Anonymous, 1866). The
reasons for its ‘great rarity’ included internal strife in
Madagascar starting in 1828, an attempt at gun boat
diplomacy by the British and French in 1845, a cessa-
tion of ‘all amicable intercourse...for eight years’
starting in 1848 (Ellis, 1858) and the long voyage
around the Cape of Good Hope which resulted in the
death of many plants (Anonymous, 1866). In fact, no
plants were taken to the United Kingdom or anywhere
else until 1857 (Anonymous, 1857; handwritten note
on a painting by John Day in Cribb & Tibbs, 2004).
Early in 1853, the Reverend William Ellis (1794–
1872) was invited ‘to proceed to Madagascar, on a visit
of friendship’ (Ellis, 1858). He left Southampton on 14
April 1853 and arrived in Madagascar on 18 July of the
same year. After that he visited Madagascar twice
more (1854 and 1856), left for the last time on 18
November 1856 and wrote a book about his travels
(Ellis, 1858) which became popular. He observed both
Angraecum superbum Thouars and A. sesquipedale on
his second visit and illustrated them (Fig. 1D, E; he
carried a camera while in Madagascar, but a collection
of his photographs, now at the Getty Museum, does not
include any of orchids). His description of A. sesquipe-
dale suggests that he also collected plants on the
second trip: it was ‘most abundant and beauti-
ful...they grew most plentifully on trees of thinnest
foliage...high up amongst the branches, often throw-
ing long straggling stems terminating in a few small,
and often apparently shrivelled, leaves. The roots also
partook of the same habit. They were seldom branched
or spreading, but long, tough, and single, sometimes
running down the branch or trunk of a tree, between
fissures on the rough bark, to the length of twelve or
fifteen feet [3.6–4.5 m]; and so tough and tenacious
© 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 403–432
that it required considerable force to detach or break
them’ (Ellis, 1858).
A description of the first plant to flower in Britain
(Anonymous, 1857) also points to the second visit as
the occasion of collection and dispatch of plants to
England: ‘The Rev. Mr. Ellis...metwith it about 2½
years ago in the forest of that island, and having
succeeded in sending home three plants in a living
state one of them flowered magnificently’ (Fig. 1G).
Ellis’s wife and his grower, Mr Gedney (Cribb &
Tibbs, 2004), are not credited with bringing the plant
to flower but should have been because Ellis was on
‘renewed absence from England when Mrs. Ellis
favoured [The Gardeners’ Chronicle] with a flower
for examination, and an extremely clever sketch
[Fig. 1G]’ (Anonymous, 1857). Subsequently Ellis pro-
vided John Lindley (1799–1865) with a description of
the species in its native habitat, which included
wording about the roots that is the same as above
except for the length which is given as ‘12 or 18 feet
[3.6–5.4 m] or more’ (Anonymous, 1857).
In 1857 all plants of A. sesquipedale in England were
owned by the Rev Ellis ‘with the exception of one
communicated by him to Mr. Veitch’ (Anonymous,
1857). The fate of this plant is not known. It is not even
mentioned by James Veitch & Sons in their discussion
of the species (Veitch & Sons, 1887–1894). The second
plant owned by Ellis flowered in February 1859
(Fig. 1C). In describing the plant, Sir William Jackson
Hooker (1785–1865) stated that the flowers are some-
times as long as the plants themselves and they do not
exceed two feet in height (Anonymous, 1859).
Angraecum sesquipedale continued to be extremely
rare in cultivation (Anonymous, 1857, 1859, 1866;
Veitch & Sons, 1887–1894) until after the opening of
the Suez Canal in 1869 (Veitch & Sons, 1887–1894;
Sander, 1888; Rolfe, 1901). Therefore, it is not surpris-
ing that plants sold for very high prices (Table 1).
The descriptions and illustrations of A. sesquipedale
in Histoire (du Petit-Thouars, 1822) and Three visits
to Madagascar (Ellis, 1858) provide interesting infor-
mation and are historically valuable, but neither pro-
vides details of the kind appropriate to a taxonomic
work. Such details became available in 1941 (Perrier
de la Bâthie, 1941, 1981).
Henri Perrier de la Bâthie (1873–1958) spent much
of his life in Madagascar (1896–1933 except for mili-
tary service in 1914–1918) before returning to France
and becoming Director of Research at the Centre
National de la Recherche Scientifique (Leandri, 1962;
Jacquet, 2002, 2007). He wrote about orchids in a
volume entitled 49eFamilie.—orchide˙es, which is part
of Flore de Madagascar edited by his friend Henri
Jean Humbert (1887–1967; sometimes listed as Jean-
Henri Humbert). He also made major contributions to
Rudolf Schlechter’s treatment of the orchids of Mada-
gascar, which was appropriately entitled Orchidaceae
Perrierianae (Schlechter, 1925). Schlechter also
named 29 orchid species in 24 genera and the genera
Perrierella Schltr. and Neobathiea Schltr. in his
honour (Jacquet, 2002). In turn, de la Bâthie named
three species in three genera in Schlechter’s honour
(Jacquet, 2002).
Table 1. Price of one Angraecum sequipedale plant in 1862–1880 (Cribb and Tibbs, 2004)a
Sale Year
Conversion to 2010 value
using price index
Annual income,
£s 1860–1880
Income conversion to 2010 £
value using average earnings
Price, £ Price, £ Labourer Skilled Labourer Skilled
John Day to Benjamin
1862 20 1,460 28 16 s 71 3 s 17,200 42,400
John Russell to [ ]
1875 24 4 s 1,780 36 8 s 91 10 s 15,940 39,900
At auction 1880 19 1,480 35 9 s 91 10 s 14,900 38,500
aOn each row the price of a single plant is given for the year stated, and that value is converted to the 2010 value (latest
available) based on the retail price index changes over that period. This occupies the first 4 columns. In the last 4 columns
are given the annual average income for a labourer and a skilled worker respectively, for the period 1860–1880, calculated
as at 1870, together with those values converted to 2010 values on the basis of changes in average earnings over the
period 1870–2010. Reported sums are rounded to the nearest shilling. Annual income was calculated from daily wages
allowing 305 working days year-1 [365-(52 Sundays and 8 holidays)]. Before the pound was made decimal £1 =20 shillings
(s) and 1s =12 pence (d). On 01 April 2012 £1 =US$1.60.
Sources: L. H. Oficer and H. Williamson. 2011. Five ways to compare the relative value of a UK pound amount, 1830 to
present at and
Money.html. Some information was kindly provided by Prof. Brian Ford.
© 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 403–432
In Flore de Madagascar (Perrier de la Bâthie, 1941,
1981), A. sesquipedale (Fig. 1F; also see Figs 1A–2C,
1G, 2A–C, 3A, B, 4Ba, Ca) is described as having
‘stems...always shorter than the leaves; leaves [not]
rigid...25–30 cm long, unequally bilobed...Inflo-
rescences 1–3 flowered, shorter than the leaves;
peduncle 10–12 cm; bracts generally...a quarter of
the length of the pedicel; flowers pure white, very
large...[segments] 7–9 cm long...Sepals oval-
acuminate, 2 cm wide...Petals of the same form, but
slightly shorter (7–8 cm) and slightly wider (2.5–
2.8 cm). Labellum 6.5–8 cm long, concave and pandu-
rate, 3.5–4 cm wide above the base and 18–24 mm in
the upper third...with 2 large calluses on the sides
of the spur orifice...spur 30–35 cm long...Column
thicker (10 mm) than tall (6 mm)...(Perrier de la
Bâthie, 1981). Spur length has also been reported to
be 30 cm (Denso, 1943). More recent measurements
are (see Table 4): length 33.3 ± 4.6 cm (N=15) with
the range being 27–43 cm (Wasserthal, 1997). As in
other hawkmoth-pollinated orchids the spurs contain
nectar composed of several sugars (Table 2). Not
described are the seeds, which are small like those of
other orchids (Fig. 3D–F).
A somewhat smaller form of A. sesquipedale from
Fort Dauphin was described as A. sesquipedale var.
angustifolium Bosser & Morat (Bosser & Morat,
1972). Another small form based on a greenhouse
plant was named A. bosseri Senghas (Senghas, 1973),
but this is now considered to be a synonym of A. ses-
quipedale var. angustifolium.
Flowers (Hillerman & Holst, 1986) are greenish
when they open, but turn white within 1–3 days and
then become creamy (the sequence is Figs 1C, 2A–C,
3A, B, 4Ba). Like the blossoms of many orchids the
flowers are long lived and can remain fresh for up to
40 days (Arditti, 1992). On ageing or after being
pollinated floral segments turn yellow (in the follow-
ing sequence: Fig. 4Bb–Bh) and the petals ‘move
slightly forward to a position approximately equipla-
nar to each other’ (Strauss & Koopowitz, 1973;
Strauss, 1976). Sepal movement is in the same direc-
tion, but more pronounced. This places them below
the labellum and parallel to it. These movements
cause the star shape of the flowers to disappear. They
continue until the flower becomes a small yellow
bundle (Fig. 4Bg, Bh). The labellum moves little if at
all. In the related species, A. eburneum Bory the three
sepals and two lateral petals move minimally
whereas the labellum curls inward (Fig. 4Aa–Ac).
