Pig wool (fur) was a very important dubbing material, right up to the end of the 19th century, when it was superceded
by seal's fur. There is still a source for it in the USA.

Have a look here - http://www.dtnicolson.dial.pipex.com/page102.html

These are the type of Salmon flies used in Scotland before the introduction of all the exotic feathers and furs.
Which was done to sell flies to the English Tourists.
The above flies caught just as many Salmon and probably still would, were dressed and used by the locals around the Clyde and Tweed.
Remember every cottager kept a couple of pigs in those days.