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At night in a tropical rain forest, strange
things can happen. Your head lantern creates eerie, moving shadows
that distort the landscape. Occasionally an insect will fly into
the lantern, and be projected in enormous silhouette on the nearby
trees.
The most startling and unexpected visitors to
my head lantern have been giant silk moths. These bat-sized
insects can appear from nowhere, their wings flapping audibly;
more than once, I have jumped in alarm at the sound, and at the
sensation of one brushing past my ears in the dark.
These nocturnal apparitions are the passion of
Entomology Section Research Associate Kirby Wolfe, a scientist who
has captured some of the mystery and beauty of the giant silk
moths in his photographs. Concentrating his efforts in the New
World tropics, where the world's greatest diversity of saturniids
is found, he has sought these insects in Central America, Mexico,
Colombia, Ecuador and Chile. While not without risks (he was once
captured by guerrillas in Guatemala), these journeys have been
rich in the rewards of discovery. Wolfe has chronicled the life
history and immature stages of many known silk moths, and has
described a number of new species.
Giant silk moths belong to the family
Saturniidae, a group that includes about 1300 species and some of
the world's largest moths: the hercules moth of Australia has a
wingspan of up to twelve inches (30 centimeters), and in North
America the polyphemus, luna, cecropia and ceanothus silk moths
are all among the biggest night-flying insects in their ranges.
There are small species, but in general saturniids live up to the
title of "giant."
Saturniids are not only big, they are also
beautiful. With colors ranging from intense browns to pale greens
and bright oranges, their wings are accented by bright eyespots
that presumably startle predators seeking a meal. Some species
have incredibly elongate hind wings that trail behind them in
flight, and have earned them common names like "Tailed
Comet." For all their beauty, the lifespan of the adult moth
is short; because they lack mouthparts they do not feed, and will
live only a few days, long enough to mate and produce the eggs
carrying the next generation.
The caterpillars that emerge from the eggs do
feed. In this immature stage, many are as striking as the adults,
with bright color patternss and feathery and spiny projections
that, although dramatic, nevertheless serve as camouflage.
Caterpillars of some species have poisonous bristles, and have
been responsible for the deaths of people unfortunate enough to
have bushed against a large number of them at once.
To obtain photographs, Wolfe captures a female
that is attracted to lights and places it inside a plain paper
bag, where over the next day or so it will usually lay eggs. Once
these hatch, Wolfe rears the resulting caterpillars on their
preferred food plant, photographing them at various stages of
growth. When feeding is finished, the caterpillars metamorphose
into pupae, the life stage in which the body tissues are
reorganized to form the adult moth.
Near the end of the metamorphosis, the wings
become shiny and the pupa elongates. Then the adult emerges,
pumping its wing veins full of blood and slowly spreading its
wings. It is at this point that Wolfe photographs the moth: with
perfect, unruffled wings and unscarred body, it is at the prime of
its short life.
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