Friday, September 17, 2010

Caterpillars Continued...

Earlier this week I highlighted two of the more colorfully patterned caterpillars of the watershed.  The use of brightly colored patterns as a defense warning mechanism is widely documented in many animal species outside of caterpillars, however some species aren't as colorfully gifted and have to resort to other defenses to ward off predators.  The viceroy is one caterpillar that has taken camouflage to a whole new level.....

Why am I photographing bird poop you might ask? Because
if you watch this pile of excrement long enough it will begin to move.
Mutant bird droppings?  No, just an ingenious venture into defensive
camouflage by the viceroy caterpillar. The viceroy Limenitis archippus is
a member of the Brush-foot family of butterflies whose larvae are
known for their uncanny resemblance of bird droppings. Why would
 a caterpillar evolve to look like poop? It is the least likely thing for a
passing bird to investigate as potential food. Brilliant!

This viceroy was spotted munching on willow leaves, a preferred
host plant, on the creek bank.  Note the spiny antenna and the
large yellow dorsal knobs as key identifying features. Interestingly
the adult viceroy butterfly is also a mimic of the monarch butterfly
which is poisonous to birds and the viceroy eggs mimic a gall
that invades willow trees.  Sometimes I guess it is good to be
something else!


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