Naturespeak A naturalist's view of the world

August 14, 2009

The One that Got Away

Filed under: Uncategorized — wykes @ 10:41 pm

I was surprised to find a Luna Moth on the porch yesterday morning.  Even though this species is very common, it’s always a rare pleasure to come upon one of these emerald beauties – especially when they come to you.  This one, a handsome male decked out in white and maroon body fur,  cast a long shadow in the low angled light of early morning. It was apparent that he’d had a rough dawn, however, because he was missing both of his “tails.” Lunas normally have long trailing tails that extend an inch or two off each hind wing. The fact that he was missing his set indicates that he survived an attack by a hungry flycatcher and was granted one more day to carry on the gene pool.

Mid August is a bit late to be seeing an adult Luna flying about. Normally the species has only one brood in these parts, which means there is only one opportunity for a caterpillar to eat, grow fat, and pupate before the onset of winter. The adults die soon after mating, so you wouldn’t expect to see one past mid summer. It takes about five weeks to grow a caterpillar to full pupation size – at which point they spin a cocoon and overwinter. In the Ohio River country and parts below to the south, Lunas have time to complete two broods before jack frost nips things in the bud. Here in S.E. Michigan we are close enough to potentially host one of these second brooders I suppose.

There is a chance that my moth was a johnny-come-lately who simply arrived at the porchlight long after the party, and the girls, were gone. Whatever the case, he probably hung about looking for some beer bottles to recycle and then decided to wait out the day while suspended from the dark brick wall under the light. That, of course, was a big mistake since insect-eating birds make a habit of visiting this porchlight  as soon as the sun peeks over the trees.  A lonely fat Luna is a great breakfast treat for a  flycatcher used to surviving on lesser creatures. Having a set of  dayglow four inch wings, set against a dark wall, doesn’t do much toward hiding a lonely fat Luna from a hungry thin bird either. He might as well have put out a “Eat at Joe’s” sign. I have found several pairs of Luna moth wings – sans their fat little bodies – under this very porch light over the years.

Although I can’t say exactly what actually happened in this case, I’m confident that a bird made at least one predatory pass at the Luna and ended up grabbing the wrong end. Instead of getting a mouthful of juicy goodness, it got a beak-full of dusty moth tails. The moth, following instinct, dropped to the ground and kept out of sight as the frustrated bird flew off with a case of dry mouth. Thus the moth survived relatively intact. These tails, you see, are meant as decoy flares to thwart predators and are not just for good looks. They are for getting away not display.

Seeing that this fellow deserved some respect for his life-preserving efforts, I carefully picked him up (see here) and placed him in a protective shrub. Here is could spend the day in a place where his greeness was more concealing than revealing. I’m not sure if he’ll ever get the chance to actually pass on those courageous genes but his tale is one worth telling the grandpillers.

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