This also changes the initial shape of the flower
(Strauss & Koopowitz, 1973; Strauss, 1976). These
movements are obviously species specific. The post-
pollination movements of the two species are passed
to their hybrid, Angraecum Veitchii (Fig. 4Ca; Strauss
& Koopowitz, 1973; Strauss, 1976); both its sepals
and petals, including the labellum, fold inward
(Fig. 4Cb–4Cd).
The fragrance of A. sesquipedale is produced during
the evening and night. It has been described as ‘very
spicy, masculine [! sic] and sometimes overpowering’
(Hillerman & Holst, 1986), ‘strong’ (Frownie, 2005),
‘pronounced’ (M. S. Strauss, USDA, pers. comm.) and
simply as jasmine-like and/or good or pleasant which
can easily fill a room or a greenhouse. It contains 40
identified components (Kaiser, 1992, 1993; Table 3).
The scent ‘disappeared’ shortly after the flowers
folded following pollination or auxin application to
stigmas (M. S. Strauss, 1976, pers. comm.).
In a letter to J. D. Hooker dated 25 January 1862,
Darwin wrote, ‘I have just received such a Box full
from MrBateman with the astounding Angraecum
sesquipedalia [sic] with a nectary a foot long. Good
Heavens what insect can suck it’ (Darwin, 1862a). In
their letters to Darwin (Bateman, 1862a, b), neither
James Bateman nor his son Robert mentioned the
source of their plant. However, as all plants of A. ses-
quipedale in England at that time had been imported
by Ellis (Anonymous, 1857, 1859, 1866), it is reason-
able to assume that Bateman owned a plant imported
by Ellis or a division from it. Therefore, the flowers
Darwin received must have resembled or were the
same as those which flowered in 1857 and 1859
(Fig. 1C, G). Given the rarity of the species and the
high cost of plants, James Bateman’s gift of several
flowers to Darwin was a generous gesture, which
Darwin acknowledged both on pages 197 (text) and 58
(footnote) of the first edition of Contrivances and on
pages 105 and 162 of the second edition (Darwin,
1862a, 1904). It is a credit to Darwin that he dis-
cussed the flowers and their possible pollinator in the
first edition despite receiving them only 3 months and
22 days before its publication on 15 May 1862
(Darwin, 1958).
As he did with many other orchids, Darwin examined
the column carefully and noted that ‘the rostellum is
notched [Figs 3C, 5Bb2, Bb3, Bc1, Bc2] and two sepa-
rate membranous disks can be removed, each carry-
ing by a short pedicel [now called the stipe or
caudicle] its pollen mass [Fig. 5Ba, Bb1, Da1–Da3]’
(Darwin, 1862a: 186; 1904: 154). He continued with
the description of the rostellum several pages later
(Darwin, 1862a: 198; 1904: 162), ‘The rostellum is
broad and foliaceous [Fig. 3C, G, H] and arches rect-
angularly over the stigma [this can be in inferred to
some extent from Fig. 3, but appears more like a
© 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 403–432
Table 2. Nectar properties of some angrecoid and hawkmoth-pollinated orchids*
concentration (%)
Spur length/height
of nectar column (cm) Volume (mL)
(mg J–1)
Aerangis brachycarpa 15.9/14.2 20.2 Martins & Johnson (2007)
Aerangis confusa 4.5/3.9 6.9
Aerangis thomsonii 13.5/4.1 14.9
Aerangis verdickii flowers reabsorb nectar after pollination Koopowitz & Marchant
1994, virgin 14.4 na/23.6
naturally pollinated 3.2
1995, virgin 18.3
naturally pollinated 8.7
virgin 13.8 19
48 h after pollination 4.3
Emasculated na/25.1
Pollinated na/24.3
Per plant 684.2
Angraecum comorense F, G, S Jeffrey, Arditti &
Koopowitz (1970)
Angraecum sesquipedale 29.2/3.8 Darwin (1962a)
Angraecum eburneum F, G, R, S Jeffrey et al. (1970)
Angraecum sesquipedale F, G, R, S M(?) Jeffrey et al. (1970)
Angraecum sesquipedale 16.5±4 27–43/7–25 16.9±5.98 40–300 165 ± 89.91 Wasserthal (1997)
Angraecum sororium 2.8–14.7 24.9–26.9/10.1–17 66–182 Wasserthal (1997)
Angraecum Veitchii F, G, S R(?) Jeffrey et al. (1970)
15.2 4.6–33.3/na Micheneau et al. (2010)
Mystacidium venosum 16 2.5–5.5/na 1.8 F, G, S 10:3:87 Luyt & Johnson (2001, 2002)
The flowers of this species reabsorb nectar after pollination
Rangaeris amaniensis 15.6/9.1 9.9 Martins & Johnson (2007)
*F, fructose; G, glucose; M, melezitose; na, not available; R, raffinose; S, sucrose.
© 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 403–432
triangle in Figs 3G, H, 5Bb, Bc] and over the orifice of
the nectary [Figs 3C, G, 5Bb, Bc]; it is deeply cleft
enlarged or widened at the end [Figs 3C, G, 5Bb, Bc].
Hence the rostellum pretty closely resembles...that
of Calanthe [R.Br.] after the disk was removed
[Fig. 5C]. The under surfaces of both margins of the
cleft near its end are bordered by narrow strips of
viscid membrane, easily removed so that there are
two viscid discs [Fig. 5Bb1, Da1–Da3]. To the middle
of each disk a short membranous pedicel is attached;
and each carries at its other end a pollen mass
[Fig. 3F, Bb1, Da1–Da3]. Below the rostellum, a
narrow, ledge-like viscid stigma is seated [Figs 3A–C,
G, H, 5Ba, Bb2, Bb3, Bc1, Bc2]’ (Darwin, 1862a, 1904;
the wording in both editions is identical in all these
The nectary of A. sesquipedale (Figs 1A–C, F, G,
2A–C, 3A, 4Ba–Bd, Bf, Bi, 5A, 8B, D, 10A, B, E, F)
astounded Darwin. The contents of the nectary
(Table 2) also interested him: ‘In several flowers sent
me by Mr. Bateman I found the nectaries eleven and
a half inches [29.2 cm] long, with only the lower inch
and a half [3.8 cm] filled with very sweet nectar’
[‘with nectar’ in the second edition (Darwin, 1904)].
A spur of such length (Figs 1A–C, F, G, 2A–C, 3A,
4Ba-Bd, Bf, 5Bi, A, 8B, D, 10A, B, E, F) is certain to
draw attention and require an explanation and
Darwin provided one (see below). Darwin wrote that
his explanation was ridiculed (by ‘some entomolo-
gists’) only in the second edition (i.e. he referred to
comments made after 15 May 1862, the publication
date of the first edition of Contrivances). If ridicule
was published we could not find it in the publications
we consulted.
The Athenaeum, a magazine of letters, arts and
sciences in the UK, treated the book ‘with very kind
pity and contempt’ even if the ‘reviewer knew nothing
of his subject’ (Darwin, 1958). About half the review
(Anonymous, 1862c) consisted of an overview of
orchids in general, much of it direct quotes from
Darwin and the rest disparaging remarks. There is
nothing specific in this diatribe. Angraecum sesquipe-
dale and the moth prediction are not mentioned.
Darwin was right about the reviewer being ill
informed. It seems that his sole purpose was to attack
Darwin and his ideas. From a present perspective he
failed and actually made a fool of himself, but at the
time Darwin was concerned that ‘the Athenaeum
[review] will hinder sales greatly’ (Darwin, 1862d). It
is impossible at present to determine if this review
affected sales. There were other criticisms, but they
were limited, scholarly and polite, even if driven by
ideology and religion rather than science. Most of the
reviews were laudatory, as are recent comments
(Motes, 2011; Sawyer, 2011).
When not dealing with politics and governmental
matters, George Campbell (8th Duke of Argyll, 1823–
1900) dabbled in science and economics and was a
leader and publicist in the opposition to Darwinism.
