A little entomology

The modern angler expends much time in the study of his beloved pastime; he realises that there are joys in fishing beyond the mere capture of fish, and the results of the interest he displays in everything in the slightest degree connected with the sport are evident all around.

Very few are now content with what used to satisfy thoroughly their forefathers. Consider the vast improvement that has been made in rods; the dainty weapon of the present day is but a toy in comparison with the long, heavy, unwieldy rod of our ancestors, and it is capable of giving more efficient service and in addition infinitely greater pleasure than its cumbrous predecessor. Reels and lines have been improved almost out of recognition, while there has been a refinement in casts and flies and tackle generally which is obvious to anyone having a few years experience of angling. These changes have been partly necessitated by the advancing education of trout, a consequence of the ever-increasing popularity of angling as a sport; but they are also largely due to the angler's demands for comfort and enjoyment. He objects to use implements which call For an excessive expenditure of energy; but what principally receives his disapproval is the fact that even a heavy trout hooked on coarse tackle makes but a feeble resistance; he desires no humiliating triumphs.

The great majority of fishermen now concern themselves with matters to which their forefathers gave only the slightest attention, e.g., with the artificial rearing of trout, stocking of waters, pro vision of new forms of food and care for existing supplies, prevention of pollution, destruction of unwelcome aliens that prey upon the more desirable trout, or consume the food intended for them, suppression of predatory birds. By a judicious arrangement of stones and boulders they form new streams and pools and so convert barren stretches of a river into fine trouting water; they acquire new reservoirs, stock them, and thus add very considerably to the sport-giving capacity of the country. They rear aquatic flies of various kinds and transport them to new waters or to such as are deficient in certain species. There is no limit to their activities.

It is very difficult at the present time to find an angler who is not intensely interested in the life-histories of the flies on which trout feed and of which he is accustomed to make copies wherewith he seeks to deceive the object of his search. The entomology of the. river and loch has the power to interest anyone, be he angler or not, for a more fascinating study does not exist.

For the angler it possesses additional attractiveness in that, no matter how great his dexterity and manipulative skill may be, his success must to a high degree depend on his intimacy with the flies of the water-side.

Many are deterred from the study by the. forbid ding nomenclature, but the scientific names are really necessary to avoid confusion - the same popular name is applied to different insects in different localities, e.g., the term May-fly is given to the Green Drake, the Stone-fly, and the Grannom, all flies that differ from one another as much as they possibly can. However, as we shall take other means to prevent confusion, we intend to use in our discussion the scientific appellations only for the different orders.

All flies, which go to sustain trout and which therefore concern the angler, may be roughly divided into the following orders: -

Order	Ephemeridae	Trichopteria	Perlidae	Diptera
Wings	Upright	Pent-shaped	Long, flat, parallel	Short, flat, diverging
Representatives found in most Scottish waters	Duns and Spinners (Olive, March Brown, Iron Blue)	Caddis-flies (Cinnamon Sedge)	Stone-flies (Needles)	Gnats and Midges (Blank Gnat, Gravel-bed)
Artificials	Olives of various shades. March Brown, Red Quill Iron Blue, Blue Hen Black Spider	Corncrake Black Sedge. Grannom. -	Needle-brown - - -	Badger Spider Black Midge Gravel-bed -

It is impossible and certainly unnecessary to examine in complete detail all these flies; in fact they have not all been thoroughly investigated; but we shall give a brief life-history of each order that is typical of that order.

The Ephemeridae enjoy a varied life, the greater part of which is spent beneath the waters. The duration of the winged state is infinitesimal as compared, with that of their aquatic existence. The egg soon hatches into a larva which, according to its species, may burrow in mud, crawl or creep among stones, swim from one shelter to another. All larvae alike prey upon minute organisms, until for each the appointed time arrives for its transformation. The period required for the full development of the larva varies, and it may be delayed by unto ward weather conditions or hastened by favourable circumstances; but, when it passes, the larva reaches the air, in some cases by ascending to the surface of the waters, in others by moving towards the bank.

Species which adopt the latter method afford the angler the best opportunities for observing the emergence of the "winged insect. By turning over a few stones close to the edge of the stream, he will soon be rewarded by finding on the underside of one of them a larva or nymph on the point of under going its metamorphosis. He will know when to prosecute the search by noticing fully developed flies resting along the margin of the stream. The large Evening Olive, a conspicuous fly on the Tweed in July, is one species which is easy to observe, coming as it does to the gravelly shores for the pin-pose, and spending quite a long time in the process, of extricating itself from the nymphal envelope. Some, which rise direct to the surface, are apparently able to emerge without effort and almost instantaneously.

The newly fledged insect is known as a dun or sub imago. It is not yet fit for long flights, but is keen to test its wings. Those which do not require a grip of dry land before they can enter upon their aerial life, sail quietly down stream, their wings gently quivering the while, presumably preparing for the great adventure. The voyage is fraught with danger from the hungry mouths below; but always some escape all perils and rise into the air.

Naturally the duns are always borne down by the current. Why, therefore, does not the lowest pool of the river, the loch or the sea, in time receive all the flies and consequently also their myriads of eggs? We have often thought of this problem and frequently have determined to note the progress of the flies down the stream and the subsequent behaviour of those that survived the dangers; but the sound or glimpse of the rising trout has invariably succeeded in diverting our attention from the flies to the spreading rings. The flies must, when they do take wing, head upstream, or our rivers would be without a single representative of the Ephemeridae.

