August is a month between many of the year’s best hatches. The prolific mayfly hatches of spring and early summer are history, as are the big stoneflies - golden stones and salmonflies - that grace the early days of summer. Caddisflies can still put on a good show this time of year, and of course there are terrestrials, especially hoppers, that excite trout and anglers. But some interesting insects periodically show up. One mayfly in particular appears in mid summer, often in small numbers, but it’s always been one of my favorites. It’s fresh in my mind since Dave Hughes and I ran into one on a recent fishing trip in Eastern Oregon.

This mayfly goes by numerous common names including: Great Blue-winged Red Quill, Great Brown Spinner, Great Red Quill, and Sawtooth. Many have “great” attached to the name, which could indicate it hatches in great numbers, or that it is of great size. Well, in this case it is size that accounts for their greatness in name, but when they are on the water, even in moderate numbers, you can have some great fishing.

So who is this mayfly? It’s Timpanoga hecuba hecuba. Cool name, and the nymph is just as cool looking (see nymph photo). This is a large mayfly with the nymph reaching three quarters of an inch long, and duns and spinners are that long not counting their tails. As you see in the photo of the nymph they are not your typical looking mayfly. They belong to the family Ephemerellidae, which are considered crawlers, but this species is flat as any clinger nymph. The first set of gills are also enlarged - called operculate - and do a good job of covering the remaining sets of gills. This provides good protection from silt that might settle on and degrade the function of more exposed gills. For this reason Timpanoga nymphs do well in slower and siltier streams than many other mayflies. As a result the nymphs are found in a wide range of streams, from small coastal creeks (the subspecies Timpanoga hecuba pacifica lives in coastal streams of the Pacific Northwest) to large valley rivers in the Rockies. Some of the best populations occur in the slower moving sections of the Yellowstone River in Yellowstone Park.

When Dave Hughes and I did our book Western Mayfly Hatches, we didn’t have and couldn’t find a good photo of a Timpanoga spinner. That changed on our recent Eastern Oregon fishing trip where the attached spinner photo was taken. What surprised us was the way we found the spinner. We were camping along this small mountain stream and had just started to eat breakfast. Dave went over to the cooler, which was sitting just outside the mosquito tent setup over a couple small tables, and there upside-down on the cooler lid was this spinner, in perfect shape no less.  Without knowing for sure, but suspecting it was Timpanoga, we set up our cameras with macro-lenses and began shooting photos. Later at home I confirmed it was T. hecuba hecuba. Besides its large size and reddish brown color, a key feature confirming it as Timpanoga is the gill remnants of the nymph left on abdominal segments 4-7 (see photo).

Why would a large mayfly spinner show up in the morning out of nowhere on the lid of an entomologist’s cooler? We can’t explain it, but certainly appreciate its presence.

By the way there wasn’t any hatch of Timpanoga that we saw during our time fishing this little mountain stream, which makes the presence of this lone spinner on our cooler all the more inexplicable. You can find a complete description, plus patterns and tactics for fishing the Timpanoga hatch starting on page 150 in Western Mayfly Hatches.

May Timpanoga grace you with its presence on your next fishing trip!