Actually, believe it or not, this brilliantly colored, daytime active, thin bodied insect is a MOTH, the adult of the Ailanthus webworm, Atteva punctilla. The Ailanthus webworm is a sub-tropical insect that has spread north following the introduction of an "alternate" host plant, the introduced invasive species Ailanthus altissima, that has spread throughout North America. (Since the Ailanthus tree is not native to the Americas, while Atteva punctilla is, we can say that the moth has "adapted" a new host.) Further, Atteva punctilla is not adapted to survive cold winters, so apparently a population flies north each year to seek the abundant leaves of the Ailanthus trees. Since Ailanthus is generally considered undesirable (it has bad habits, like spreading into a huge thicket by runner roots, and producing a toxin that interferes with growth of other plants in its vicinity), the Atteva punctilla might be classified as a beneficial insect, although it doesn't do enough damage to seriously impact the Ailanthus. There are hundreds of images of this tiny but photogenic insect on the web. Here are a few: http://www.bugguide.net/node/view/1762 http://entweb.clemson.edu/museum/moths/local/moth16.htm

I'm having the exact same problem! I have noticed them twice now! Each time I inspected the whole tree thoroughly, and found a small group of these "bugs" at the end of a branch eating away, starting with the leafs at the end of the branch, and working their way towards the tree trunk. When I grab the branch to inspect it, I notice the little caterpillar-looking things have 2 or 3 legs on each side of their body, and only on the from 1/4 of their bodies. They seem attached to the leaf with their short legs and then they lift up the back 3/4 of their bodies in the air. What are these things and how do I get rid of them? Each time I have cut the small branch about 3 inches back from where they were and have thrown them in the garbage both times. What is a more permanent solution and where are they coming from? Any info would be greatly appreciated. Jen from the northern, Washington State coast.

This guy appears to be a Yellow Striped Armyworm, a common caterpillar with plenty of variations of color. Here is a link that might be useful: Click for comparison

Is it one of the tussock moths? There are more than one if this isn't the exact one. PJ Here is a link that might be useful: