What are these things on my spokes?

Image: https://cimg5.ibsrv.net/gimg/bikeforums.net-vbulletin/900x1200/img_5172_3fec308a0e76a78aff28a837c092b96e4496188e.jpg Image: https://cimg6.ibsrv.net/gimg/bikeforums.net-vbulletin/1200x900/img_5179_debbc18187541a232be013a0fa6f95bc42acea62.jpg Image:...