The Beadhead Nuke Egg Fly Pattern also known as Nuclear Egg is an evolution of the original Glo Bug. It is tied loosely around a hook giving the appearance of a real egg when wet yet translucent under water.
It is very popular for Grayling, Steelhead, Salmon, Rainbow Trout etc. In fact, many fish love eggs and will nimble at them indiscriminately making this fly very popular.