The dun has not yet attained to completion. It has still to suffer or enjoy another transformation. Alighting on some convenient spot, the insect withdraws from its already beautiful form an infinitely more delicate model of itself even to the filmy iridescent wings and tender seta;. It is then termed a spinner or imago, the perfected fly. The pale watery dims, which in their thousands throng our lochs and reservoirs on quiet, still evenings of summer, afford one the most frequent opportunities of observing this final emergence. They settle anywhere and everywhere, on stone and rock, weeds and gravel, and even on the angler's person.

The fragile spinners have hut one care and one occupation, the perpetuation of the species; they cannot feed, but spend all their time in airy dance and visits to the stream for the purpose of laying their eggs. When these duties are over, they fall exhausted, lifeless on the water, but the whole wonderful cycle has begun, and in due course the duns and spinners will greet us by the river.

To the Ti'ichoptera, the flies of the hairy wing, belong the sedge-flies and caddis-flies. They likewise spend a life of infinite variety and stirring change. They are found in every type of water, running and still, and no one can have failed to observe the fluttering clouds of flies so plentiful on summer days and evenings, or the curious abodes of the larva; or caddis-worms, as they are called. In one respect the larva; of the many species are alike in that they manufacture for themselves tubular homes which they decorate on the outside in fashions distinguishing the various species with sand, gravel, shells, or straws, and so cunningly are these tubes constructed that by reason of an ingenious admixture of materials their density is only slightly greater than that of water. The larva protrudes its head and its six feet and moves freely about from place to place, dragging behind it what is to all appearance a huge burden.

In time the larva pupates or enters into a period of rest preparatory to changing into the winged state. During this time it does not feed or move about, but, being still alive and wishing to remain so, it must breathe and also protect itself from its enemies. It effects this double purpose by closing up the entrance to its home by means of a sieve or grating through which water carrying the requisite oxygen can freely pass, but by which irritating foreign matter and predaceous creatures are excluded. After awaking from its sleep the larva, by its own characteristic method, sets out for the air; there it undergoes the great change and emerges fully fledged. There is no intermediate stage corresponding to the sub-imago of the Ephemerida.

Though many caddis-flies rejoice in the gloaming, and some are even more nocturnal in their habits, others again select the full light of day for their aerial adventures. They are none too strong upon the wing; some flutter bravely enough, while their relatives seem to find all necessary pleasure in crawling over or remaining quiescent on old wood beside the water. They are never far from the edge of stream or loch, and all lay their eggs on the water, therefore trout know them well.

It is quite possible that some species of sedges have a flavour that is not to the trout's liking. There is a sedge-fly commonly seen floating en Loch Leven; the boatmen call them "hornies," probably from the long antenna which distinguish the order Trichoptera, and some at least declare that trout absolutely ignore them. Whether it is true or not we cannot say, but we have certainly never seen trout taking them. In this there is an assumption that trout have a, memory for flavour; but no one who has seen the avidity with which they rise to the Iron Blue duns, and the accuracy with which they single the little morsels out from amid other flies, as well as the suddenness of the fate of the first arrival of a hatch, can doubt that the supposition is justified.

Many anglers will associate the sedge-flies with the few hours of semi-darkness in June and July, and will no doubt recall happy rimes spent on smooth-flowing shallows, when the trout quietly stopped the progress of the slowly-moving flies and valiantly fought to regain their liberty. The dry- fly fisher has these memories; but he will content himself with them and not seek to renew them, for lie has all the sport he requires in the full light of day or the grey of gloaming, when he can follow the fate of his fly and answer every wile of his plunging captive.

Members of the Trichoptera are readily recognised by the long pent-shaped wings drooping over the body.

The Perlidae or stone-flies are relatively of small importance to the dry-fly man. They inhabit quick-flowing strong streams, not one species, so far as we have ob served, selecting still water for its habitation. By far the best known is Perla maxima, a deadly bait on the great majority of Scottish rivers. It is interesting because it is a denizen of the water and forms a valuable food which rapidly brings trout to the summit of their excellence, making them all the more desirable to take later in the year by means of a small floating fly.

The larva is known as the creeper, also a favourite bait for trout and grayling, and a terrifying creature to handle for the first time. It prefers steep gravelly shallows and broken water generally, which it leaves at the call of the air for the stony bank. There it enters the winged state, but it hides and scuttles among the stones, either unwilling or unable to indulge in flight. The flies venture forth more freely at night, when they may be collected easily by means of a lantern. We have that only on the evidence of other anglers, for we have never considered them worth the trouble. Of course, we have proved the deadliness of the Stone-fly; but even in the height of its season we prefer to use, and find it good to use, a small floating copy of dun, sedge, or midge.

The smaller members of the order are known to anglers as Needles, and their development, we expect, for we have not studied them as we hope yet to do, is similar to that of the most important species. All are recognisable at once by the long, flat, parallel wings extending down the body. Yellow Sally and Needle Brown are two of the commonest lesser stone-flies, and in certain districts are abundant enough to merit some attention from the angler.

Diptera, i.e. two-winged flies, are an innumerable class. Those which have an aquatic origin or live in close proximity to the water, are full of interest, including, as they do, gnats, midges, smuts; the gravel-bed, a crane-fly, belongs also to this order. These undergo a complete metamorphosis, that is, they are found in larval, pupal, and winged states.

The gnat (culex) delights in stagnant backwaters of the river, in which the larvae display their wonderfull ways and from which on assuming wings they reach the haunts of the trout. The larva hangs vertically in the water with its tail end at the surface absorbing oxygen, while its head swings about below in the eternal hunt for food. On being disturbed it sinks into safety, but recovering courage or being forced to come up for air it: gains the surface again.