About twenty years ago, I traveled with a friend to Junín de los Andes in the month of January and had some great fishing moments, but one of them really stuck in my mind. We got to the Aluminé river late and decided to spend the night there. The following morning I was just about to have some mate (classic Argentine infusion) as I watched some green stuff over some willow logs. I thought it was just some mate herbs people had left behind, but later on I realized that this green stuff were thousands of inchworms (the larva of many species of moths) that had fallen from the willow trees.
I then took a handful of these worms and began dropping them on the water. I saw that some sank pretty fast and others remained at the surface, floating in the current. This depended on how they fell on the water, breaking surface tension or not.
These certainly were prime trout food in that month, and though we had seen many flies tied to resemble these beings and heard stories about how effective they were, we had no imitations in our boxes or tying materials to make some of them.
Many years passed from that day, but in the meantime I had hundreds of requests to tie these little worms, and using all kinds of materials: vernille, foam, dubbing, swannundaze, larva lace, vinyl rib, and more. But it was in the summer of 2006 that I got back to Patagonia, in the warm months of January and February. Then I got to know that these were really effective flies. I made a badly crafted imitation, a chartreuse EVA rubber strip tied at only one point on the hook, which looked like a V. Still, I had great results with it.
Then, back in 2007, I was fishing with another friend at the Malleo river, where we caught 10 rainbows and a perch just by letting some of these flies sink between two willow trees. Small trout rose to take the fly, big ones just ate the ones that sank when these drifted close to them. We set a small weight on the leader about 40 cm away from the fly, and let it sink to the bottom, where the big trout were holding. These would cruise to take the fly as it drifted by them.
These spots, at the edge of the willow trees, had rising trout most of the time because the wind made worms fall off them. Then one should place the fly close to the tree base and try to make the fly drift with no drag. Many times the response was immediate.
Although there are many patterns that imitate inch worms, I will describe the one we used in this case. Some may say it´s too simple but I´d say it´s a must when fishing in January and February in waters with willow trees in its shores.
Hook: size #12 to #14, dry fly hook (TMC 100 or similar).
Thread: 8/0, green.Body: foam strip. Cut with scissors. Tips should be rounded with a lighter.
Tie the foam rubber strip with several thread turns at the same spot.
Keep doing turns until you reach the hook eye, these should be separated evenly.
Tie the foam strip once again with several turns at the same spot. The section between the two points should be let loose, so that it describes a curve.