In his latter capacity he devoted almost ten pages in
a book (Campbell, 1884) to Contrivances and to Alfred
Table 3. Components of the Angraecum sesquipedale
fragrance (Kaiser, 1992, 1993)*
GCMS spikes,
percent of area
Anis aldehyde m
Anisyl acetate m
Anisyl alcohol m
Benzaldehyde 1.6
Benzyl acetate 1.1
Benzyl alcohol 14.8
Benzyl benzoate 3.0
Benzyl butyrate m
Benzyl isovalerate m
Benzyl salicylate 1.0
(E)-Cinnamic alcohol m
Dihydroactinidiolide m
Ethylbenzoate m
Geranial m
Geraniol m
Geranyl acetate m
(Z)-3-Hexenol m
(Z)-3-Hexenyl benzoate m
Hydroxyquinone dimethyl ether m
Indole m
b-Ionone m
b-Ionone epoxide m
Isoamylacetate m
Isoamyl alcohol 1.0
Isovaleraldehyde 2.5
Isovaleraldoxime (E/Zapprox. 2.1) 34.0
Isovaleronitrile 3.5
Limonene m
Linalool m
cis-Linalool oxide (pyranoid) m
trans-Linalool oxide (pyranoid) m
Methyl antranilate m
Methyl benzoate 17.9
Methylsalicylate m
p-Methoxy cinnamic alcohol m
Neral m
Phenylacetaldehyde m
Phenylacetaldoxime 2.0
Phenylethylalcohol 2.5
Phenylethylbenzoate m
*m, minor.
© 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 403–432
Russel Wallace’s (1825–1913) support for the ideas
expressed by Darwin (1867a). He wrote well, with
erudition, understanding, some knowledge of the
subject and respect for Darwin, but primarily as a
creationist. Inevitably, he concluded that ‘long before
we have searched out all that the Natural includes,
there will remain little in the so called Supernatural
which can seem hard of acceptance’ (Campbell, 1884).
On the whole his criticism was that Darwin and
Wallace did not refer to ‘that function of power of
Mind which we know as Purpose and Design’ because
‘these purposes and ideas are not our own, but the
ideas and purposes of Another – One whose manifes-
tations are superhuman and supermaterial, but are
not “supernatural” in the sense of being strange to
Nature, or in violation to it’ (Campbell, 1884). He did
not ridicule Darwin’s moth prediction. What Camp-
bell seemed to argue for is the concept known at
present as ‘intelligent design’. He does it with finesse
and scholarship, even if not convincingly. The Duke’s
Figure 5. Pollination and floral structure. A, an artist’s conception of Angraecum sesquipedale pollination by a moth with
a long proboscis (Wallace, 1867a); B, Angraecum column (courtesy Walter Upton); C, Calanthe masuca. Original
explanation of symbols rearranged in alphabetical order: A, flower viewed from above, with the anther-case removed,
showing the eight pollen-masses in the proper position within the clinandrium. All the sepals and petals have been cut
away except for the labellum. B, pollen masses attached to the viscid disc, seen from the underside. C, flower in the same
position as in A, but with the disc and pollen-masses removed, and now showing the deeply notched rostellum and the
empty clinandrium in which the pollen-masses lay. Within the left-hand stigma two pollen-masses can be seen adhering
to its viscid surface. cl., in Figure C, clinandrium, the pollen-masses being removed; d., viscid disc; l., labellum; n., mouth
of the nectary; p., pollen-masses; s.s., the two stigmas (Darwin, 1904). D, pollinia and rostellum. a, single pollinium in
different positions (1, 2). One of them is cut (3) to show that it is furrowed. b, an anther viewed from above (1) and below
(2). c, three clinandria (referred to as androclinia or anther bed in the original) one (1) with two pollinia, one (2) with no
pollinia and one (3) with a single pollinium (Sander, 1888).
© 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 403–432
writings can also be read to imply that he saw Darwin
as some kind of theological teleologist (Darwin was
said to be a teleologist even more recently; Lennox,
1993), but Darwin’s own writings made it clear that
he saw the ‘contrivances’ of orchids as the result of
natural selection. So, any teleology was selection-
based and acutely antagonistic to theological teleol-
ogy and creationism. Contrivances has also been
viewed as a ‘flank movement’ against creationism and
teleology (Beatty, 2006).
Another creationism-driven reaction to Contriv-
ances was a lecture by David Moore (1807–1879),
retired Director of the Glasnevin Botanical Gardens
and the first person to report the germination of
orchid seeds under horticultural conditions (Moore,
1849). Angraecum sesquipedale was not mentioned in
the lecture (Moore, 1875) in which he complimented
Darwin. It contained no ridicule and was centred on
glorifying ‘the boundless conceptions of the Creator’
without specifically discussing Contrivances.
A two-pronged approach was taken by the Journal
of Horticulture, Cottage Gardener and Country
Gentleman. Its review of Contrivances was good even
if it did not seem to favour ‘Mr. Darwin’s theory “on
the origin of species” ’. Straddling two worlds, the
review concluded, ‘As a contribution of the very
highest order to the practical attainment of seedling
of foreign Orchids [sic,Contrivances does not deal
with seeds and seed germination], we would recom-
mend the work, apart from all speculation about the
origin and progress of the clothing of our planet’
(Anonymous, 1862a). This review did not consider
A. sesquipedale or Darwin’s prediction of a pollinator.
It contained no ridicule.
Miles Joseph Berkeley (1803–1889), a mycologist
and, according to some, the founder of plant
pathology, wrote a glowing, but unsigned, review of
Contrivances for The London Review (Anonymous,
1862b; Darwin, 1862d; Hooker, 1862c) which did
not ridicule Darwin’s prediction of a moth that polli-
nates A. sesquipedale, and did not mix religion and
Hermann Crüger (1818–1864), a German pharma-
cist and botanist who was director of the Trinidad
Botanical Gardens, corresponded with Darwin
(Darwin, 1863b, c; Crüger, 1863a, b, c) about the
pollination of Caribbean orchids and especially Catase-
tum Rich. ex Kunth. He also wrote a paper about
orchid pollination (Crüger, 1864) which although not a
review of Contrivances and Origin expressed his admi-
ration for both. Crüger did not mention Angraecum
and did not ridicule Darwin’s prediction of a moth with
a long proboscis.
William Bernhard Tegetmeier (1816–1912), a
poultry, pheasant, bee and pigeon expert, who
assisted Darwin in these areas (Richardson, 1916)
wrote a glowing review of Contrivances which was
free of ridicule, mentioned moths but did not refer to
Angraecum (Tegetmeier, 1862).
According to The Saturday Review,Contrivances
was too technical but valuable (Anonymous, 1862d).
The rest of the one-page review in this publication
simply described a few of the contrivances Darwin
enumerated in his book. Some of the language echoes
what Darwin wrote about Angraecum and moths, but
the review did not contain specifics or ridicule.
The review in The Parthenon (Anonymous, 1862e)
was broader in scope and tried to relate some of the
contents of Contrivances to Sprengel’s book on polli-
nation (Sprengel, 1793) and work by Robert Brown
(without specifying which) and Hooker (without pro-
viding initials). This review was focused on European
orchids and contained no ridicule.
William Alexander Forbes (1855–1883), a promising
entomologist who died tragically in the Niger (the last
entry in his journal was that he had high fever;
Anonymous, 1883; Beddard, 1885), took Darwin’s pre-
diction seriously and suggested without ridicule that
the moth ‘would probably be Sphingidae of some kind,
as no other moths would combine sufficient size and
length of proboscis’ (Forbes, 1873).
Wallace (1867a) replied to Campbell’s criticism of
Darwin’s theory regarding the origin of long nectaries
of A. sesquipedale and the long proboscis of his pro-
posed pollinator. He wanted to do it ‘satisfactorily to’
Darwin (1867b) and did (Darwin, 1867b). His reply
was a lucid elaboration of Darwin’s theory (Wallace,
1867a). It included a remarkably accurate illustration
of the still unknown, yet to be discovered moth with
its proboscis inserted in a flower of A. sesquipedale
(Fig. 5A). On the whole, the reply to Campbell was
non-confrontational, and preserved mutual respect
and cordiality (even as it demolished his arguments).
So much so that Campbell’s son was a pall bearer at
Darwin’s funeral.
Thomas Belt (1832–1878; naturalist and a Darwin
supporter) criticized Wallace’s account of the evolu-
tion of the nectary (as given in his book Contributions
to the Theory of Natural Selection; Wallace, 1870: 272)
on the grounds that it failed to consider adaptations
which would prevent useless insects gaining access to
the nectar, and was thus incomplete (Belt, 1874).
However, Darwin addressed this criticism in the
second edition of Contrivances, pointing out that ‘the
moth has to be compelled to drive its proboscis as
deeply down as possible into the flower’ which would
mean that any moth trying to reach the unattainable
nectar would be liable to pollinate the orchid anyway
(Darwin, 1904: 165).
