Diptera and Perlidæ.
In imitations of Diptera and Perlidæ the body and hackle are put on in the same way, except that the hackle should be allowed to project sideways as well as downwards; for as the wings are horizontal in these flies, the fibres which project sideways will not interfere with the position of the wings, as they would do in the Alder and Caddis flies. The body and hackle, when put on, should therefore appear as shown in [Fig. 14].
Fig. 16.
The wings of these flies are perhaps the most difficult of any to put on. To put on wings which diverge from each other as in the Blue-bottle, two portions of the quill feathers from opposite sides, prepared as described for the Alder and Caddis flies, should be laid upon each other, as shown in [Fig. 16]. The hook should then be taken in the left hand, and held by the bend between the first and second fingers, with the head pointing towards the right. The wings are then laid flat on the body with the right hand, and held there firmly with the left thumb. The wings are now tied in, the quill and part of the fibres attached cut off close, and the head finished off. The illustration of the imitation Blue-bottle, etc., shows its appearance when finished.
Those Diptera whose wings lie, when at rest, one over the other (as in the case of the Cow-dung), my reader will see that I have represented in my imitations, with their wings spread to a certain extent. This is because I have seen that, in the natural fly, when it falls on the water, the wings are most often in this position.
In Perlidæ, whose wings lie one over the other, the wings should be put in the position they occupy in the natural fly, instead of across each other, and the fly will appear when finished like the illustration of the imitation Yellow-Sally.
The dressings which I have found most successful will be described with each fly. It will be noticed that I have put tinsel on many of the flies which have been dressed hitherto without. My reason for using it so freely is because this is the only way to produce a peculiar effect which is seen in certain flies when viewed from under the surface of the water; and as this is how they must appear to the trout, it is best to imitate this effect as nearly as possible.
The bodies of many flies are covered with short hairs. When these flies fall on the water, an air bubble adheres to these hairs, and, seen from below the surface, produce a brilliant metallic effect, with the colour of the body showing through in places. Ribbing the body of the imitation with tinsel reproduces this effect accurately.