The No-See-Um is exactly that…but only to the fisherman. The fish do not have a problem at all! This thin-skirted fly with mirage material and high tech beads create a full, color-changing quality in the water. This No-See-Um is a deadly fly wherever it is fished.   Again, beware of the imitations.  A number of companies have attempted to copy the No-See-Um and have used the name as well.