We have read correspondence between Darwin and
Daniel Oliver (1830–1916; Oliver, 1862), George
Bentham (1800–1894; Bentham, 1862; Darwin,
© 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 403–432
1863a), Charles Cardale Babington (1808–1895; Bab-
ington, 1862), Joseph Dalton Hooker (1817–1911;
Darwin, 1862e, f; Hooker, 1862a, b, c), John Murray
(1808–1892; Darwin, 1862d), Asa Gray (1810–1888;
Darwin, 1862g) and James Samuelson (Darwin,
1867a; Samuelson, 1866). In all this correspondence
Contrivances was mentioned and discussed, but never
Repeated references are made here to the lack of
ridicule in reviews and comments because on page
163 of the second edition of Contrivances Darwin
states that he was ridiculed for his belief that ‘in
Madagascar there must be moths with proboscides
capable of extension to a length of between ten and
eleven inches [25.4–27.9 cm]!’ If such ridicule was
published we could not find the publication(s) or
letter(s) which contains it. This suggests the possibil-
ity that ridicule may have been verbal, perhaps
friendly, in discussions between Darwin and entomo-
logical friends or colleagues. However, it most
probably originated among the wider entomological
community, of whom Darwin wrote to Charles Lyell,
in the context of the spread of his theory, that ‘the
entomologists alone are enough to keep [the] subject
back for ½ a century’ (Darwin, 1863c).
What may be the earliest description of a moth
which could be related to, or resemble, Xanthopan
morganii praedicta was published in 1832 under the
generic name Amphonyx by a Cuban zoologist
named Felipe Poey y Aloy (1799–1891; Poey y Aloy,
1832). Amphonyx is now considered to be a synonym
of Cocytius (Rothschild & Jordan, 1903). Another
generic name, Protoparce (Burmeister, 1856), which
was applied to Brazilian moths by the German ento-
mologist Karl Hermann Konrad Burmeister (1807–
1892) is also now a synonym of Manduca. In 1856
the controversial British Museum entomologist
Francis Walker (1809–1874) erected a new genus
Macrosila, now also a synonym of Manduca (Walker,
1856) and in it described Xanthopan morganii
(Fig. 7A–C) as Macrosila morganii. He listed two
specimens, one from Sierra Leone presented by the
Rev. D. F. Morgan (about whom no information
seems to be available) and another from the Congo
provided by Sir John Richardson (1787–1865). It has
been said that Walker was paid a shilling for every
new species and a pound for each new genus and as
a result produced sloppy and poor taxonomy. Actu-
ally Walker was paid a lump sum for every cata-
logue he wrote, but this may still not have been
enough to ensure good work (http://www.ndsu.
Walker’s successor at the British Museum, Arthur
Gardiner Butler (1844–1925), moved Macrosila mor-
ganii to Protoparce as Protoparce morganii (Butler,
1876). Finally, in 1903 Rothschild and Jordan estab-
lished the genus Xanthopan (Rothschild & Jordan,
1903), and placed the moth variously known as
Amphonyx morganii,Macrosila morganii and Proto-
parce morganii in the new genus as Xanthopan mor-
ganii. They also added a new subspecies, Xanthopan
morganii praedicta (Figs 6A–E, 7D–F). The types for
the new subspecies are a holotype male (Fig. 6D) in
the collection of Oberthür, now at the Carnegie
Museum of Natural History, Pittsburgh, Pennsylva-
nia, and a paratype female in the collection of
Mabille, which is possibly also in the Carnegie
Museum. The sources of the types were not stated
(Rothschild & Jordan, 1903).
The name and classification of X. morganii praedicta
as a subspecies has survived for more than a century.
However, questions remain regarding the relation of
Xanthopan to tribe Acherotiini or the genera Cocytius
and Neococytius, and also whether taxa with
extremely long probosces form a monophyletic group
or fall within a ‘reasonably compact clade’ (Kitching,
2002). A phylogenetic analysis based on the morphol-
ogy of both adults and immature stages (Kitching,
2002) showed that: (1) hawkmoths with extremely
long proboscises do not form a monophyletic group
and (2) the relationships of Xanthopan are ambiguous
(Kitching, 2002). However, a more recent phylogenetic
analysis based on DNA sequence data placed Xantho-
pan firmly with the Cocytius group (Kawahara et al.,
Despite several descriptions of X. morganii morga-
nii and X. morganii praedicta, information on dimen-
sions and weight is limited. The available information
indicates that X. morganii praedicta is larger than
X. morganii morganii and that females (at least of the
former) are heavier (Table 4; Wasserthal, 1997). Pho-
tographs from Madagascar (Fig. 6A–E), The Gambia
(Fig. 7D–F) and Gabon (Figs 6, 7) also suggest vari-
ability in a size and coloration within and between
regions (Figs 6, 7 are included here to show this
The ‘Good Heavens what insect can suck it...
phrase (Darwin, 1862b) has been cited so often that
it is generally taken as being the prediction of
X. morganii praedicta. However, the actual prediction
© 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 403–432
Figure 6. Xanthopan morganii praedicta from Madagascar.A, male of 5th generation bred in captivity, viewed from below.
Underside of abdomen is pinkish whereas the underside of moths of the other subspecies from Africa (Fig. 7D, E) is white.
B, same male viewed from above. Coloration, wing patterns and morphology are similar to moths from Gabon, Africa (Fig. 7).
C, female of 5th generation bred in captivity. D, larger male from the wild. E, lateral view of head with proboscis and spiny
labial palps of a male. Scale bars =10 cm (L. T. Wasserthal). F, coiled long proboscis of a Brazilian moth (Müller, 1873).
© 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 403–432
Figure 7. Xanthopan from Africa. A–C, three Xanthopan morganii moths from Gabon showing differences in body and
wing size and coloration (courtesy Patrick Basquin, La Valette, France, and Rodolphe Rougerie from the Barcode of Life
Datasystems, with assistance from James Robertson). If the species Xantho-
pan morganii is variable at least to the extent seen here it is reasonable to assume that the same may be true for the
subspecies Xanthopan morganii praedicta.D,Xanthopan morganii morganii from The Gambia viewed from below,
wingspan 13.8 cm, body length in dry state 6 cm (courtesy Roy Goff). E, Xanthopan morganii from The Gambia, wingspan
13.8 cm, body length in dry state 6 cm (courtesy Roy Goff). F, Xanthopan morganii praedicta viewed from above, perhaps
the first colour painting of this subspecies, right side viewed from above and left wing from below (Oberthür, 1920).
© 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 403–432
Table 4. Body size and proboscis length of Xanthopan morganii morganii and Xanthopan morganii praedicta
Wingspan or
forewing length
Body length
Proboscis (cm)
Proboscis length/
forewing length
Weight (g) References, comments
and/or additional
informationLength Width Male Female
19.5 Rothschild & Jordan (1903)
>22 Pinhey (1962)
12 R. Goff (pers. comm.)
10.9–13 4.2–4.6 Walker (1856)
22.5 Rothschild & Jordan (1903)
19.6 ± 2.8 0 =0.73 Nilsson et al. (1985)
18.8 Nilsson et al. (1987); Nilsson &
Rabakonandrianina (1988)
~25 Nilsson (1988)
up to 25 Nilsson (1998a)
14.7–24.4 Wasserthal (1997)
7.7 ± 0.63 6.5 ± 0.70 22 ()
21.4 ()
21.7 ± 0.42 2.8 ± 0.28 1.9 ± 0.15 3.0 ± 0.31
7.3 (), 8.2 ()22(), 21.4 () 1.7–2.9 4.36 young female*
2.64 after laying 70 eggs†
1.96 same old female‡
15 ~30 Kritsky (2001)
13.8 6.0 R. Goff (pers. comm.)
15 ()
16.4 ()
22 Denso (1943)
>20 Micheneau et al. (2010)
*Prior to 7 September.
†After laying 70 eggs, 10 September.
‡One day before death, 24 September.
© 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 403–432
is in a less well known second letter Darwin wrote to
Hooker 5 days later (Darwin, 1862c): ‘Bateman has
just sent me a lot of orchids with the Angraecum
sesquipedale [this time he uses the correct name]: do
you know its marvelous nectary 11½ inches [29.2 cm]
long, with nectar only at the extremity. What a pro-
boscis the moth that sucks it, must have! It is a very
pretty case.’ This second letter is important for two
reasons. First, the fact that Darwin wrote two letters
about A.sesquipedale within 5 days to the same
recipient indicates that he was truly fascinated and
excited by this orchid. Second, this is first time
Darwin mentioned a moth. The idea that A. sesquipe-
dale is pollinated by a moth may have occurred to
him because of observations that pollinia of Orchis L.
become attached to proboscides of moths and his
familiarity with English sphinxes (Darwin, 1904).
These observations and the second letter to Hooker
(1862c) probably led to what he wrote in Contriv-
ances: ‘in Madagascar there must be moths with
probosces capable of extension to a length of between
ten and eleven inches [25.4–27.9 cm]’ (page 188 in
the first edition, Darwin, 1862a and p. 163 in the
second edition, Darwin, 1904) and ‘in Madagascar
Angraecum sesquipedale must depend on some gigan-
tic moth’ (p. 282 in the second edition, Darwin, 1904
– publication date was 1877).
