From James E. Leisenring’s book
The Art of Tying The Wet-Fly
In his book, Leisenring lists seven nymphs.
The list appears to be based on British patterns.
For instance 1 is derived from the “Tup’s Indispensable”, usually fished as a dry fly.
Number 2 is less certain as there are many American versions of the “March Brown”.
Number 3, the “Half Stone” is a very well known dry/wet fly from the west of England and is dressed with cock hackle.
Numbers 5,6 and 7 are all dressed with cock hackle.
Numbers 4.5,6 and 7, are all based on G. E. M. Skues patterns,
Which is not surprising as Leisenring had a considerable correspondence with Skues.