DF8. The Blue Dun Dry Fly

THE BLUE DUN FLY PATTERN
This pattern has taken many trout for me, particularly early in the season.  Trout have a great liking for this little fly. It is commonly believed that it hatches only on wet, windy days. This is not true as I have seen numerous hatches in calm warm conditions. It is easy to spot as it is the only upwinged fly that has such an overall dark body color. It hatches from early to late summer. Peaks may occur in May and at end of summer in September. It emerges on the surface in open water during the day in irregular, but sometimes prolific, hatches. The Blue Dun generally is not an evening fly thankfully as trying to imitate such a small dark fly in failing light would be a headache and impossible to see on the surface.. They tend to swarm during the day. Mating and egg laying also often takes place during the day. 

In Britain this pattern is used to imitate the Iron Blue Dun. This fly is found throughout the British isles and is known by various different names such as Dark Watchet, Little Purple, Iron Blue Drake, Little Dark Blue or Little Dark Blue. The strange thing about this fly is that it undergoes a second moult in its winged stage and therefore a slight color and shape change during its life span. The dun is a poor flyer after it emerges. It is vulnerable to fish and birds so it normally rests for several hours or if the temperatures are low, over night on riverbank vegetation, shrubs or trees. When you are walking the riverbank it is always a good idea to turn over leaves and look in spiders webs to see what has been hatching. 

The last three segments of the male's abdomen in it's mature state turns a reddish brown whilst the rest turns a lighter pale colour. This is why you will see some patterns for sale with a small red abdomen. It is the egg laying female that is mainly eaten by fish and should by on the end of a fly fisherman's line most of the time not the male. Having completely dried out and rested after moulting you will see the males take to the air and swarm near the water. The females fly through the top of the swarm where they are clasped by a male and mating takes place on the wing. When they separate the female returns to the water and flies upstream prior to egg laying. She crawls underwater to deposit her eggs in the substrata. many females get trapped in the water surface tension when they return up to the water surface. Even those that manage to get airborne again fall exhausted back onto the water as spent spinners. They are then eagerly taken by hungry trout. 

The amount of eggs that are laid depends on the size of the female which varies from species to species and time of year. Females hatching later in the season are normally bigger than those in the cooler months. Some of the larger females can carry over 2,000 eggs. This fly falls within the insect family grouping called Ephemeroptera. I hate these long latin names, don't you? This family or order is subdivided into eight different groups. One of these groups goes by the name of Baetidae. It contains nine different individual insects. Two of them look so similar that to the naked eye you could not tell the difference. They are Baeties niger and Baeties muticus.  To you and me the Iron Blue Dun. The Baeties niger is normally found in Central and Southern England Chalkstreams, where as the Baeties niger is found all over the UK preferring faster flowing rivers with gravel beds 

DRY FLIES
The dry fly is designed to float on the surface of the water. To prevent it sinking, water repellent hackles are wound around the hook to distribute the weight over the surface of the water. The hackles also simulate the legs and splash of an aquatic or terrestrial insect trapped on the water surface. Most Dry flies are deceivers designed to imitate a specific natural fly like the crane fly, ant and hopper series of flies. Other flies like the Adams are more general designs that are just intended to produce an edible looking fly.

Dry fly fishing has always been regarded as the supreme art in fly fishing circles. Accurate presentation of the fly can be essential. Trout will rise to a variety of natural flies but as far as the dry fly fisherman is concerned the mayfly hatch has to be the favored time. In almost all instances where trout feed on drowning insects the rule is not to move the fly. An imitation is far more likely to succeed if it is cast out and then left. So long as it is cast in the right spot.

The color of the fly is always important when matching the hatch, then size is the next important decision. The artificial fly does not have to be a precise imitation of the natural insect, but what is important is how and where it is presented in relation to the depth of water. This includes the height at which the fly floats above the surface of the water. Some fish will greedily take flies that are floating in the surface but ignore flies that are floating above it and visa versa depending on the conditions that day. Use your eyes to see which natural insects the fish are taking. A high-floating dry fly will have more chance of being taken on a bright day because of its visibility, but if it does not dent the surface film on a dull day it will be less effective. A fly floating in the surface on a sunless day leaves a much more visible halo of outlining light which surrounds it.

Always try and get the leader immediately in front of the fly to sink under the water as this makes it harder for the fish to spot. This can make the difference between a blank day or one with lots of action. When putting on floatant make sure you keep it off the leader. This is a common mistake that can affect your fish catching chances. Degrease the front 10 inches. Do not try and fish this pattern downstream as it will drown. Fish it upstream and look in front of you for where the fish are rising for the natural insect. Be observant. If the trout start to dine on spent spinners rather then duns consider changing fly patterns. 

MAYFLIES
Some adult mayflies hatch throughout the year but other species hatch only during certain months of the year. The term Mayfly applies to all members of the order of insects not just those that emerge in May. There are hundreds of fly patterns tied to imitate the many different mayflies and stages of their development. The natural insect belongs to the group of insects called Ephemeroptera. Ephemeros means 'lasting a day' and peteron means 'a wing'. Mayflies have cylindrical bodies, slender legs and two pairs of veined wings which are held vertical when at rest. They are found all over the world and are commonly called up-winged flies in some areas. The adults do not feed and live for only a very short time: most less than a day and some only for a few minutes. 

The aquatic Mayfly nymphs moult anything from 12 to 50 times and take up to two years to reach adulthood. In any square yard or meter of a stream there may be a few hundred to many thousand mayfly nymphs. They are an important part of any predator fish's diet. The fully grown nymph swallows air and floats to the surface where it emerges into the subimaginal stage. The Dun sits on the water surface for a few seconds after hatching to enable the blood to pump up it's wings and for them to dry. The colder the weather the longer this takes. It is very vulnerable to attack at this time from under the water surface. On windy days, gusts can topple over the drifting duns and drown them. If you cannot see any rises for surface floating duns during a hatch on windy days the fish are feasting sub surface on the unlucky sinking drowned duns as well as the emerging nymphs. Try using a partridge and Yellow Soft hackled spider wet fly, Gold Ribbed Hares Ear Wet fly, Blue Dun or Light Cahill wet fly to imitate drowned duns, depending on the local insects body color that can range from pale yellow, olive to tan. Wing color also varies throughout the world from pale gray to pale yellow. I often fish these wet flies on a dropper about 18 inches behind a dry fly. The soft hackle or wet fly imitating the drowned dun often catches the fish when nothing else works.

If the drifting newly emerged duns have not been eaten by a fish during this vulnerable time, they fly off and hide on the surrounding vegetation. Within 24 hours the duns molt into spinners and and are ready to mate. Mating swarms are formed by the males to attract females. They also occur at dawn or dusk to reduce the chances of single insects being taken. When a female flies into the swarm she mates with a male. The males fall onto the water spent and drown. They are known as 'spent spinners'. The females return to the riverside vegetation for a short period whilst the eggs mature. When the eggs are ready the females fly out over the water, dip into the water, lay their eggs and then fall into the water spent.  Some females species swim down to attach their eggs to submerged vegetation or objects. Others just land on the water surface making tempting targets for hungry trout. Try and scoop up a natural spinner floating dead in the water surface and match the body color with a parachute dry fly like a Greenwells, Tup's Indispensable or Gold Ribbed Hares Ear Parachute.