Darwin died in 1882. His ‘gigantic moth’ was
described 41, 26 and 21 years after the first and
second editions and his death, respectively (Roths-
child & Jordan, 1903) and named X. morganii prae-
dicta [they actually used the orthography ‘morgani’]
for its predicted discovery. It is not certain whether
the moth was named in honour of Darwin’s predic-
tion. In the original description of X. morganii prae-
dicta, there is no mention of Darwin, only of Wallace’s
comments in Natural Selection. Therefore, it may be
that it is this prediction that was honoured. Probably
the most generous interpretation would be that the
moth was named for its predicted discovery in
general, rather than anyone’s prediction in particular.
Indeed, there is only a passing reference to Darwin in
the introduction of the ‘Revision’ of Rothschild &
Jordan (p. xli) where they referred to the ‘Darwinian
Revolution’ and the Origin in their discussion of how
barriers between species arose.
Collections which contained the male (Fig. 6A, B, D,
E) and female (Fig. 6C) specimens were known at the
time. However, the collector(s), location(s) and time(s)
of collection(s), if known, were not published (Roths-
child & Jordan, 1903). A romantic and dramatic story
in an orchid hobbyist magazine about its discovery
(Fowlie, 1969) is a contrived fable which bears no
relation to the truth or reality. The proboscis of
X. morganii praedicta is gigantically long (up to
15 cm; Fig. 6D; Table 4), but the moth itself
(Fig. 6A–D) is not gigantic. Its wingspan (up to 16 cm;
Table 4) is only about half that of the truly gigantic
Attacus atlas (up to 26 cm) and Thysania agrippina
Cramer (up to 31 cm). Xanthopan morganii morganii
is even smaller (Fig. 7A–C).
Until 1903, an unknown moth with a long proboscis,
and after that X. morganii praedicta, was assumed to
be the pollinator of A. sesquipedale. However, for most
of this time no one actually recorded visits by the
moth to Angraecum flowers in Madagascar (Denso,
1943–1944; van der Pijl & Dodson, 1966; Denso was a
businessman, German consul in Karachi and natural-
ist who collected moths; the hawkmoth Nephele
densoi was named for him by Wilhelm Moritz
Keferstein in 1870).
In fact, such visits were not observed until 1992. The
first evidence that X. morganii praedicta pollinates
A. sesquipedale was obtained when a male moth
bearing a viscidium of the orchid was captured in that
year. Visits of X. morganii praedicta to A. sesquipedale
and A. compactum Schltr. were recorded on tape in
1992 with night vision equipment to determine the
effects of swing-hovering flight. The visits were also
photographed in 1992 (130 years after Darwin’s pre-
diction; Wasserthal, 1993, 1996, 1997) and subse-
quently videographed in 2004 by Dr Philip J. DeVries
of the University of New Orleans 143 years after
Darwin postulated the mechanism of pollination
( or
All descriptions, depictions (Figs 3A–E, 5A) and
experiments (Fig. 3A–C, F, G) until then were based on
conjecture and Darwin’s experiments (Darwin, 1904).
On receiving the plants, Darwin wrote (Darwin,
1862a): ‘A green, whip-like nectary of astonishing
length hangs down beneath the labellum. In several
flowers sent me by Mr. Bateman I found the nectaries
eleven and a half inches [29.2 cm] long, with only the
lower inch and a half [3.8 cm] filled with nectar. What
can be the use, it may be asked, of a nectary of such
disproportionate length? We shall, I think, see that
the fertilisation of the plant depends on this length,
and on nectar being contained only within the lower
and attenuated extremity. It is, however, surprising
that any insect should be able to reach the nec-
tar...inMadagascar there must be moths with pro-
boscides capable of extension to a length of between
ten or eleven inches [25.4–27.9 cm]! ...Icould not for
some time understand how the pollinia [Figs 3I, 5D] of
this orchid were removed, or how the stigma [Fig. 3C,
H] was fertilised (Fig. 3G). I passed bristles and
needles down the open entrance into the nectary and
through the cleft in the rostellum with no results. It
© 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 403–432
then occurred to me that, from the length of the
nectary, the flower must be visited by large moths,
with a proboscis thick at the base [Fig. 3E, F, both
based on conjecture]; and that to drain the last drop of
nectar, even the largest moth would have to
force its proboscis as far down as possible...the to push its proboscis
through the slight pressure the whole
foliaceous rostellum is depressed. The distance from
the outside of the flower to the extremity of the
nectary can thus be shortened by a quarter of an inch
[6.35 mm]. I therefore took a cylindrical rod one-tenth
of an inch [2.54 mm] and pushed it down through the
cleft of the rostellum. The margins readily separated,
and were pushed downwards together with the whole
rostellum. When I slowly withdrew the cylinder the
rostellum rose from its elasticity, and the margins of
the cleft were upturned so as to clasp the cylinder.
Thus the viscid strips of membrane on each underside
of the cleft rostellum [Fig. 3C, G, H] came into contact
with the cylinder, and firmly adhered to it; and the
pollen-masses were withdrawn [J.A. and his graduate
student in the early 1970s, Dr Michael S. Strauss,
tried this with a teasing needle and had the same
result; Fig 3F]. By this means I succeeded every time
in withdrawing the pollinia; and it cannot, I think, be
doubted that a large moth would thus act [as in
Fig. 3E, a conjecture drawn in the 1960s in Sin-
gapore]; that is, it would drive its proboscis up to the
very base through the cleft of the rostellum so as to
reach the extremity of the nectary; and then the
pollinia attached to the base of the proboscis would be
safely withdrawn.’
‘I did not succeed in leaving the pollen masses on
the stigma so well as I did in withdrawing them-
. . . when a moth with the pollinia adhering to the
base of its proboscis, inserts it for a second time into
the nectary, and exerts all its force so as to push down
the rostellum as far as possible, the pollen-masses
will generally rest on and adhere to the narrow,
ledge-like stigma which projects beneath the rostel-
lum [Figs 3C, G, 5B]. By acting in this manner with
the pollinia attached to a cylindrical object, the pollen
masses were twice torn off and left glued to the
stigmatic surface [Dr Strauss and I managed to
deposit pollinia which were attached to a teasing
needle, but they became attached to the rostellum
without touching the stigma; Fig. 3G].’
As already mentioned, visits by X. morganii prae-
dicta to A. sesquipedale were not observed (van der
Pijl & Dodson, 1966) until 1992 when several papers
and a number of photographs (Figs 8B, D, 10A–D;
Wasserthal, 1993, 1996, 1997) were published
showing A. sesquipedale being pollinated by X. mor-
ganii praedicta on rocky coastal slopes north of Fort
Dauphin in south-eastern Madagascar during August
1992. The behaviour of captured X. morganii prae-
dicta was observed in textile gauze tents measuring
3.6 m ¥3.6 m ¥2.5 m (height) at the same site. Addi-
tional studies using captured and reared moths were
carried out in greenhouses at the University of Erlan-
gen, Germany, from 1992 until 1996 (Wasserthal,
1997). Extensive observations in Madagascar, which
showed that few flowers set fruit, were taken as an
indication that ‘there was no chance of observing a
pollinator on A. sesquipedale [in the wild of that
area]. Therefore moths were captured and confronted
with virgin flowers under optimal conditions in a
large flight tent’ (Wasserthal, 1997: 344, 346).
Before proceeding with descriptions of visits to A. ses-
quipedale by X. morganii praedicta it is necessary to
describe a tripartite coevolution between orchids,
their pollinators and predators which prey on the
latter. In Colombia a camouflaged Epicadus hetero-
gaster spider (Fig. 9Aa, arrow, 9Ad) on Cycnoches
chlorochilon Klotsch. (Fig. 9Aa, Ab) which had cap-
tured the pollinator, Euglossa fasciata (Fig. 9Aa,
wedge, 9Ac) was described as an ‘anti-pollinator’
(Ospina, 1969). Another ‘anti-pollinator’ in Colombia
(Ospina, 1969) is a white spider which mimics part of
the labellum of Epidendrum ciliare L. (Fig. 9Ca, Cb)
so perfectly that it is nearly invisible (Fig. 9Cb, arrow,
9Cc, arrow). A more sinister ‘anti-pollinator’ is the
snake Bothrops atrox (Fig. 9Bd), which lurks near the
yellow flowers of Elleanthus xanthocomus Rchb.f.
(Fig. 9Ba, Bc) and preys on visiting hummingbirds
(Fig. 9Bb) which visit them (Ospina, 1969).
Dendrobium crumenatum Sw. produces numerous
fragrant ephemeral flowers synchronously and gre-
gariously 9 days after a rain (see Arditti, 1989 for a
review). Pollinating bees (Fig. 9E) hover among the
flowers and visit them. Spiders weave webs in front of
the flowers and catch some of the bees (observed by
the late Dr Djunaidi Gandawijaja and J.A. at the
Bogor Botanical Gardens, Indonesia, in the early
1970s). Spider webs can also be seen around flowers
of Ceratochilus biglandulosus Blume (Comber, 1990;
Fig. 9D). In Canada a crab spider has been photo-
graphed on Pogonia ophioglossoides (L.) Juss.
(Fig. 9F).
