64 Arnoldia 78/5-6 « October 2021 
Moths and Sex Pheromones 
It is March 1974, and I am waiting, at evening 
time, under a large Luehea speciosa. The tree 
stands in a dry tropical forest in Guanacaste 
Province, Costa Rica. The previous day, I had 
seen its large white flowers start to bloom 
around eight o’clock in the evening. And so, 
the next day, under the tree and in the light of 
the moon, I staked a vantage point and started 
my watch. At exactly a quarter to eight, and 
almost like magic, the large white petals start 
to unfurl. In a quarter of an hour, almost a hun- 
dred flowers in my field of view have opened in 
near-perfect synchronicity. In my five decades 
of fieldwork in Costa Rica, that night was one 
of the most memorable and remains perma- 
nently etched in my memory. 
Plants depend on a wide variety of animals 
to get cross-pollinated. The diversity of these 
pollination systems is on full display in tropi- 
cal evergreen forests, the world’s most species- 
rich ecological communities. On any given 
day, at any time during a short walk through 
the forest, one can encounter flowers of many 
sizes, shapes, and colors that are pollinated by 
insects—largely bees, butterflies, and flies— 
and, at times, birds. For a different set of plant 
species that start to open their flowers around 
dusk and at night, insects (beetles and moths) 
and mammals (primarily bats) take over the role 
of major pollinators. 
All across the globe, but mostly in the trop- 
ics, tens of thousands of plant species are pol- 
linated by an equally large number of moth 
species at night. Moth-pollinated flowers are 
almost always white and tubular, with nectar at 
the base of the tube. They blossom in the eve- 
ning, soon after dusk, and the blooms last for 
one or two nights. During this time, the moths 
visit them frequently, making multiple forays 
throughout the hours of the night. 
Insect pollinators visit flowers for food, but, 
to them, flowers are more than a food source. 
They are also sites of mating and, often, a source 
of compounds that play an important role in 
facilitating these sexual encounters. Flowers 
produce a variety of volatile compounds to 
attract insects, such as moths. Smell plays an 
important role in attracting insects from afar, 
especially at night, when visual cues can only 
function once the pollinators approach the 
flower closely. 
Female moths use volatile compounds pro- 
duced by flowers to synthesize sex pheromones, 
which they release to attract males. In some 
cases, the volatiles associated with the floral 
smell simply induce female moths to produce 
large amounts of sex pheromones, but in oth- 
ers, the female moths can absorb or ingest the 
volatiles and convert the compounds directly 
into pheromones. The males are not left behind. 
In some species of moths, males sequester pyr- 
rolizidine alkaloids from flowers to use them 
as precursors for the synthesis of pheromones. 
Sometimes, the males even transfer the alka- 
loids to the female during mating, for the 
defense of eggs against predators. Thus, flow- 
ers play a critical role not only in the provision 
of food and nutrition but also in the mating and 
reproduction of pollinators. 
Evening Fragrances and Romantic Nights 
Thirty years later, I am in Bangalore, the 
techno-hub of South India. It is again late eve- 
ning, and I am passing through a small market 
buzzing with people. Walking in front of veg- 
etable and food stores, I am overpowered with 
fragrances emanating from buds and flowers 
of jasmine (Jasminum) strung together for hair 
adornments. And indeed, I see many women 
walking around with their long hair arranged in 
many different styles and adorned with strings 
of fragrant jasmine. 
Throughout remembered history, and for mil- 
lennia, flowers have been a part of daily life 
in India, as adornments for gods and humans. 
The Hindu epic Ramayana about the life of 
Ram, one of the most celebrated gods of Hin- 
dus, includes references to Sita, Ram’s wife, 
decorating her hair with floral arrangements. 
And in a well-known epic poem written in the 
fourth century CE, the playwright Kalidasa 
included a verse in which sensuality and pol- 
lination merge: 
Sensuous women 
in summer love 
weave 
flower earrings 
from fragile petals 
of mimosa 
