The Forgotten Terrestrials

By Jeff Morgan

Anglers often have preconceived notions of the term "terrestrial." For years, terrestrial was synonymous with grasshopper --patterns had to end with the suffix "-Hopper" to fit the genre.

Many anglers have now expanded their definition (and fly box) to include ants and terrestrial beetles in their arsenal. However, to match these three groups of insects only scratches the surface of the terrestrial segment of the trout diet.

Professional studies of trout diets have proven that anglers needlessly limit their scope of terrestrial imitation. On average, beetles and ants each contribute about 25% of the terrestrial diet of trout. The much-imitated grasshopper may contribute another 5-10% of the total. What about the other 40-45% of the terrestrial diet? This is usually a smorgasbord of insects that are locally or regionally important. Inchworms, spruce moths, cicadas, bees, wasps, leafhoppers, aphids, terrestrial spiders, terrestrial midges and other Diptera can all show up at high densities in stomach samples.

It is this variety of terrestrials that makes attractors so effective. If trout eat 20 different terrestrials a day, that green Humpy is bound to approximate one of them.

But what if we set out to actually imitate some of these foods instead of relying on general attractors? You would then have a fly that worked when fish are not picky, as well as a pattern that will fool the toughest late-summer sipper.

Inchworms

Inchworms can prove a critical part of the early summer trout diet on streams that are shaded by trees. One study of a small British Columbia stream proved inchworms to be twice as important as any mayfly over the course of the summer. Another study in Colorado rated them the second most important terrestrial behind ants.

I recently fished several streams in Pennsylvania where people regularly referred to the "Inchworm Hatch."

When you consider inchworm patterns can be kicked out of the vise at the rate of dozens per hour, there is no excuse not to pack a couple.

My basic inchworm pattern is simply chartreuse deer hair on a hook. It is important to use a light-wire hook to allow for optimal floatation. With a regular-wire hook you would have to pack on so much deer hair that your imitation will look like a neon cocktail weenie.

It's a good idea to carry three colors of inchworms--chartreuse, tan, and bright green. Trout turn picky on inchworms, and you'll curse the fact that you didn't take an extra ten minutes to churn out a wider spectrum.

Foam can be used as a viable alternative, but I have found most colors too yellow or too green to imitate the natural.

Leafhoppers

Another important food is leafhoppers. Leafhoppers are small bugs that share grasshopper habitat as well as brushy or willow-lined banks. They hop around just like a grasshopper, and routinely fall into the water near the shoreline. The only difference is that leafhoppers aren't as affected by the wind as grasshoppers, as they rarely uses their wings.

My basic leafhopper imitation is easily constructed with limited materials. I use bright dubbing for the body, raffia treated with Flexament for the wing, and a couple of strands of bright chartreuse deer hair for legs. This pattern, if tied thin, can double as an excellent imitation of little green stoneflies . It also can double for a cluster of aphids, which compose a surprisingly large amount of the trout diet on small streams near clearcuts and gardens (aphids love the young saplings present in both environments). The bright green color of this fly makes it easy to see despite its small size.

Terrestrial Midges

My favorite terrestrial this summer has been an imitation of large terrestrial midges. The British have long imitated the Bibio, Duck Flies, and Hawthorne flies--all semi-aquatic relatives of midges that in their adult stages are a husky size 8 or 10.

We have large midges in the West, as well as an army of insects that look close enough to a big midge to make an imitation worthwhile.

The Bibio has a unique footprint on the water, one that makes it both a good floater and a good imitation for picky fish. The hackle is simply wrapped around a post of foam, which is pulled over the top, tied down, and trimmed to leave a small head behind.

The body can be dubbed or foam, but I prefer pheasant tail fibers. Black, natural brown, and olive pheasant tail can all be used to create a number of different body colors. The wing is traditionally elk or deer hair, but I like a treated raffia wing. It looks extremely natural and its shininess of the wing makes it more visible on the water.

The virtue of this imitation is the variety of insects it can cover. It may look like a big midge, but it also looks like a dark stonefly , wasp, adult cranefly , or even an emaciated cricket or grasshopper .

Don't shy away from size 8 or 10 imitations. It excels in these large sizes. Over the course of this summer in Yellowstone, I have found that a size 10 black Bibio has consistently outfished ant patterns for stubborn trout during non-hatch periods.

Patterns

For tying instructions, click the links below.

Falling Ophelia
Leafhopper
Bibio

Jeff Morgan has written many articles for Westfly, mostly on entomology and fly tying. He is the author of An Angler's Guide to the Oregon Cascades and Small Stream Fly Fishing.