Thursday, June 16, 2011

What are all these Caterpllars?

Posted by Kirk
I've been noticing a lot of caterpillars this spring. Specifically, this little guy on the left.

I found this one on the 1.1 billion year old basalt formations at Interstate Park along the St. Croix River. I was there to take some photos for a geology class I'm teaching. This guy happened to be next to a nice amygdule, or a mineral filled lava bubble. I'd seen this same species of caterpillar at work, at home and at several parks. What was it?

The day after taking this photo a volunteer at work mentioned an interesting caterpillar in her yard. It was the same species. It didn't take more than a minute to look it up and see what it was.

These are Forest Tent Caterpillars. They are more prolific in some years than others which might explain why I'm seeing so many. The Forest Tent Caterpillar should not be confused with the very similar looking Eastern Tent Caterpillar that is responsible for the large silk "tents" in the woods. Forest Tent Caterpillars build a silky sheet for molting rather than the "tents" of the Eastern Tent Caterpillar. Eastern Tent Caterpillars rarely leave their host tree while Forest Tent Caterpillars wander all over the place.

Forest Tent Caterpillars have a broken yellow line down the length of their body while Eastern Tent Caterpillars have a solid yellow line.

They are fascinating creatures. Is anyone else seeing larger than usual numbers this year?



Unknown said...

My friend and fellow blogger Mary Schier of Northern Gardener magazine and just published an article on Northfield Patch about the Eastern Tent Caterpillars being particularly prevalent this year