bow hair is the favorite food of carpet beetle larvae..
http://www.talkbass.com/forum/archive/index.php/t-352415.html
http://www.wikihow.com/Get-Rid-of-Bow-Bugs
http://www.johnsonstring.com/Bitten%20By%20Bug.htm
http://ezinearticles.com/?Whats-Eating-Your-Violin-Bow-Hair?--It-Might-Be-Bow-Bugs&id=2461787
http://www.bekkerviolins.com/drupal/comment/reply/241
http://www.bekkerviolins.com/drupal/sites/default/files/imagepicker/a/Albertus%20Bekker/CarpetBeetleLarva.jpg - here is the culprit
it leaves it's little exo-skeleton when it sheds it...vacuum these up@
http://www.theviolinsite.com/violin_care_guide/bow_care.html

they like wool, silk, hair,fur and natural and animal fibers.