[NatureNS] Nature helps moths [and butterflies] say

Date: Sat, 02 Jun 2007 16:12:37 -0300
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Chronicle Herald, Science page of Living section, Sat., June 2, 2007

[Also on the Science page today was an article titled, "Scientists disagree
on whether warming means more hurricanes", plus the Science Sleuth on "CLA
can help reduce body fat, but risky" and "Chemicals make coffee bitter".]

PHOTO: Hamadryas Amphinome -- [family] Nymphalidae -- use dark colouring to
hide on tree bark. They also make loud clicks while in flight. ( NYT)

Nature helps moths say Œdonšt even try to catch meš

By The New York Times

The gaudy swirls of colour on a butterflyšs wing, the rococo curlicues on
its riotously dressed caterpillars, may seem to be delightful examples of
naturešs artistry. But that is to miss naturešs point.

Every feature of a butterfly or moth, throughout its life from egg to adult,
has been shaped over millions of years of evolution for specific purposes.
Salient among these is escape from predators like birds, monkeys, and the
dreaded parasitic flies and wasps that lay their eggs inside the living
caterpillar.

People arrived far too recently on the evolutionary scene for moths and
butterflies to have anything to say to them. But after nearly 30 years of
studying these insects in the Guanacaste conservation area of Costa Rica,
Daniel Janzen has become an adept translator of their body language.

In two recent books, 100 Caterpillars and 100 Butterflies and Moths, he and
Winifred Hallwachs, his colleague at the University of Pennsylvania, explain
the meaning of the exotic colours and camouflage patterns. The moth
Calledema plusia never flies by day yet has learned how to imitate sunlight.
A silvery gash on both sides of its brown wings, always folded over the body
during daytime, mimics a shaft of light streaming through a dead leaf.

Many butterflies have gashes of iridescent colour splashed across their
wings. Why risk such a display? The flashes of colour accentuate the speed
of flight. Their message to birds, Janzen says: "Donšt even try to catch
me."

Other bold colour patterns, however elegant they may seem to people, are
just toxic warning labels, real but often feigned, to would-be consumers.

Many species try to pretend they are the least nutritious objects in the
forest. This generally means imitating a piece of bird excrement if one is a
caterpillar, and a dead leaf when one reaches adulthood. Another variation
is for a caterpillar to sport a disconcerting pattern like a giant eye that
can be winked at an aggressor.

A moth on which evolution has lavished a remarkable degree of protective
care is Oxytenis modestia. The first four stages of its caterpillar mimic a
bird dropping, complete with mock seeds. The fifth caterpillar stage
performs a brilliant impersonation of a green snake, complete with a bulging
head and two menacing faux eyes.

As an adult, the Oxytenis moth resembles a leaf, but even here evolutionšs
inventiveness is not an end. The moth breeds twice yearly, and each form is
different. The moths that hatch in the dry season are beige, to resemble
dry, dead leaves, and those of the rainy season are dark and mouldy looking.

Several butterflies practise a clever combination of camouflage and
conspicuousness. Pieria helvetia has demure forewings and splashes of deep
red on its hindwings. At rest, with its wings closed, it can hardly be seen.
If disturbed by a predator, it darts into rapid flight, its red patches
making it very visible. Then comes the disappearing act. It settles, quickly
folds its wings and is invisible again.

Why do birds and monkeys go to such lengths to consume these insects,
stimulating such a rich array of evolutionary strategies to evade capture?
The answer is simple. Moths taste "like raw shrimp, if one should care to
try," Janzen assures the reader.



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