Hendrickson

Telling it apart

• Size 12 to 14, an 8–11 mm body.
• Three tails — which is what separates it from the Quill Gordon, which has two.
• Slate-grey wings held upright, without strong mottling.
• The female's body runs pinkish-tan to olive; the male is darker, a red-brown.
• A stocky crawler nymph, on gravel and in leaf packs.

Two fly names, one insect

The Hendrickson and the Red Quill are sold as two separate patterns and fished as two separate patterns. They are the female and the male of the same species. The sexual dimorphism in Ephemerella subvaria is pronounced enough that tyers named them separately before anyone worked out they were looking at a pair.

This matters on the water: both come off together, and on a given day trout can lock onto one and refuse the other. If refusals are piling up on the lighter fly, try the darker one before you change size.

Why the afternoon — and why that changes later

In May the water is still cold. Emergence triggers somewhere around 10–13°C, and that threshold is only reached at the warmest point of the day — mid-afternoon. That is why the Hendrickson comes off between 1 and 4 p.m., and why a cold day compresses the whole hatch into a single hour.

The same logic explains why hatches slide toward evening as the season goes on. By June and July the water clears the threshold by morning and stays above it all afternoon, so the comfortable window moves to dusk. It was never the hour — it was the temperature.

The dun that cannot leave

In 11°C water a dun takes far longer to dry its wings than it does in warm July water. So it rides, sometimes for tens of metres, in plain view.

That is precisely why the Hendrickson is such a good dry-fly hatch: not because there are more insects than later in the year, but because each one stays available for longer. It is also why the emerger, stuck in the film, often outfishes the perfectly tied dun.