
Tried matches. The web would not light. At last I hit on wrapping pages of newspaper around the webs and setting them on fire.
After that was done I finally looked up the fall webworm, Hyphantria cunea. They weaken all kinds of deciduous trees by skeletonizing the leaves. Turns out that burning the bags, after wrapping them in rags, is a time-honored way of getting rid of them. The bags that can't be reached from the ground can be torn open with a stick or rake so that birds may come and feed on the webworms.