There are some kind of worms on my pine trees.?

Question

Its like they wrap themselves on the leaves and if you look at my pine tree, you could see them moving down or up with a thin string. The little worms are kinda black. Can someone help. There destroying my trees

Answer 1

is it these?...

http://gardenauthor.blogspot.com/2008/05...

or these?...

http://woodypests.cas.psu.edu/factsheets...