She arrived, frazzled and exhausted, one cold April night in the midst of a drenching downpour. “Thank Heaven I’ve found you! I nearly got lost in this weather!” she told him. “It’s crazy out there!”
“Won’t you stay the night?” he beseeched her, seeing she was about to drop from fatigue.
“Thank you, but no. I’ll tend to business and then be on my way. There are others I have to see tonight or it will be too late.”
A few moments later he urged her to wait out the downpour. “Sorry!” she said. “Gotta fly!” Then she was off. “Don’t worry!” he called after her. “I’ll see to your little ones.”
“I hope they don’t eat you out of your home!” she called back. Don’t worry, he wanted to assure her again, but she was already out of hearing range. Ablaze in the bright moonlight, she was, he saw, despite the effects of the deluge, still a dazzling beauty – a painterly vision in diaphanous lime-green. He would have so enjoyed a longer visit. But now it was time to keep faith by being a good host to her offspring.
The relationship between a paper birch tree and a female Luna moth is a wondrous one. The adult moth must find a paper birch – or a tree of only a handful of other species, though in northern climates like our own it is this tree that she prefers – in which to deposit a portion of her roughly 600 fertilized eggs. She places them, about 6 or 7 at a time, on its leaves; then she must quickly find another in which to put a second portion of them, and finally a third for the remaining ones. Not a good idea to put all your eggs in one basket!
And she must do this under cover of night because of the number of daytime predators, mostly birds. The night sky is fraught with danger, too, since like the birds, bats consider her a happy meal. To fend these off, the female might well spin the tails of her wing tips in wild circles. If she is lucky, this handy skill will disorient the bat while she makes a quick get-away to complete her nocturnal mission of getting those eggs to the right trees. Heaven help her if she is delayed! She has only one week to accomplish this feat. And she cannot eat a morsel during this hectic time, for she was born without a mouth! She will be dead by the end of a week.
It has been an extraordinarily cold spring. “We don’t have spring anymore!” people are complaining to one another. But high above, in the leaves of the paper birch, the eggs are secure. Who knows how, but the little caterpillars-to-be inside them, and who are hankering to come out, know enough to stay put until the weather warms up. After hatching, these brand-new caterpillars wander about the leaf for a while, perhaps a little dazed, or overwhelmed by the dramatic change in their environment. Very soon, though, they discover their appetites. “Go on, little caterpillars! Munch away! Enjoy my leaf buffet! You won’t hurt me!” said the paper birch.
But really, there’s no need to tell them. It will be non-stop munch-time for them during the next three weeks. By then they will be full-grown and about four inches long.
At the end of their first week, then again at the second, and yet again after the third, each caterpillar will spin a small amount of silk from its mouth, then place the spun silk at the end of a leaf. At the end of the third, the cocoon is ready and the caterpillar will enter it. There it stays for about two weeks. Its ‘coming out’ takes place in the morning.
Again, it must seem like a new world to them and they immediately want to fly off into it. “No, no! little Luna moths!” warned the paper birch. “You’re not ready to fly! Your wings are still too short and stumpy, and they are too soft. You have to wait until they harden.”
This will take about two hours. In the meantime, the moths climb the trunk of the paper birch and hang by their wings so that they can be filled with blood. As evening approaches, the young moths begin to vibrate with energy. They are about to enter the big, wide world beyond the paper birch. “Bye-bye! And good luck!”
They will certainly need it. The first order of business for the young female moth will be to find a mate. Fortunately, the males are recognizable by their larger and bushier antennae – all the better to smell her pheromones, her perfume. After they mate, the female must find the right trees in which to deposit her fertilized eggs. As did her mother, she has only a week to do so. But once she finds a few trees of the right species like the paper birch and deposits her eggs on their leaves, the Luna moth life cycle can begin all over again.