Monday, April 4, 2016

Luna in March


I was out checking on our bluebird boxes and nearly stepped on something pale green in the mixture of dormant and new green grass.  It was a Luna Moth (Actias luna) desperately clinging onto a few grass blades 7" tall.  It was whipping around in the wind said to be 12mph with gusts to 20 although it must have felt like more.  In the picture below you can see it being lifted by a gust.

Hanging on but almost airborne in the gusting wind

 Male with large feathery antennae -  Bugunderglass.com
Female antennae - REK
Although everything else is appearing early this spring, I was still startled to see it.  This was a female as evidenced by the smaller antennae.  Males have large plumose (feathery) antennae, "My what large antennae you have.....The better to sense your pheromones, my dear."

The subject on antennae and pheromones alone is worth a book.  An insect may rely on a hundred different pheromones during their lifetime according to Thomas Eisner, the "Father of Chemical Ecology."  Those hair-like structures on the antennae are olfactory organs.  There may be up to 60,000 on a single individual in some species.  They are capable of sensing a single pheromone molecule from over a mile away.  And there might be only one molecule in a cubic yard of air.

In the case of Luna and other silk moths, time is of the essence.  Luna moths do not eat and don't even have an intestinal system.  With a life span of a week, quick mating and egg laying is crucial.  Mating occurs usually within 24 hours of emergence from the pupa which usually occurs in the morning.  The wings are initially shriveled and expand by hanging them down as body fluid is pumped into the vein-like vessels.  They then hang on while the wings dry over 2 hours to hold their shape.  In the picture below you can see that the long trailing "tails" of the wings were twisted by the heavy winds and have dried in a spiral..
Deformed tails of the wings, whipped by the wind.
I sent the photographs to Chris Barnhart who responded that evening.  "It's a girl! Get eggs if u can".  I was embarrassed that I hadn't thought of it earlier.  Guilt ridden, I went back out at 10PM  and searched the area with a flashlight and the truck headlights, but she was gone, likely having been blown of her grass stems.

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