Predatory spiders approximately 2 cm long of the
family Sparassidae lurk among flowers in Madagas-
car and prey on the pollinators (Fig. 8A, C; Wasser-
thal, 1996). To avoid being caught the moths swing
from side to side in what has been described as a
pendular hover (Wasserthal, 1993, 1996) or ‘swing-
hovering’. The frequency of this hovering is 1–2 Hz at
angles which range from 25° to almost 360° (Fig. 8E;
Wasserthal, 1996).
© 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 403–432
Figure 8. Pollinators, pollination, flowers and predators. A, Panogena moth feeding in the presence of a spider which is
presumably stalking it. B, Xanthopan morganii praedicta pollinating Angraecum sesquipedale (Wasserthal, 1997). This
photograph appeared on the cover of Botanica Acta (successor to Berichte der Deutsche Botanische Gesellschaft) volume
110, number 5. C, Coelonia brevis hawkmoth in the grasp of a spider which caught it in midair Wasserthal, 1996). D,
Xanthopan morganii praedicta on approach flight to a flower of Angraecum sesquipedale (Wasserthal, 1996). A viscidium
which is visible at the base of the proboscis was the first documentation of a successful visit of Xanthopan morganii
praedicta to Angraecum sesquipedale. The bright spot on the proboscis is nectar, which indicates that the moth previously
inserted its proboscis into the nectary to depth of at least 14 cm. E, stroboscopic photograph of a convolvulus hawkmoth
(Agrius convolvuli) sucking nectar from a composite inflorescence while swing-hovering (Wasserthal, 1996). Xanthopan
morganii praedicta behaves in a similar manner while visiting flowers of Angraecum sesquipedale (Wasserthal, 1997).
© 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 403–432
Figure 9. Predation on orchid pollinators. A, a, Epicadus heterogaster spider (arrow) on Cycnoches chlorochilon flower
and a Euglossa bee (wedge) it has caught. B, Cycnoches chlorochilon flower. C, Euglossa bee. D, Epicadus spider (Ospina,
1969; Joseph Arditti’s laboratory; Wikipedia/Wikimedia). B, a pit viper, the fer-de-lance, Bothrops atrox (d) lurks around
flowering plants of Elleanthus xanthocomus (a, c) to catch the humming-birds (b) which pollinate it (Ospina, 1969;
Wikipedia/Wikimedia). C, spider (arrows in a and enlarged in c) lurk on labella of Epidendrum ciliare (a, b) to prey on
pollinators (Ospina, 1969; Joseph Arditti’s laboratory). D, Ceratochilus biglandulosus surrounded by spider webs which
are intended to catch pollinators (the late James Comber; see Comber, 1990 for details about this orchid). E, Dendrobium
crumenatum with pollen-bearing pollinator (courtesy Greg Alikas, American Orchid Society). This orchid flowers
gregariously in Indonesia, Malaysia and Singapore 9 days after a rainstorm producing numerous ephemeral pleasantly
scented white flowers which attract many bees. Spiders build webs in front of the flowers and catch pollinators. F, crab
spider lurking on rose Pogonia in Canada (courtesy John Neufeld).
© 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 403–432
Hunting spiders were already in existence when
moths arose and started to evolve in response to them
(Wasserthal, 2009). Therefore, it has been suggested
that the long proboscises and swing-hovering
(Fig. 8E) evolved as a predator avoidance mechanism
(Wasserthal, 2009). This suggestion is based on con-
frontation experiments which show that long probos-
cises and swing-hovering prevent efficient predation
(Wasserthal, 2009). Thus, it may be that long-spurred
orchids such as A. sesquipedale benefitted from the
pre-existence of moths which had proboscises that
could pick up and transfer their pollinaria (Wasser-
thal, 2009). This co-opting view modifies Darwin’s
suggestion (Wasserthal, 1997) that the long probos-
cises of tropical hawkmoths such as X. morganii prae-
dicta evolved in a coevolutionary race between long
spurs (i.e. nectar tubes) and tongues (Wasserthal,
2009; also see below).
To study visits of X. morganii praedicta to A. ses-
quipedale, a captured virgin female moth exposed to
flowers during August and September in a large flight
cage (Wasserthal, 1997) ‘was uninterested in visiting
flowers but primarily rested in an alluring position.
After copulation with [a captured] male, it began
searching for flowers. The female visited two A. ses-
quipedale flowers on August 29, while the male
visited two on August 28 and three more on August
30’ (Wasserthal, 1997: 346). A viscidium of A. ses-
quipedale which must have been attached prior to the
capture was present on the proboscis of the male
(Fig. 10D).
Tongue insertion by the male and female moths into
the spur of A. sesquipedale was rapid, lasted
1.00 ± 0.16 s and did not involve swing-hovering
(Wasserthal, 1997). ‘Both hawkmoths seized the pro-
truding labellum of the flower and pressed their
heads as closely as possible towards the rostellum
and rested 6 s ± 0.84, shivering scarcely or not at all
[Fig. 10A]. They approached the flower from below
[Fig. 8B] and withdrew the tongue flying backward
and upward [Fig. 10B; this can also be seen in videos
by Wasserthal and DeVries]. This lasted 0.90 s ± 0.45.
In all cases pollinaria were removed from the flower
and attached to the moths’ tongues 4–9 mm distant
from their base [Fig. 10B, C, F]. Some seconds later,
the pollinaria stalks bent aside at a right angle from
their initial orientation parallel to the tongue axis
[Fig. 10C]. During the following visits, the pollinaria
were deposited. When entering a new flower from
below, the tongue with the pollinia passed unhindered
through the wide opening of the spur mouth. During
withdrawal, the tongue was guided by the dorsal slit
in the rostellum and the laterally exposed pollinia
were transferred to the sticky surfaces of the stigma.
The removal and the deposition of the pollinaria took
place when the moth was in leg contact with the
labellum. The last pair of non-deposited pollinaria at
the tongue base of the female remained undamaged
from August 29 to September 21 when the moth
died...’(Wasserthal, 1997: 346).
When visiting artificial flowers and those of Clero-
dendron L. and Lantana L. (Verbenaceae) male and
female X. morganii praedicta exhibited swing-
hovering (Wasserthal, 1997). Swing-hovering is nor-
mally spontaneous and needs no induction by
external stimuli. Most male and female X. morganii
praedicta exhibited swing-hovering spontaneously (16
of 19 individuals; Wasserthal, 1993). However, swing-
hovering could be elicited by mechanical means, such
as gentle touching, in the minority of individuals
(three of 19) which did not exhibit it spontaneously
(Wasserthal, 1993). Hampering of tongue retraction
has also been observed to act as a stimulus for
swinging flight. This happens when the spur of a
flower is narrow and presumably causes strong
Swing-hovering moths stop swinging when they
seize the protruding labellum of A. sesquipedale. This
is a precondition for a successful transfer of polli-
naria. Swing-hovering generally starts after contact
of the tip of the proboscis with the nectary. Only
stressed moths were already swinging when their
proboscis touched the labellum.
Regardless of whether they swing-hover or not,
X. morganii praedicta males and females visit A. ses-
quipedale flowers for nectar. No nectar was present in
five out of 20 flowers (Wasserthal, 1997). Nectar
content in the other 15 varied from 40 to 300 mL with
levels in the spurs ranging from 7 to 25 cm (Wasser-
thal, 1997; Fig. 11A, B, E; Table 2). Flowers with the
longest spurs contained the largest volume (Fig. 11A).
The correlation between volume and spur length
(Fig. 11A) and mean nectar volume (165 ± 89.91 mL)
and average column height (16.9 ± 5.98 cm; Fig. 11B,
E) suggests that nectar column height may reach a
minimal distance from the opening regardless of spur
length. Among the flowers studied the height of the
nectar column was always such that an X. morganii
praedicta with an average proboscis length (22 cm)
could reach it (Fig. 11E; Tables 2, 4; Wasserthal,
1997). Such moths can obtain 50 mL per visit with
70% of the nectar remaining out of their reach (Was-
serthal, 1997). Thus, an X. morganii praedicta requir-
ing 400–1000 mL per night would have to visit 8–20
flowers and fly for a maximum of 50 min (Wasserthal,
1997). Visits by X. morganii praedicta to A. sesquipe-
dale flowers last 0–7 s (Fig. 11D; Wasserthal,
© 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 403–432
Figure 10. Xanthopan morganii praedicta visiting flowers of Angraecum sesquipedale (A–D) and Angraecum compactum
(E, F). A, male moth positioned on the labellum during a visit. B, visiting moth flying up as it withdraws its proboscis
which has a pollinarium (p) attached to near the base of its proboscis. The pollinia lie flat against the proboscis because
their stipes are parallel to it. C, female moth with laterally positioned pollinia on the tip of a labellum. D, a male moth
flying in an enclosure immediately after its capture. The tongue bears a viscidium (v) near its base and a remnant (n)
of what is probably nectar 7.9 cm from the base. E, maximal insertion of proboscis just before the start of withdrawal.
