We know this fly, without the beadhead, originated in England some say as far back as 1600. Modern references 1800. It seems to fit in with a large selection of subsurface trout food being grey Mayfly nymphs and grey Stonefly nymphs to name a couple. Kiwi fishers have a fascination for all types of grey nymph patterns and in particular beadhead flies. It can also imitate a drifting grey caddis pupa. Don't get caught without one in your arsenal of flies.