Of Giant Silk Moths

My internal struggle was strong. Should the cecropia moth remain caged for the night, where it would be safe? Or, should I set him free to survive in the urban wilds – dodging cars and cats and raccoons?

Ultimately, some might say that I’m not a good butterfly rancher. I just had to let him go.

Last summer, I happily fed Mexican plum leaves to the green toy-like caterpillars until they were as fat and long as a bratwurst. I even had a friend "caterpillar-sit" when I was out of town last May. From three caterpillars, only two survived to spin their tough brown cocoons shrouded with crunchy dead leaves. And these two wintered over in a vintage wooden pet carrier that John found in someone’s garbage pile - quietly resting in a corner of the garage.

There, their internal clocks were synced with the seasonal changes in light and temperature that would help their cells know when it was time to awake.

As caterpillars in the house, they were safe from roving tachinid flies, looking for a fat juicy larvae to support their brood of parasitic larvae. In the garage, they were safe from rodents and birds looking for a midwinter snack.

And then yesterday, 10 months after the caterpillars had disappeared into their silken cocoons, one of them emerged. With damp, weak wings, it squeezed through a hole in the top of its lair. By the time I came home from work, its glorious rusty brown and red wings – spanning at least five inches across – were fanning and pulsing in the warm evening air. Eye spots flashing. He was warming up to fly.

This cecropia’s long feathered antennae clued me in that it was a male. In this species of silk moth (the largest in North America), the females produce a strong pheromone that can attract males from miles away. The males’ antennae are filled with sensors that pick up the scent. And the more surface area on the antennae, the more chance they’ll catch a whiff of the female.

Both male and female cecropia (Hyalophora cecropia) have these feathered antennae, but the males’ are much larger. Another way to distinguish the females from males is that the ladies are plumper. Their abdomens are filled with eggs waiting to be fertilized.

These gorgeous creatures only live as free-flying adults for a few days. They have no mouths, because they don’t eat. Their sole purpose is to mate and find a suitable tree to lay their eggs. They love plums (Prunus), as well as apples (Malus), dogwoods (Cornus) and willow (Salix).

In the end, I just couldn’t keep my moth from doing what he was supposed to do: go forth and multiply. It’s in his destiny to dodge his way though our crazy world and follow the scent of a waiting female. So, I daintily lifted him from the cage - his fuzzy soft legs wrapping around my finger - and let him fly away into the night.

I hope he didn’t get hit by a truck screaming down to Laredo on I-35. Or get seduced by a porch light and find himself stuck in a vortex of light.

In my mind’s eye, he found a mate (or more), and she then deposited her eggs on the Mexican plums now flush with new tender leaves perfect for the small mouths of newly hatched caterpillars. I’ll be keeping an eye out for those, even though chances are low to find them in the wild.

Sadly, cecropias and many of our other large silk moths are rarer now. They’re populations have decreased as a result of attacks from a European fly that was introduced here to combat the highly invasive gypsy moth.

Here’s hoping that my nurturing of this one will lead to more out there in the wild, living their secret, beautiful lives amongst the shadows and the trees. In the meantime, there’s still one cocoon sitting in my cage, waiting for its time to fly.

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Many thanks to folks at the Austin Butterfly Forum who lent me the caterpillars. If you are looking to see more cecropia, the Wildflower Center always raises herds of them in their butterfly house each year.