F, pollinaria (p) are removed during withdrawal (A–F, Wasserthal, 1997). Pollinia of Angraecum sesquipedale are
transferred. Those of Angraecum compactum are not (Wasserthal, 1997).
© 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 403–432
In the second edition of Contrivances Darwin referred
to a nectary of ‘astonishing length’ exceeding
11 inches, and a ‘gigantic moth’ with a ‘wonderfully
long proboscis’ which withdraws the pollinia while
trying to drain the last drop of nectar (Darwin, 1904).
Darwin was right about the length of the proboscis,
but not regarding the size of the moth. Xanthopan
morganii morganii (Fig. 7A–C) and X. morganii prae-
dicta (Figs 6A–9D, 7D, E) are not small but nor are
they ‘gigantic’ or ‘huge’. However, this does not really
matter because only the proboscis must be long
enough, and X. morganii praedicta is certainly large,
heavy and powerful enough (Table 4) to exert the
force necessary to insert its long proboscis deeply
enough, pick up the pollinaria on withdrawing it
(Fig. 10B–D) and deposit them on a subsequent visit
to another flower (as in the simulation in Fig. 3F, G).
Referring to the flowers sent to him by Bateman,
Darwin wrote: ‘If the Angraecum in its native forests
secretes more nectar than did the vigorous plants
sent that nectary...becomes filled, small
moths might obtain their share, but they would not
benefit the plant. The pollinia would not be with-
drawn until ‘some huge moth, with a wonderfully long
proboscis, tried to drain the last drop of nectar. If
such great moths were to become extinct...the
Angraecum would become extinct. On the other hand,
as the nectar, at least in the lower part of the nectary,
is stored safe from...other insects, the extinction of
the Angraecum would probably be a serious loss to
these moths. We can thus understand how the aston-
ishing length of the nectary had been acquired by
successive modifications. As certain moths in Mada-
gascar became larger through natural selection...,
or as the proboscis alone was lengthened to obtain
honey from...Angraecum and other deep tubular
flowers, those individual plants of the Angraecum
which had the longest nectaries...and...compelled
the moths to insert their proboscides up to the very
base, would be best fertilised. These plants would
yield most seeds, and the seedlings would generally
inherit long nectaries; and so it would be in successive
generations of the plant and of the moth. Thus, it
would appear that there has been a race in gaining
length between the nectary of the Angraecum and the
proboscis of certain moths; but the Angraecum has
triumphed...(Darwin, 1904: 165).
Campbell questioned the passage above basing his
criticism on Darwin’s statement the ‘We can thus
partially [emphasis by Campbell] understand how the
astonishing length of the nectary may have been
acquired by successive modifications’ (Campbell,
1884). Campbell’s contention was that Darwin’s
‘explanations of the mechanical methods by which a
wonderful Orchis is pollinated [here the word
Orchis” seems to mean “orchid”] are indeed, as he
himself says, with great candor “partial” and partial
only. How different from the clearness and the cer-
tainty with which Mr. Darwin is able to explain to us
the use of intention of the various organs! . . . We
know, too, that these purposes and ideas are not our
own, but...’ a creator (Campbell does not use the
word, but implies it).
Darwin did indeed refer to or imply intentions and
purposes, but he always spoke of them as the conse-
quences of natural selection and the means, which
shape design, not as theological teleological tenden-
cies (Lennox, 1993) and certainly not as ‘the Living
Will [of]...a Personal God’ Campbell wanted to
inject into science and which is the main basis for his
criticism, polite and carefully worded as it was
(Campbell, 1884). Darwin did not reply to Campbell.
However, Wallace did and indicated to Darwin that he
‘shall be glad to know whether I have done it right by
you, and hope you will not be so very sparing of
criticism as you usually are’ (Wallace, 1867b). Wal-
lace’s reply to Campbell started with a pointed, long,
but well-constructed sentence: ‘The noble author rep-
resents the feelings and expresses the ideas of that
large class who take a keen interest in the progress of
Science in general, and especially that of Natural
History, but have never themselves studied nature in
detail, or acquired that personal knowledge of the
structure of closely allied forms – the wonderful gra-
dations from species to species and from group to
group, and the infinite variety of the phenomena of
“variation” in organic beings, – which are absolutely
necessary for a full appreciation of the facts and
reasoning contained in Mr. Darwin’s great work’
(Wallace, 1867a).
Wallace then elaborated on Darwin’s suggestion
regarding the origin of long nectary and proboscises:
‘Now let us start from the time when the nectary was
only half its present length or about six inches, and
was chiefly fertilized by a species of moth which
appeared at the time of the plant’s flowering, and
whose proboscis was of the same length. Among the
millions of flowers of the Angraecum produced every
year some would always be shorter than the average,
some longer. The former, owing to the structure of the
flower, would not get fertilized, because the moths
could get all the nectar without forcing their trunks
down to the very base. The latter would be well
fertilized, and the longest would on the average be
best fertilized of all. By this process alone the average
© 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 403–432
length of the nectary would annually increase,
because the short ones being sterile and the long ones
having abundant offspring, exactly the same effect
would be produced as if a gardener destroyed the
short ones and sowed the seed of the long ones only;
and this we know by experience would produce a
regular increase of length, since it is this very process
which has increased the size and changed the form of
our cultivated fruits and flowers. But this would lead
in time to such an increased length of the nectary
© 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 403–432
that many of the moths could only just reach the
surface of the nectar, and only a few with exception-
ally long trunks be able to suck up a considerable
portion. This would cause many moths to neglect
these flowers because they could not get a satisfying
supply of nectar, and if these were the only moths in
the country...further growth of the nectary [would]
be checked...But there are...moths of various
lengths of proboscis, and as the nectary became
longer...larger species would become the
fertilizers...till the largest moths became the
sole agents...the moths would also be affected, for
those with the longest probosces would get most food,
would be the strongest and most vigorous, would visit
and fertilize the greatest number of flowers and
would leave the largest number of descendants. The
flowers...fertilized by these moths being those
which had the longest nectaries, there would in each
generation be on the average an increase in the
length of the nectaries, and also an average increase
in the length of the proboscis of the moths, and this
would be a necessary result [emphasis in the original]
from the fact that nature ever fluctuates about a
mean...’(Wallace, 1867b). A recent report that spurs
of Satyrium longicauda can vary in length from 13 to
46 mm (van der Niet, Liltved & Johnson, 2011) sub-
stantiates Wallace’s assumption that some spurs will
be shorter and others longer.
Darwin’s ideas and Wallace’s logic (Fig. 5A) are still
being considered (Nilsson et al., 1985, 1987; Nilsson,
1988, 1992; Nilsson & Rabakonandrianina, 1988;
Kritsky, 2001; Johnson & Edwards, 2000; Micheneau
et al., 2008, 2010; Hoot, 2009; Kutschera & Briggs,
2009). However, Campbell’s contention that there is
‘no shyness [in] illustrating Divine things by refer-
ence to the Natural’, if it is even remembered by more
than a few, is of interest only to those who seek and/or
believe in pre-existing ‘Purpose and Design’ (Camp-
bell, 1884) in nature, rather than relying on science
and evolution.
The pollination of A. sesquipedale by X. morganii
praedicta is the best known instance of a fit between
a proboscis or tongue length and that of an orchid
spur or nectary. Less well known instances are those
of the orchids Platanthera ciliaris (L.) Lind. and the
butterflies Papilio troilus and Papilio palamedes in
the south-eastern United States (Robertson & Wyatt,
1990) and Disa draconis Sw. (sensu Linder 1981) and
the horsefly Philoliche rostrata and the tanglewing
fly Moegistorhynchus longirostris in South Africa
(Johnson & Steiner, 1997). All three (Angraecum
Xanthopan,PlatantheraPapilio and Disa
Moegistorhynchus) are examples of directional
evolutionary trends (Whittall & Hodges, 2007) toward
long spurs (Micheneau et al., 2010). These traits
evolved as a result of the interactions between the
orchid and its pollinator (Whittall & Hodges, 2007;
Micheneau et al., 2010). Two hypotheses, described as
Figure 11. Nectar: sugar content and height of column, proboscis length and coevolution. A, correlation between spur
length and extracted nectar volume (modified from Wasserthal, 1997 by the removal of data about species other than
Angraecum sesquipedale and the addition of the five lines of text at the base of the figure). B, correlation between height
of nectar column and nectar volume measured by extraction and injection (modified from Wasserthal, 1997 by the addition
of the two lines of text which start with ‘Mean’). C, comparison between Darwin’s ‘coevolution race’ and Wasserthal’s
‘pollinator shift’ models. In the ‘coevolution race’ model (A) the race is between increasing lengths of spurs and proboscises.
