Facing a weekend with apartment to myself, I did what I suspect many fly fishermen in the Northern Hemisphere are doing: tying flies in preparation for the rapidly approaching season. As one tier said to me recently, “If I don’t start tying now, my boxes will be empty!” While that’s not entirely true — fishermen always fear a scarcity of flies, but rarely face it — the feeling is accurate: with the days warming up, it’s now a race.