Luna moth

A stunning luna moth, Actias luna, slowly dries and unfurls. I had a short hiatus yesterday, in between leading groups on explorations in northern Michigan's Presque Isle County. So Nina Harfmann and I headed over to the shores of Lake Huron and some interesting alvar habitats full of unusual plants. Nina glanced down, and spotted the luna hanging from a twig. It had just emerged from its cocoon and was not yet fully expanded.

What a face! This is a male, as can be told by the large feathery antennae. We gently picked up the twig, which was nearly in the path, and positioned it for better photos. After a female American Redstart seemed to show undue interest in us and the moth, we ended up carting the luna safely out of sight and into a well protected nook so it could continue its transformation in peace.

One doesn't often stumble into lunas, and I felt especially fortunate to see one yesterday. My Columbus Dispatch column, Nature, ran the same day, and you can read that and see what the subject was, below:


The Columbus Dispatch
Sunday, May 20, 2012

NATURE
Jim McCormac

Luna: big, beautiful moth

The world of moths is vast and underappreciated. Many people notice these creatures of the night only as fluttering brown wraiths clouding around the porch light. Yet these seemingly bland insects are among the most important animals in nature. For every adult moth that we see, scores of caterpillars — which ultimately become moths — perish. Moth caterpillars are a vital food source for legions of songbirds, wasps, beetles and other predators. Only a tiny percentage reaches the flighted stage. Even after the moths spread their wings, bats and birds such as flycatchers eat them.

Ohio is moth-rich; approximately 2,500 species occur in the state. Most moths won’t win any beauty contests, and few people other than hard-core entomologists pay them any mind.
But there are lepidopteran luminaries so beautiful that they would stop anyone in their tracks.

Foremost among the ranks of gorgeous moths are the giant silkworm moths of the family Saturniidae. There are only eighteen species of these flashy jumbos in Ohio, and all of them are eye-catchers.

The biggest silkworm moths are bat-sized, such as the cecropia with its 6-inch wingspan. Not far behind in size is the luna moth, a creature so stunning that its image is often reproduced, making the luna the most recognizable of North American moths.

A luna begins life as one of up to 300 eggs deposited by a female moth on an appropriate host plant. Suitable fodder includes tree species such as beech, cherry, hickory and walnut. After 10 days or so, minuscule caterpillars pop from the eggs and begin to feed on leaves. Every week, the caterpillar casts off its skin and emerges a bit larger. These growth stages are termed instars, and a luna caterpillar goes through five instars before reaching maturity. At that point, it is a glorious 3-inch lime-green sausage with bearlike grasping legs, ornately marked with orange dots and bristling with stiff hairs.

The mature caterpillar will soon fashion a cocoon, and late-summer luna hatches spend winter in this state. Earlier-season luna broods spend two weeks undergoing a remarkable transformation from caterpillar to moth within the cocoon. On the fateful morning, the moth wriggles free of its cocoon and begins a brief process of expansion by pumping fluid through its wings and body.

Voila! The result is a moth of staggering beauty. An apple-green luna is a sight not soon forgotten. Its massive forewings are trimmed in purplish-brown, and the hindwings feature stunning tail streamers that are twisted like confetti. How could such a showy animal hide from predators? Spot a luna dangling from a branch and the answer is apparent. The moth is a consummate plant mimic, its purple forewing edge resembling a twig with dangling buds, and the green wings are leaves.

It seems a crime that such an intricate creature lives but a week. Adult lunas exist only to mate and deposit eggs. They lack functional mouthparts and don’t eat. Males possess large fernlike antennae filled with sensitive receptors more acute than a bloodhound’s nose. They can detect the female’s airborne pheromones from a mile or more. After rendezvousing at night, their task is complete, and another cycle of gorgeous but all too ephemeral moths are set in motion.

Naturalist Jim McCormac writes a column for The Dispatch on the first and third Sundays of the month. He also writes about nature at www.jimmccormac.blogspot.com.


To learn more
A wonderful new moth book has just emerged: the Peterson Field Guide to Moths of Northeastern North America (Houghton Mifflin Harcourt, $29) by David Beadle and Seabrooke Leckie. It covers almost all of the species that one could expect to find in Ohio. Plenty of excellent photos are packed into its 600-plus pages.