The blood dot egg is a yarn fly that imitates trout and salmon eggs. When the yarn makes contact with the water it becomes a little translucent and looks even more like a real egg than it does when it is dry. The dot provides contrast and represents a developing fish fry. All sorts of fish eat eggs but these flies are especially effective for trout and salmon. Both wild fish and stocked fish will hit these flies even when fish are not actually laying eggs.