MS6. The Light Cahill Mayfly Spinner

From the middle of May to September, depending on where you live, hatches of different varieties of light colored mayflies now commonly known as Light Cahills can be found. This is a recent collective common name that covers many groups of the Heptageniidae family of mayfly insects. In the 1880's a New York railroad worker called Daniel Cahill developed a fly that became famous all over America, the Light Cahill. When he wasn't fishing or tying flies he was a brakeman on the old Erie and Lackawana Railroad. It is a great general imitation of summer mayfly duns. Just choose the hook size and color to match your local hatch. It was originally designed to imitate a family of mayflies with the name of Stenonema. They begin hatching in late May and continue through June In smaller sizes the Light Cahill is a useful fly to imitate hatches of Pale Morning Duns, Pale Watery Duns, Spurwings, Pale Evening Duns and the Red Quill Mayfly. The Pale Morning Dun (PMD) hatch is normally in the summer and massive in numbers, triggering aggressive trout feeding. The hatch normally happens in slow, clear water. The PMD is normally best matched with a size 18 hook fly. The Red Quill mayfly is not as widespread as other mayflies but if they live in the river you are fishing, you will find that this fly is an important insect to have imitations of. The reason being is that they occur in large numbers when they hatch and these are the flies that the trout want. Hatches are normally in the afternoon.

Dan Cahill is also credited with the unscheduled stocking of some Eastern North American rivers and streams with Rainbow trout. The story goes that on one steamy hot summer's day Dan was working a Lackawana freight train north of Port Jervis.  The train's progress was blocked by a derailed work train. Part of the freight being carried that particular day was a large water container full of live stock rainbow trout. They were starting to cook. They would not survive the delay. Dan took action to save them from certain death. He talked his work mates into helping him carry them back to Calicoon Creek and let them go free.  It was almost a mile back along the tracks. Their offspring have eventually spread throughout the whole Delaware watershead.

Art Flick in his book "Stream Guide to Natural and their Imitations" said of the Light Cahill pattern, "To this date I have never met a fisherman who had fished any stream where trout could not be taken on this fly. It is doubtful if any fly compares with it in popularity, especially in the East."

Ray Bergman author of "Trout" in 1938 commented on the light Cahill, "If it was necessary to confine my assortment of flies to only two or three, this would be one of them." He stated that although it is particularly effective in Catskill waters and similar mountain streams it had served him well in Michigan, Wyoming and California. He said, it is a "killing fly."

CUSTOMERS COMMENT
I use these flies with success on rivers in North Georgia, Eastern Tennessee and Western North Carolina like the Hiawassee, Chattooga, Tellico and Davidson. They seem to work very well. The Light Cahill is easily my most favorite and productive fly. Frank Booth, Gainesville GA, USA

FAN-WINGED MAYFLY SPECIALS
This fly achieves deception not only because it looks something like the real thing, but also because it behaves so naturally, alighting gently onto the water like an egg laying spinner or a dun mayfly needing a second attempt to take off. Some anglers try this fly and hate it. They are casting it wrong. It is important to cast gently and that means not covering too much water with each cast. This pattern is deadly provided the hatch is on but not so profuse that the trout are too spoil for choice. 

A TROUT'S DIET - THE MAYFLY
Some artificial fishing flies try to imitate the fish's food at the different stages of an insect's life. A good example is the Mayfly. They all have upright wings and two or three long tails. There are five stages in the metamorphosis and life of the mayfly: egg, nymph, dun, spinner, and spent. Mayflies are commonly called 'up-winged' flies. They are recognized as being the staple diet of the trout. They are delicate insects with cylindrical bodies and two pairs of erect veined wings. Some mayfly species can be found at almost anytime of the year but others emerge only during certain times between the four month period from May to August. The term 'Mayfly' applies to all these species and not just the flies that hatch in May.

This group of fly fishing flies is tied to imitate the natural insects of the order Ephemeroptera. If you are saying that big word sounds Greek to me you would be 100% correct. 'Ephemeros' is Greek for 'lasting a day' and 'pteron' means 'a wing'. Most adults live less than a day and in some species they survive for only a matter of minutes. There are 2,500 species in the world: 46 in the UK, 85 in Australia and 611 in North America.

In a typical stream there may be a few hundred or a few thousand mayfly nymphs per square yard/metre. Mayflies do not have any defenses against those that prey on them. What they lack in defense they make up for in numbers. They are an extremely important element of all freshwater fish's diets. There are thousands of fly patterns tied to imitate these insects at the different stages of their development. There is a lot of folklore and fishing jargon surrounding these flies that confuses the beginner. The best advice when you first start fly fishing is to ignore it all. Stop trying to match the natural insect with an exact named representation. Unlike other insect groups mayflies all look very similar and do much the same as other mayflies. Keep a range of imitations in your fly box to cover the life cycle of these insects from aquatic nymph to the spent dead mayfly floating on the water surface. Use the one that looks most like your local flies.

THE MAYFLY 'NYMPH' STAGE
After hatching from the egg the nymph lives and feeds on the bottom. Some are eaten at this stage by foraging trout. Nymphs are also taken as they swim towards the surface. These can be found in ponds, streams, lakes and rivers. They vary in appearance depending on the habitat they have adapted to live in. Most have three tails. Some have long legs for swimming whilst those in faster moving water have short strong legs for crawling.

THE MAYFLY 'DUN' STAGE
At the surface the 'dun' emerges from the nymph stage as it sheds it's old skin. Although winged it is not yet sexually mature, and it must cast its skin one more time to become a spinner. Mayflies are unique in having a pre-adult winged stage. They are the only insects that molt again after they have developed functional wings. This stage is called 'subimago' but more commonly known to fly fishermen as the 'Dun' stage. The nymphs can molt between 12 to 50 times and take over 2 years before they reach the adult stage. Fully grown nymphs rise to the surface and molt into the 'subimago' or 'Dun' stage. This is the most dangerous time for any mayfly as they are easy prey for fish from below and dragon flies from above. To reduce the chances of any single animal being seen or eaten mass emergences take place at dawn and dusk. The dull colored and slightly hairy Dun subimago can be found fluttering to nearby vegetation.

THE MAYFLY ADULT 'SPINNER' STAGE
The final molt to the hairless, shiny-winged adult form takes place a couple of minutes after emerging or a couple of days after. The adults are known as 'spinners' and their main task is to mate in the little time they have left. Males die shortly after mating and the females die after laying her eggs. After mating the female drops egg masses into the water. Some species land on the water surface to perform this function where they are sucked up by hungry waiting trout. Other females enter the water and swim down to attach their eggs to submerged objects.

THE MAYFLY ADULT 'SPENT' STAGE
The dead and dying mayflies are called 'spent' spinners. They are easy prey for the trout.

FISHING WITH MAYFLIES
Mid spring is when you start to see the first hatches of mayflies as the temperature gets warmer. Look in the shallows as the water will be the first to reach the correct temperature to encourage the hatch. Look for the floating nymph drift along on the surface as it emerges and then suddenly flies off after it’s wings have dried. This is the danger time for the insect. If this event has caught the eye of a trout it will rise and slurp it greedily down in an instant. Try an emerging nymph pattern, suspender buzzer, or dry fly that matches the hatching insect in color.

If the trout are ignoring the action on the surface they may be taking the mature rising nymphs just before they hatch. This is a very common situation in the early days of the first hatchings. It is as if the size of the newly hatched insects intimidate the trout. It can take a couple of days before they start feasting on them so it is a good idea to concentrate on the rising nymph imitation rather than the emerging mayfly dun. These fish are not preoccupied with one specific insect so try a gold bead head gold ribbed hare’s ear nymph. Fish it slowly on a floating line near the area of the hatchings. The trout will see the gentle rising action on the retrieve as a nymph floating to the surface to hatch. With patience it should get a strike. Alternatively try a normal gold ribbed hares ear cast at 45% upstream and left float with the stream without any retrieve until it has swung right past your position. Hopefully this should look to a hungry trout like an insect floating on the surface just about to hatch 

Why do we call mayflies, mayflies? In my experience it is June that is the best month for these insects. June flies does sound quite correct does it? (Australian, New Zealand and South American Fly fishers would call them November flies or December flies and that sounds even stranger!) In your rush to get involved early in the annual sport of Mayfly fly fishing, first stop and use your eyes. Are the trout taking the new hatching duns or are they slurping the smaller black gnats, caenis or other local insects that tend to swarm at this time of the year. Tie on the Black Gnat fly or similar imitation to match local conditions. There will be many days later in the month where a mayfly imitation would be more successful. Then again use your eyes before casting. Look in the water for the amount of discarded shucks, the old nymph skin, floating in the water. Look under the leaves of the bushes on the side of the river bank and hunt for the adult mayflies. Then select your fly that best matches them.

Here is an extract from a fishing Diary :-

"Trout can be strange. I experienced my first Green Drake mayfly hatch on the evening of the 20^th May...they are huge flies! They were everywhere, I was grabbing them with my hands and taking a good close look at them. There were also several other flies hatching too.  The funny thing is that the fish never fed on them on the surface.  I fished from 6pm till dark and only saw two rises all evening.  I tried a few different drys and a few nymphs with no luck. Finally caught a small brown on a black woolly bugger with a bit of flash in it’s tail. We had had a good bit of rain the last couple of days and I think that was why the fish were kind of screwed-up.

The next day every fish I showed a dun mayfly to went on the attack. The cloud cover gave me a 6 hour hatch, with the duns coming off the water all afternoon long. I never did see a spinner fall, evening weather was a little strange. On the third day of my long weekend fishing trip the fish were nailing emegers during the heavier rain, and dries during the calms. I got soaked, but got some beautiful trout in between soakings."

OTHER TROUT FOOD
Other groups of insects go through a similar sort of development and form part of the trout's diet. Midges develop from bloodworm lava stages to pupa and then adult. Caddis and sedge flies lava is encased for protection before it develops into it's pupa stage and then into the adult. Stonefly and damsel flies nymphs are a main trout food item rather than the adult fly stage. Other non aquatic flies like the hawthorn and crane flies (daddy long legs) are also taken when they flutter over or on the top of the trout's home. Terrestrials like ants and grass hoppers are also gobbled up if they fall into the Water.