The green beetle fly represents the manuka beetle. Tied with deer hair this beetle is everywhere during Nov/December in NZ and this fly is a big fish taker. The fly is supposed to sit in the surface of the water as a drowned beetle. You need this in your fly box for late spring and early summer.
Some years ago before the pine forests on lakes like Taupo the water surface often was a murky yellow colour for as far as the eye could see with drowned Manuka beetles and so many were on leaves that they would break off into the water. Trout would break the oil slick like surface to sculp away at beetle.