There are currently lots of these cobwebby things in the trees we have all over Austin, but they do not belong to spiders. They are made by webworms
. Inside those nests the worms are hatching and eating the tree before turning into moths and flying off to do the same thing again. I think they look pretty weird and Gothic. Don't walk under one in case it breaks and all the worms fall out and land on your head (only joking, that probably can't really happen, maybe).