Thursday, June 28, 2007

Insect moral dilemma of 2007

Remember my Forest Tent caterpillar? I found it in Central Park on May 11th.

It lived in my office in a nice airy jar I bought for it at the Container Store, and every day I went to Union Square Park across the street to collect fresh leaves for it: usually there were little twiglets of elm leaves lying on the ground that squirrels had obligingly broken off.

On June 14 I was a bit worried; my little pet [and excellent procrastinatory device] had stopped eating. How did I know? There wasn't the usual collection of frass [insect droppings] at the bottom of the jar when I arrived in the morning. I went out to get the handsome creature new leaves--maybe it was bored with elm!

Something seemed wrong with the caterpillar. It had stopped its usual munching and was now wandering around the jar restlessly. I was curious to see that from the tip of its adomen it was spinning a thin, silklike thread on the side of the jar. As it went back and forth it was creating a sort of spider-webby mass. Aha! It was a forest TENT caterpillar. This looked like it might be the tent.

Then the next day, June 15th, I found my caterpillar had completely vanished. Below you can see its replacement: a pupa in a fine silken tent.

As you may remember I had a moral dilemma to resolve about this creature. According to Charles V Covell, author of the one and only field guide to moths, the forest tent caterpillar [Malacosoma disstria] is "a serious defoliating pest". If a moth did emerge from the coccoon and if I chose to release it, it would quickly find a mate and the female of that pair would lay a large mass of eggs. She'd wrap it around a twig somewhere and there it would overwinter. Next spring hundreds of adorable little forest tent caterpillas would hatch and DESTROY TREES.

Well, dear readers, this morning I came to my office and discovered that the next amazing phase of metamorphosis had occurred: in the jar was an empty coccoon and... a pretty light brown moth.

When I first wrote about the forest tent caterpillar here , correspondent Jan Lipert wrote: You're in for it now! You've created the Insect Moral Dilemma of 2007. Have you ever heard the saying "No good deed goes unpunished" ?

Earlier, another reader, Cathy Doyle, had written in to suggest that I drop off the caterpillar at a bird feeding area where mom and dad could bring it to their babies. "At least it would be a natural death and he would have done his share in helping the environment and not destroying it," she wrote.

I should have done that, but I didn't. I was too eager to see metamorphosis in action.

Now what?