Here's how to tell the difference between ETC and the Fall Webworm , which is what these guys are:

The FW builds their nests on the ends of the branches rather than the angles and crotches of the branches. Also, the ETC outbreaks tend to occur much earlier in the season. The third identifying feature is that your caterpillars are much hairier than the ETC.

Luckily, there are many control measures that already exist in nature. If you disrupt their nests with a rake or pole or strong spray of water, they will become an easy meal for a wide variety of birds, spiders, anoles, lizards, and predatory insects. There are also myriad of parasitoids that will gladly use them as hosts.

Thanks, rhizo_1, for the additional info (the two types of nests, the timing of the nest), and for the reply on the Pests forum also.

I had been curious about those webs for some time now. Now I know!

An enemy of the tent catepillar and webworm is the brown thrasher. Brown thrashers will dine on these catepillars and feed them to their young.

Also, cuckoos love tent caterpillars. So good food source for birds.