Monday, October 03, 2005

The caterpillar's girdle

Very slim pickings at the Moth Tree last night, two small triangular-shaped moths called Common Idias and one Large Yellow Underwing, a very common exotic insect that is actually not an Underwing at all. That was it.

Then Nick Wagerik mentioned that a Black Swallowtail caterpillar had been seen at the Shakespeare Garden earlier in the day. Maybe it had begun its transformation into a chrysalid. It would spend the winter in that form and release its butterfly sometime next spring.

At about 8:30pm we abandoned the moths and headed for the garden

We found the striking larva easily. It had picked a very familiar [to us]spot to pupate --- a slat of a latticework fence directly in front of the bench where the Central Park non-maternal Mothers always set up their black light on hot summer nights.

Unlike the Monarch caterpillar, that spins a chrysalid hanging from a plant stalk [see previous website entries -- 9/20 and earlier] the Black Swallowtail caterpillar attaches a chrysalid to a stalk -- or in this case, a wooden slat, by means of a "girdle" encircling its body. You can see the girdle thread going from the caterpillar to the slat at the upper right part of the caterpillar, near its head. It looks like a thin thread. The part of the girdle that goes around and then attaches on the other side cannot be seen. It is under one of the folds of the larva's back.

The stunning pale-green, yellow, and black creature has not pupated yet -- that is, it has not transformed itself into a chrysalid. But it will do so soon -- it has definitely attached itself to the latticework fence. The transformation is extremely fast -- less than a minute, Nick says. I hope I'll manage to see it. I'll be at the garden with my little camera early this afternoon to check out its progress. Very exciting.