The Black/White Spinner is a simple dry fly that imitates common mayflies emerging from the water. Fish this fly in slower-moving waters during mayfly hatches, especially in the spring and summer. They work best when tied in behind a dry fly with around a foot of light tippet. A dry-dropper setup is deadly in any trout river, especially when using a small spinner like this one. A row of these in your small dry fly box will do the trick for most hatches.