The ‘pollination shift’ model (B) involves the recruitment by long-spurred angraecoid orchids of pollinators which are
generalist feeders and have proboscises of different lengths. These pollinators are substituted gradually. When spurs
enlarge beyond a certain length due to evolutionary pressure by the primary visitors flowers can be exploited (i.e. nectar
can be taken from them) by illegitimate visitors with longer proboscises (*). This has been observed in interactions
between Xanthopan morganii praedicta and Coelonia solani with Angraecum compactum. Increased selective pressure is
exerted by the existence of moth species with long proboscises. Flowers become deceptive, but can still be pollinated when
spurs become too long for the primary pollinator to reach the nectar. Pollination is impossible when the proboscis is longer
than the spurs because the pollinaria are attached further from the base of the proboscis. When this happens the
pollinaria are scratched away by the forelegs when the proboscis is rolled to a loose spiral. If the proboscis is shorter than
the spur, transfer of the pollinaria is possible as long as the proboscis can get in contact with the sexual organs of the
orchid. This occurs in other angrecoid orchids. Explanation of symbols: *, illegitimate visitor with a long proboscis which
exploits flowers; black moth, orchid pollinator; grey moth, non-pollinating visitor; white moth, a moth incapable of
pollinating an orchid (modified from Wasserthal, 1997 by moving and adding labels). D, correlation between position of
fully inserted proboscis and time of insertion, stay and withdrawal (modified from Wasserthal, 1997 by the removal of data
not pertaining to Angraecum sesquipedale). E, Nectar accessibility in Angraecum sesquipedale spurs. a, moth with an
average spur length of 22 cm can obtain about 50 mL nectar from a spur of average length of 33.3 cm and an average
nectar volume of 165 ml. b, a spur 43 cm long could offer nectar to a moth with a 22-cm-long proboscis only if it contains
more than 240 mL solution. C, small volumes of nectar can be exploited if the spur is 27 cm long (Wasserthal, 1997).
© 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 403–432
competing (Micheneau et al., 2010), have been
advanced to explain the evolution of long floral spurs.
Darwin’s coevolutionary race concept (Darwin, 1862a)
attributes the elongation of spurs and proboscises to
increases over time due to increased reproduction
efficiency for the orchid and more efficient nectar
foraging by the insect (Whittall & Hodges, 2007;
Micheneau et al., 2010).
A more recently advanced sequential (or co-opting)
coevolution hypothesis (Wasserthal, 1997) which chal-
lenges Darwin’s idea of coevolution is based on the
concept that both the long proboscises and swing-
hovering evolved as a predator avoidance mechanism
and A. sesquipedale benefited from moths with these
pre-existing traits because they could pick up and
transfer pollinaria as their proboscises were long
enough (Wasserthal, 2009). According to this hypoth-
esis what occurred was a pollination shift by the plant
to X. morganii praedicta and one-sided plant adaptive
evolution; hence it is referred to as the pollinator-shift
hypothesis (Wasserthal, 1996, 1997, 1998, 2009;
Nilsson, 1998a; Svensson, Rydell & Töve, 1998; Jermy,
Criticisms of the pollinator-shift hypothesis are that:
(1) evidence for predator avoidance is not unequivocal,
(2) there are no quantitative data reports of consistent
ambushing of large hawkmoths, (3) only smaller hawk-
moths are sometimes captured by single large spiders
or mantids and (4) due to the large size of the long-
tongued hawkmoth guild in Madagascar it is more
likely for the long tongue of X. morganii praedicta to
have originated in a ‘coevolutionary race between
hawkmoths competing for nectar’ (Nilsson, 1998a).
These criticisms generated a discussion (Nilsson,
1998b; Samways, 1998; Svensson et al., 1998; Wasser-
thal, 1998) which was resolved in favour of the
pollinator-shift hypothesis (Jermy, 1999).
Darwin first proposed the existence of a moth with a
very long tongue which pollinates A. sesquipedale in
1862 (Darwin, 1862b, c). Such a moth was not known
at the time and Darwin wrote that he was ridiculed
by some entomologists for suggesting it. Wallace
(1867a, b), the brothers Fritz and Hermann Müller
(Müller, 1873, 1883; in Brazil and Germany, respec-
tively) and Forbes (Beddard, 1885) supported Dar-
win’s suggestion. Fritz Müller even sent his brother a
coiled proboscis of a Brazilian moth (Fig. 6F) which
although long was not of sufficient length to pollinate
an orchid with a spur like the one of A. sesquipedale.
Hermann Müller published an illustration of the pro-
boscis (Müller, 1873; Fig. 6F). The moth which polli-
nates A. sesquipedale,X. morganii praedicta, was
finally described 41 years later (Rothschild & Jordan,
1903), but it was not observed to pollinate A. ses-
quipedale then or even later (Denso, 1943). However,
such was Darwin’s authority and the force and logic of
natural selection that it was assumed that X. morga-
nii praedicta or a moth like it did pollinate A. ses-
quipedale. Reasonably accurate drawings were made
on the basis of this assumption (Wallace, 1867a;
Figs 4D, E, 6A). Actual visits of X. morganii praedicta
to A. sesquipedale and removal of pollinia (Figs 8, 10)
were finally reported 134 and 135 years after Darwin
(Wasserthal, 1996, 1997). These reports were followed
by a video in 2004 by Dr Philip DeVries of the Uni-
versity of New Orleans of a visit by X. morganii
praedicta to A. sesquipedale.
Dedication by Joseph Arditti: For Richard and Jane
Otsubo, good friends and neighbours for more than 30
years. The idea of using a quote from Darwin in a
paper about his work with orchids was first suggested
by Dr Kenneth Cameron for a joint paper (Yam,
Arditti & Cameron, 2009). We thank: Dr Roy Goff for
information about Xanthopan size and photographs;
Drs Michael S. Strauss and Tim Wing Yam for
reading and commenting on the manuscript; Dr Judy
Jernsted for library access; Marje Schuetze-Coburn of
the Libraries of the University of Southern California
(J.A.’s alma mater) for photocopies of hard-to-find
literature; Mojgan ‘Megan’ Khosravi of the Interli-
brary Loan Desk at the University of California
Irvine Ayala Science Library for securing literature
from off the UCI campus; Stefan Altevogt and Michael
Hönscheid of the German Research Foundation, for
providing literature; and all those who provided
and/or allowed us to use illustrations (they are
acknowledged individually in the captions). We have
also made extensive use of the Darwin online
resource established and maintained by Dr John van
Wyhe and hosted by the National University of Sin-
gapore and of the Darwin Correspondence Project
jointly managed by the American Council of Learned
Societies and the University of Cambridge. Both have
been invaluable resources.
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ResearchGate has not been able to resolve any citations for this publication.
Field studies in South Africa showed that floral spur length in the Disa draconis complex (Orchidaceae) varies enormously between populations in the southern mountains (means = 32-38 mm), lowland sandplain (mean = 48 mm), and northern mountains (means = 57-72 mm). We tested the hypothesis that divergence in spur length has resulted from selection exerted through pollinator proboscis length. Short-spurred plants in several southern mountain populations, as well as long-spurred plants in one northern mountain population, were pollinated by a horsefly, Philoliche rostrata (Tabanidae), with a proboscis length that varied from 22 to 35 mm among sites. Long-spurred plants on the sandplain were pollinated by the tanglewing fly, Moegistorynchus longirostris (Nemestrinidae), which has a very long proboscis (mean = 57 mm). Selection apparently favors long spurs in sandplain plants, as artificial shortening of spurs resulted in a significant decline in pollen receipt and fruit set, although pollinaria removal was not significantly affected. Fruit set in the study populations was limited by pollen availability, which further suggests that selection on spur length occurs mainly through the female component of reproductive success.
This is a large and expensive book. Free copies are not available for distribution. Please do not ask. It can be purchased from Zip Publishing ( This illustrated reference work provided a detailed scientific approach to orchid biology. There are 15 chapters: history (in Asia, Africa, Europe, New Guinea and Australia), including the history of the discovery of orchid reproduction; classification and naming of orchids; evolution of the Orchidaceae, and of plant parts individually; cytology; physiology; phytochemistry; morphology; anatomy; mycorrhiza (including orchid-fungus specificity, seed germination and root characteristics); pollination (with attention to attractants and pollinators); embryology; reproduction (including reproduction through seeds, germination, and sexual and asexual propagation); heredity and breeding; ecology (with an account of the habitats in which orchids exist, as well as notes on climate, carbon fixation, seed dispersal and conservation); and commercial and ethnobotanical uses. Each chapter has a bibliography. -J.W.Cooper This a book. The author cannot send copies. It is available for purchase at -Joseph Arditti
In this investigation of orchids, first published in 1862, Darwin expands on a point made in On the Origin of Species that he felt required further explanation, namely that he believes it to be 'a universal law of nature that organic beings require an occasional cross with another individual'. Darwin explains the method by which orchids are fertilised by insects, and argues that the intricate structure of their flowers evolved to favour cross pollination because of its advantages to the species. The book is written in Darwin's usual precise and elegant style, accessible despite its intricate detail. It includes a brief explanation of botanical terms and is illustrated with 34 woodcuts.