Wednesday, March 20, 2013

The Epitome of Spring

Male luna moth by Amy Ouchley

Finding a Luna Moth Cocoon
From Amy's Nature Journal
March, 2004

In early spring there are nocturnal visitors at Heartwood.  At night in March a thumping and fluttering sound at the window announces the arrival of a luna moth.  Poems tell of moths flying into the flame of a candle and luna moths are attracted to our lights.  These pale green moths can be 4 inches across and have long tail-like extensions of the hindwing.  They seem to be the essence of a moonlit spring night.

 The moths emerge from fragile cocoons constructed of leaves and silk.  They have over-wintered in their delicate cases as pupa and when they come out they begin their search for a mate.  Since luna moths do not have mouth-parts and can not eat, they must breed quickly.  Male moths have large, feathery antennae that are sensitive to special chemicals released by the females called pheromones.  Lunas have perfected their “signature” fragrance.

After mating the female moths search for a suitable location, a host plant, for her eggs.  This is important because the next stage of the life cycle is an eating machine called a caterpillar.  Luna moth caterpillars prefer hardwood species such as birch, hickories, walnuts, sweet gum, and sumacs.  A good, diverse upland hardwood forest provides habitat for them.  When the egg hatches on the food supply, the caterpillar begins to eat voraciously and grows quickly.  If the caterpillar does not become a meal for a migrating warbler or a resident wren, it will build a cocoon out of leaves and silk and pupate or rest.

Luna moths in the south can complete this cycle 2 to 3 times a season.   The last caterpillars to pupate will become next year’s earliest adults.

For many years I searched for a luna moth cocoon.  I knew two things:  the first that a luna moth uses leaves to construct its cocoon, the second that the cocoons would be near or on the ground.  Since leafy things decompose quickly in the moist woods of Louisiana, I knew that finding a luna moth cocoon would be unlikely unless I found a newly emerged luna moth before it took flight.  Last spring this happened.  While walking a new path I chanced upon a luna moth still pumping up its wings after emerging from its winter’s sleep as a pupa.  The moth had climbed to the top of a twig.  I followed the twig down and there was the empty luna moth cocoon.  It was a male moth, because it had feathery antennae for detecting the titillating scents of the female.  Since it had no further use of its leafy cocoon, this fragile treasure made of moth silk and dogwood leaves sits near my desk to remind me of the ephemeral stages of life’s recurring cycles.


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