She was pointing at a caterpillar that was as big as the finger she was pointing with. It was bright green, striped, and had a quarter-inch-long curved red hook at one end. It stood motionless on a stalk of one of my cherry tomato plants.
I told her that I didn't know what it was and went inside to get my camera. I grabbed a little plastic storage tub at the same time. I wasn't going to let the caterpillar eat my tomatoes, but it was a beast too fascinating to squash, so I decided to make it my guest for a while. The Neighbour Kid said she might like to take it to school on Monday, if I could figure out what it was.
It was a tobacco hornworm - Manduca sexta, more formally, and Greener, somewhat less so.
Greener and his cousins, the tomato hornworms, eat things like tobacco and tomato plants. They've evolved ways of neutralizing the toxins in tobacco plants - like nicotine - while still being able to enjoy that cool menthol taste.
They're voracious eaters - on Sunday afternoon I watched Greener chew up a section of leaf the size of a quarter in about two minutes - that devour your plants and grow quickly before turning into Carolina Sphinx moths. I was looking forward to seeing it.
A few hours later, I knew that wasn't going to happen. At about 7:30 I noticed a single white nodule, no larger than a grain of rice, on Greener's back. It was a braconid wasp larva.
Braconidae are a natural control for hornworms: adult wasps lay their eggs in the hornworm between molts, and the wasp larvae grow inside the hornworm for a couple of weeks; all the while the hornworm goes about his usual business - which is to say, eating my tomatoes. Then, at the end of the two weeks, the larvae emerge through the hornworm's skin.
In the time it took me to look up that information online - about twenty minutes - Greener went from having one larva on his back to having eighteen.
Within half an hour, he had more than fifty larvae on him, each one slowly rotating at its unattached end as it spun a coccoon.
By Monday morning, Greener's rear end was covered in coccoons. By Monday evening, The Neighbour Kid was not so interested in taking Greener to school.
Once the larvae emerged and spun their coccoons, not much happened that anyone could see. The coccoons got darker as the pupae developed. Greener eventually stopped eating and a week after the first larva popped through the skin, Greener was dead and the little plastic tub was filled with several dozen braconid wasps. They're tiny - only about an eighth of an inch long - and look like blackflies to the naked eye. Under magnification, though, they look every bit like a wasp.
The wasps themselves live for about two weeks. Each female will lay eggs in as many as 200 hornworms during that time. Greener's friends are in deep doo-doo.
Posts
No comments:
Post a Comment