Newbury's Angling Arts

Taxonomists have divided the known biological world up into eight categories from domain, kingdom, down to genus and species. For a fly angler wanting to know how to choose the right fly, it is essential to know at least the family orders of the three primary aquatic insects that make up the bulk of a trout's diet. Familiarity with these three insect families is a must when choosing the right fly.

As the name suggests, ephemerella, mayfly’s are short-lived often less than two days. However, it is only the winged adult phase that mayflies only live this brief time. Nymphs of mayflies can live up to a year or longer during the sub-adult larval phase AKA nymph.

Drunella grandis nymph

Mayflies have an incomplete life cycle with only a larval and adult stage and lacking a pupal stage. However, mayflies undergo two further stages of reproductive maturity with the first adult phase called the sub-imago or dun, the winged but not yet sexually mature and the imago stage or spinner, the final reproductive stage in the insects' life cycle. As mayflies emerge from the water, they will gather in and around the riparian canopy to undergo one more molt to become imagos or commonly called spinners and mate. Essentially, the dun stage is only used to transport the nymph from the bottom of the stream to the tree canopy to mate.

Historically, fly fisherman favored fishing during a mayfly “hatch,” the transitory period between nymph and dun and imitate a dun (sub-imago) with a dry fly. When the nymphs transition into duns, a period of predatory vulnerability exists while the emerging insect floats on the water surface. Depending on environmental factors such as weather, water temps, cloud cover all play a role in how long insects may drift along before taking flight into the bankside foliage. These extended drifts make for rewarding dry fly fishing opportunities when you happen upon it.

Drunella grandis sub-imago

Today’s anglers know that a dry fly hatch can be a short and unpredictable event with being at the right place and right time essential for dry fly fishing success. Fishing with nymphs offers anglers an unlimited opportunity to present a food item to a fish during the rest of the day. Famous rivers that were historically known for having regular daily hatches are seeing less reliable hatches and dry fly fishing taking a back seat to fishing nymphs or emergers. Many factors may be conspiring to the unreliability of daily hatches such as increasing angler hours/visits and climate change. Heavy angling pressure may be driving the fish from surface feeding and solely concentrating on nymphs and emerging duns sub-surface.

The following mayfly nymph types should be considered when selecting or tying our flies.

Minnow Shaped Nymphs

Baetis nymph

Minnow shaped nymphs such as Baetis species are agile swimmers. Baetis actively swim to the surface and back to the bottom repeatedly for several days prior to emergence. When tying patterns that imitate baetis nymphs, bear in mind the shallow taper and slim body. Keep these nymphs thin and streamlined.

Common Genus:

Ameletus

Baetidae

Leptophlebia

Paraleptophlebia

Spiney Crawlers

Members of the crawler group are very active and frequent swimmers but prefer to remain amongst the cobble. Many begin the emergence process underwater where a spot of color enhances the fly and rapidly swim towards the surface.

Common Genus:

Ephemerella

Drunella

Clinger - Crawlers

Clinger nymphs, as the name suggests, cling firmly onto rock and woody debris. It is now thought that the shape of clingers is not only about remaining firmly attached to the substrate, but rather, the thin profile allows them feed in the interstitial spaces between rocks that other nymph shapes cannot exploit. I suspect the large gills also aid in breathing within those murky, silty spaces.

Of all the members of the EPT group, caddis are the only family to undergo a complete life cycle: larva, pupa, and adult. The pupal form is the transitional stage between either a sheltered dwelling of free-living caddis larva and the winged adult. Free-living caddis larva only build protective shelters of debris or stones that they seal themselves inside during pupation. Caddis pupa are only available at the time of emergence and in most cases, emerging pupa is the most vulnerable stage of the life cycle that available to trout.

It has long been debated the theory that caddis inflate their exoskeletons with a gas bubble to emerge to the surface. While I have not seen this phenomenon in person, I have seen tiny flashes of light near the surface of the water like that of the paparazzi shooting a movie star walking the red carpet. I have surmised that I was witnessing the glints of light as caddis emerge encased in this so-called gas bubble. Because of this phenomenon, I fish with caddis emerger patterns that imitate this gas bubble to some degree at or very near the surface instead or presented deeply. When fishing deeper in the water column, I use much less flashy, more opaque caddis pupa imitations because they have not yet begun to exhibit this gas bubble.

I have observed several caddis species whose exoskeleton would exfoliate in the process of emergence. The chitin of the pupa would be somewhat transparent allowing the more colorful adults’ abdomen to show through. Patterns such as my Lucent Sedge imitate this occurrence. Either way, I strive for a bright yet transparent effect when designing caddis pupa patterns.

To give credit elsewhere, I once heard another fly fishing guru advise to use duller patterns deep and flasy patterns higher in the wayer column to match this natural phenomenon.

Free Living Caddis

Caddis larva are broken down into three distinct groups, the free living, net spinning and case/shelter building groups. Each of these groups have distinct behavioral characteristics important for the angler and fly tyer to understand. Free living caddis are predatory in nature, do not build shelters and crawl around the rocks in search of other macro invertebrates in which to feed upon. Net building caddis spin funnel shaped webs and feed on detritus filtered from the current captured in the nets that they construct. Shelter building caddis build protective shelters that they carry around with them as the crawl amongst the cobble feeding on the bio-film that grows on the rocks.

It is interesting to note that free living caddis larva species emerge in small numbers throughout the season and are always available as opportunistic prey items throughout the day and long into the evening. Emergence activity of the free living groups will typically be in small but predictable numbers all season long. This makes them a top choice for the angler to imitate when no specific hatch activity can be observed. I generally prefer to start my angling day with a heavy Czech nymph probing the depths hoping to take advantage of opportunistic feeding activity and switch to a caddis emerger pattern when I actually detect emergence activity.

Common Genus:

Cased Caddis

Some smaller shelter building caddis use a survival by numbers strategy for success. This means that they are typically found in very large quantities and emerge en-mass to avoid being heavily preyed upon in order to propagate the species. A very well known instance of this phenomenon is the Mother’s Day Caddis hatch of Brachycentrus. This hatch usually only lasts about 10 days or less just prior to runoff season. Clouds of caddis fill the air overwhelming predators both above and below the water through sheer confusion and overwhelming numbers.

Anglers should practice the habit of turning over rocks and observing the general size shape and color of the caddis found. Kick net sampling is another effective method of gaining an understanding of the diversity of caddis groups that are present in your water.

Common genus: