This is not a guide to entomology. I have included books in the appendices to lead you into this topic, but no fly fishers guide would be complete without at least a passing reference to the stuff we are trying to copy. Let me give you the main food items on the trout menu and describe how the trout take them. I begin with the aquatic food forms in order of significance;
Buzzer, midge, or chironomid - depending on how pretentious you want to get.
These insects (non-biting, you only find those in stagnant water) are the bread and butter of the stillwater trout's diet. They are supposedly called buzzers due to the noise their wings make. It's only in the UK that we anglers call them buzzers - I reckon it's because we have more imagination than everyone else. Chironomids is the Latin name, it might seem archaic, but if you know Latin names them you can speak to anglers of all countries without the confusion of having to describe the damn thing. A very useful thing when travelling with the flyrod.
The life cycle of the buzzer is egg, larva, pupa, adult, egg and so forth.
If you carry a good selection of buzzer pupae, and emerges, in various colours and sizes then you can virtually guarantee sport at any time of the year on any stillwater. Fish feeding on buzzer pupae just beneath the surface do so with the characteristic head and tail rise. Emergers are taken extremely gently (sipped).
Incidentally if you are close enough to a rise and you see an air bubble left on the surface then the fish has taken a fly from the surface. The air is sucked in with the fly and expelled through the gills, leaving that bubble as a sort of clue.
The red larva of the buzzer is the coarse angler's bloodworm.
Sedge, caddis or trichoptera
Big moth-like creatures but with hairy wings as opposed to scaly. Their cycle is egg, larva (which often, but not always, build little homes of stones and rotten vegetation and carry them around - I jest not), pupa, adult.
Trout feed on the larvae (cased caddis) frequently during the early part of the season when dwelling near the lake bottom.
The pupae are generally fed on just prior to hatching. The rise form is usually a whorl; a great swirl.
The adults are generally slashed at by the fish, since they are likely to fly quickly away and the trout know this. Egg laying sedges often do so by flurrying across the surface leaving a little V-wake behind them. (Remember muddlers?)
In this movie I have captured a quite staggering amount of adult sedges...
What we pick next depends on the water, but perhaps:
Upwing, dayfly, mayfly, ephemeroptera
This large order of insects consists of relatively few insects of use to the stillwater angler. There are mayflies, lake olives and caenis. Their life cycle is egg, nymph, sub-adult fly (sub-imago) the spinner.
Mayflies (Ephemera dancia and Ephemera vulgata) I have now, finally after only 20 years encountered. I had to travel to Corrib to meet them. And we caught fish on buzzers. Many anglers use the nymph of the mayfly for stillwater fishing. This however, at best is suggestive fishing, more often, lure fishing. There are no mayflies in most reservoirs and the fish know nothing of them. Also mayfly nymphs burrow in the mud until they are about to hatch, when they do so all at once. A lone mayfly nymph must come as a surprise; maybe this is the secret of success?
Lake Olives are another of those myths. I seem to recall fishing such a rise in the dim and distant past. I remember using dry Greenwell's and damp hares ears. They exist no more on the waters I fish in East Anglia. The nymphs are imitated using pheasant tails and hares ear nymphs.
Caenis (anglers curse - which is the rarely used angler's name for them) are however a reality. They are small (hook size #16-18) creamy-white flies. You know when they are hatching because you suddenly find yourself in a blizzard even though it is warm muggy evening. Then the flies decide to shed their outer skins (transforming into spinners) and do so all over you. They are in your hair, in your eves, up your nose. All great fun.
And the fish are all the while going berserk. Rising everywhere and being real bastards, just as I said they could be. They often cruise with their mouths open along the surface taking hundreds of flies at a time, well perhaps only dozens. But how the hell do you strike on an open mouth? The flies are engaging in a frenzied aerial orgy, the trout, in a mass insect slaughter and the angler is pulling his hair out in frustration. It is a wild and merry time. The Answer? Fish a black lure, but see May off the banks for the full story.
Damsel Fly, odonata
These large blue-green (male) and brown/tan (female) insects are rarely taken in adult form (although I have seen trout leaping clean out the water in New Zealand to take them on the wing) but nymph form makes a sucker out of the trout. Wiggly damsel nymphs are best.
Alder Fly, megaloptera
The Adults are rarely taken by the trout - some say that they do not appreciate their taste - but the larvae feature in their early season diet. The adults are similar in appearance to sedges, but without long antennae
I have encountered these hard winged flies in Scotland and overseas, but are not in existence in my part of Britain. They are an absolutely essential part of early season approach in areas where occur, especially the nymphs.
There are various other aquatic fauna, some you will need, some you might:
Lesser water boatman (corixa): trout feed on these in the shallows. A great summer pattern in and around weedbeds.
Shrimp, great diving beetle and hoglouse are all imitated by fly-fishers.
Daphnia (water flea): are very small creatures and can appear in the water in great number. The fish feed extremely well in them (large population explosions of these creatures must be, for the trout, something akin to swimming in lentil soup). Unfortunately daphnia are really too small to imitate. When the daphnia are near the surface (during cloudy days) then fish hot orange lures, when deep (bright conditions) fish lime green or black. Fish feeding on surface daphnia, usually do so moving very quickly, upwind, often with dorsal fins out of the water. The speed these fish can move, can be really quite surprising.
Migrating Snail: Becomes very important once or twice a year when it decides to float just beneath the surface and move to new grounds. The event is usually held sometime in late July and for the angler who is smart enough to realise what is happening and remembers to carry a few artificials, finds that good sport is there for the taking. Trout feeding on these floating snails appear to rise in a similar fashion to midge feeding. It often takes a little while to discover the truth.
Tadpoles and Frogs: both succeed in taking fish, with the former a large feature of trout's diet on some waters.
Fish: trout spend a great deal of time eating fry and small fish. The reservoir fisher, in order to catch imitatively, at certain times of the year must carry the appropriate artificials in various sizes. There are three important things with regards to fry feeders:
1. Often it is important to go just beneath shoals of fry and work your lure underneath them - this is why specialist fry-fly fishers carry heaps of sinking lines.
2. Fish can follow individual fry and chase them up to the surface; get your fly down to the trout's depth and pull it up, expect takes as you hang your fly just beneath the surface. This behaviour can be identified by the sudden appearance of little fish jumping clear of the surface with a large trout in hot pursuit.
3. Trout sometimes herd shoals of fry and feed on them by smashing into them and shocking the little ones so that they float stunned on the surface where they can be taken by the fish at leisure. Simply cast your floating artificial into the activity and wait. You will know at once what is going on by the fleeing of fry, leaping clear of the water in their haste to avoid the predator. Fry feeding is very easy to identify. When the fish returns to take the stunned he often does so incredibly gently.
Trout swallow fish, head first. It is said that brown trout hit large fry at the front third, rainbows a little further back at say halfway. Seagulls also feed on fry on the larger lakes; find the birds and you find the fish.