On August 28th, I found a White-marked Tussock Moth caterpillar slowly descending a tree in the Ile Bizard nature park near Montreal. It paused beside a raised piece of bark and stayed motionless for a long time which allowed me to get many photographs of it. I find it a particularly striking caterpillar and was excited to find it.
Then on September 15th, I returned to the park and whimsically decided to visit the same tree to see if, by chance, the caterpillar was still there. Instead, in the exact place where the caterpillar paused, I found an odd looking cocoon with black hairs sticking out and a frothy substance stuck to it. I decided to check the Internet for images of the cocoon of the White-marked Tussock Moth and was surprised to learn that it was indeed the cocoon of the very caterpillar I had seen earlier!
I also learned that the caterpillar was a female who, when she emerges as a moth, lays her eggs on the cocoon which are encased in a foam which hardens and allows them to over-winter. She must attract males soon after emerging, then mates, and lays her eggs in a very short time frame. Another fascinating fact is that she has rudimentary wings and cannot fly.
Since reading that the moth stays in the vicinity of the cocoon, I was disappointed not to find her on the tree but I will look for these cocoons next year and hopefully find a moth then.
I also found another cocoon in a different park a few days later, but alas, no moth:
This link has more information and photos: http://www.abundantnature.com/