July 26th, 2007
update on the yellow bear caterpillar
As some of you will remember, back on July 9th, I wrote:
Yesterday, I collected the caterpillar below — what is, in all probability, a Virginian Tiger moth (Spilosoma virginica), often referred to as a Yellow Bear caterpillar. It was found on the tall Sweet Clover plant (Melilotus alba), which is often seen growing along roadsides. I collected a few sprigs to put in the caterpillar’s new home. I’ve recorded the date that the caterpillar was collected, and I’ll try to record the date that it cocoons.
Well, I didn’t have to wait long. The caterpillar that I collected on July 8th (see above – click on all images for a larger view), had cocooned by July 10th. I’ve often found that caterpillars will cocoon soon after they are collected and placed in a container with their food plants. I don’t know if this is really a response to being moved – almost a form of rebellion to being confined – or if it is just coincidental and more related to their life stage when I happen to find them. I believe it’s actually the latter as large final instar caterpillars are generally the most conspicuous, both in size and in the damage that they do to plants while feeding. In all probability, the caterpillars would have pupated within a day or two even if I hadn’t seen and collected them.
The cocoon of the Virginian Tiger Moth (see above) consists of a dark, glossy-shelled pupa, surrounded by a sort of capsule made from the remnants of the caterpillar’s setae (the “hair” on the caterpillar’s body). This caterpillar attached its cocoon to the leaves of the still green Sweet Clover, but as I had clipped these from the plant, they wilted and dried. This had no effect on the caterpillar within its cocoon.
Yesterday, I examined the cocoon and thought to myself that the moth should be emerging soon, or else it’s dead – perhaps parasitized by another insect. However, this morning, Don noticed the moth on the living room window. I checked the cocoon, and sure enough, there was an “escape hole” in one end (you can see that in the cocoon photo). So, it took about 16 days for the caterpillar to become transformed into the above moth.
One of the very neat things about moths is that the forewings often conceal beautifully marked hindwings or bodies. That’s certainly the case with this moth as the body is marked with bright yellow and black.
As for the “moth project” mentioned in my previous post, it’s not progressing quite as hoped. I have seen a few caterpillars around, but always at times when I was carrying two cameras and no collection containers. At the moment, the main caterpillar project is raising part of the colony of larvae found on the Buckthorn bushes (mentioned in another recent post). I’ll post an update on them later this week.
By the way, just a reminder that the next Circus of the Spineless invertebrate carnival is coming up in early August on Roger’s Words & Pictures blog. If you have an invertebrate post that you’d like to submit, email a link to Roger by July 30th.
Tags: Yellow Bear, Virginian Tiger Moth, Spilosoma virginica, caterpillar rearing