In late summer and autumn, skilled fly rodders in Maine often choose two vastly different categories of flies for trout: large, dark nymphs and baitfish imitations; or micro-mayflies and caddises to imitate specific bugs.

Big patterns usually fall into searching-type flies that require less attention to detail, just generic, juicy-looking mouthfuls, but the micro-flies often require matching natural insects in size, color and silhouette.

Whatever the choice, consistent success requires knowing how to present each fly correctly. Fly fishers competent with nymph or baitfish imitations concentrate on depth, retrieval speeds and tactics — say fishing near bottom with long, fast strips or shorter, slow ones.

The plan often starts with ultra-fast stripping with streamers and bucktails and slower retrieving for nymphs — varying the depth until finding the trout’s preferred level in the water column. Fly fishers often time the descent of the fly with a watch until catching fish, and then they key there.

Matching floating insects often calls for dead-drifts with imitations, and they must move at the exact speed as the current. Hatch matching can get darned technical in the normally low autumn water.

This month, fly casters with a scientific mind notice ultra-active, fall micro-hatches of blue-winged olive or all-cream mayflies and small, tan or rust caddises in varying sizes or shades, just to name common options.

Serious fly fishers identify each insect (or baitfish), so they often rely on fly-fishing entomology or ichthyology books. After identifying the forage item, they read up on how the species behaves beneath the surface. Then, they duplicate the movement of the critter.

With newly hatched surface bugs, folks imitate movement or lack of movement. Our eyes tell us how these insects behave on the meniscus — motionless dead-drift, fluttering, skipping or so forth. We then duplicate the natural insect’s movement with a fly that matches size, color and silhouette.

Sometimes, serious fly rodders tie flies that imitate insects they have never seen. Here’s a perfect example from my youth:

One winter in my 20s, I studied entomology books aimed at anglers and occasionally tied imitations for insects that I had never seen on the water. My fly selection grew from those white-season tying marathons.

One January, a mayfly dun imitation in Art Flick’s “Streamside Guide” caught my eye. Back then, we called the natural fly Potamanthus distinctus, a somewhat common species in Maine. (Today, that name has changed to Anthopotamus distinctus.) A Cream Variant or the more realistic cream Compara-dun imitated the bug well enough to fool trout.

Anyway, back then, other than in a photo in a book, I had never seen this insect, but the picture and description of its behavior gave me all the information needed to fish the pattern successfully should we meet.

The newly emerged P. distinctus floated dead-drift on the surface before flying off, so matching it required casts quartering across and upstream and letting the imitation drift naturally downstream over fish.

The next June, this insect was hatching on a tiny river, a huge thrill, because I knew what fly worked and how to fish it. My book knowledge and newly tied imitations gave me several excellent days of dry-fly-fishing.

Incidents like that throughout my life have given me ample encouragement to study insects because wrestling with good-sized salmonids creates high drama on a wispy rod with a hair-sized tippet.

Lots of wags joke about fellow fly rodders studying Latin names, but lots of insect designations came from Greek. Even more intriguing, entomologists made up many Latin names, so readers won’t find them in Latin dictionaries. In short, scientific names for bugs prove less geeky than folks might think.

I studied Latin in school, so I learned in my early fly-fishing days about made-up words. Curiosity drove me to my Latin dictionary to look at word definitions, and it wouldn’t have many of the Latin words for insects.

When folks find the specific genus and species for a mayfly nymph in rivers, they can see if scientists have classified it as a bug that 1. clings on bottom, 2. crawls around there, 3. burrows in mud, or 4. swims.

This knowledge of flowing water tells us to dead-drift clinger or crawler nymphs. Why? The current sometimes washes them from bottom, and they float downstream until they can grab a rock, gravel, submerged wood or underwater weeds. A freely floating fly moving at the same speed as the current proves deadly to imitate larvae, drifting in the current.

For swimming nymphs like Isonychia bicolor or most blue-winged olives, a presentation quartering-downstream-and-across followed by an arc-like swing in the current puts the fly downstream. Then, inching the fly back against the current imitates a swimming insect. Burrowers also swim well enough when hatching and respond to the downstream presentation. 

Ken Allen of Belgrade Lakes is a writer, editor and photographer. He can be contacted at:

[email protected]