BAWA, K.S. 2021. THE INTERTWINED ATTRACTIONS OF PLANTS, MOTHS, AND PEOPLE. ARNOLDIA, 78(5-6): 62-67 
The Intertwined Attractions of Plants, 
Moths, and People 
Kamaljit S. Bawa 
t was a warm and humid night in Septem- 
ber of 2003. In a tropical forest by the coast 
of Madagascar, Phil Devries, an entomolo- 
gist and noted nature videographer, swatted 
mosquitoes hovering around his face. He had 
been waiting eagerly for a visitor since seven 
o’clock. As the night transitioned to early morn- 
ing, without any signs of the visitor, the tension 
and anxiety in Phil’s mind increased. For the 
visitor, Phil Devries was inconsequential; the 
desired object was Darwin’s orchid near which 
Phil (or the Butterfly Man, as he is popularly 
known) had parked himself to photograph the 
orchid’s pollinator. 
“Good Heavens what insect can suck it,” 
Charles Darwin is said to have remarked in ref- 
erence to the nectar in the long floral tube of 
Angraecum sesquipedale, now known as the 
Darwin’s orchid, native of Madagascar.! Darwin 
had received the orchid on January 25, 1862, 
from James Bateman, a businessman, collector 
of plants, and horticulturist, who grew orchids. 
Darwin then famously predicted that A. ses- 
quipedale must be pollinated by a hawkmoth 
with a proboscis that measured at least eleven 
inches in length.” 
In 1903, almost forty years after Darwin 
intuited its existence, a hawkmoth with long 
mouth parts was described by Walter Roths- 
child and Karl Jordan. It was isolated from moth 
specimens collected on an earlier expedition 
to Madagascar by Jules Paul Mabille, a French 
naturalist. Rothschild and Jordan named the 
species Xanthopan morganii. However, it was 
not until 1992, a good ninety years later, that 
Lutz Wasserthal, a German biologist, observed 
X. morganii visiting the flowers of A. sesqui- 
pedale in real life. Only then was the connec- 
tion between orchid flowers and moths finally 
confirmed.? 
Visits of moths to flowers in the wild are 
hard to observe. And so, Wasserthal had to use 
large flight tents to photograph the two partners 
engaged in the mutually beneficial relationship. 
Finally, in 2003, after spending several nights in 
the Madagascar forest, Phil Devries was able to 
photograph the evasive moths visiting the flow- 
ers of A. sesquipedale in the wild—at around 
three o’clock in the morning.* 
The correlation between the length of the 
floral tube and the length of moth’s proboscis 
led Darwin to infer the process of coevolution, 
in which natural selection favors reciprocal 
increases in the length of the floral tube and 
moth’s proboscis. Heritable variation—in this 
case, variation in floral tube and the length of 
proboscis in moths—is the raw material on 
which natural selection acts. Between Darwin’s 
original prediction and the eye-witness observa- 
tion, 130 years had passed. Nothing in science 
comes easy. Not even for Darwin. 
It was Gregor Mendel, an Austrian monk, 
who proposed the principles of inheritance 
in 1865, based on his experiments with peas. 
From Darwin’s orchids to Mendel’s peas, plants 
have played an important role in the study of 
evolution. Curiously and coincidentally, both 
Darwin and Mendel were contemporaries, and 
although Mendel’s work filled a critical gap 
in Darwin’s theory of evolution by natural 
selection, the two men did not know of each 
other’s work! 
While Darwin is noted for his work on evo- 
lution, he is much less known as an ardent 
botanist. He was greatly interested in the repro- 
duction of plants, particularly orchids. He wrote 
several books on plants: The Power of Move- 
ment in Plants, On the Various Contrivances 
by Which British and Foreign Orchids Are Fer- 
tilised by Insects, On the Good Effects of Inter- 
crossing, The Different Forms of Flowers on 
Plants of the Same Species, and Insectivorous 
Plants. Plants were critical to the formulation 
of his ideas both about inherent variation and 
how natural selection acts on this variation to 
enable evolution. 
Facing page: Darwin’s orchid (Angraecum sesquipedale) is one of thousands of night-flowering plants pollinated 
by moths. In this case, only one pollinator can accomplish the task—Xanthopan morganii. 
SENCKENBERG COLLECTION / PHOTO: SAMMLUNGSFOTOGRAFEN.DE 
