This experience of his exactly coincides with my own, though the six consecutive autopsies described above without my other similar experiences is a fairly strong piece of evidence. I am therefore inclined to believe that there is some good to be gained in following the sapient advice, verbal and written, to cultivate vegetation overhanging the river, beyond its advantage as giving shelter to the fish.
I will narrate the circumstances which first led me to use the caterpillar as a dry fly, as they may, I think, interest my reader.
I was lying on the bank by a large pool on a stream, and saw a little green caterpillar hanging from the branch of an oak tree, apparently trying in vain to pull himself up the thread by which he had so foolishly lowered himself, till he was uncomfortably near the surface of the water. I watched him, lazily thinking in a dreamy manner how very unkind it was of the trout to keep on rising, and yet not look at my fly. They were evidently feeding on something, but what it was I could not make out. The little green caterpillar was getting gradually nearer to the water, and I was beginning to think that the poor little chap would meet with a watery grave, when just as he touched the water a trout came up and grabbed him.
Little green caterpillars were evidently what the trout were feeding upon, and that was the reason that I could not catch one with a fly. I watched the branches of the oak tree overhanging the water for some time, and saw several caterpillars fall in and meet with the same fate. The next thing I did was to catch a caterpillar, scrape the fly dressing off my hook, and put him on it instead. I caught several trout in this way, but found that it was almost impossible to cast any distance without shaking off the caterpillar. After much trouble caused by this difficulty, which was very trying to the temper, as the caterpillars always seemed to come off the hook at the most critical moment, and having got a fairly good basket, I found it was time to return. That night I managed to make some fairly good imitations of the little green caterpillar to use on the morrow, instead of the natural ones. These imitations met with success, and since that time I have been able to improve on the dressings then used.
I have found many different kinds of caterpillars in the stomachs of trout, but small green ones of various sorts were decidedly the most numerous. The species I have most frequently found is, I believe, the larval form of the Tortrix viridana. I have never found a large caterpillar in a trout, though I have caught trout with imitations of them used as dry flies. I give the exact dressing of the green caterpillar; but the other dressings must be left to the discretion of the fisherman for alterations, as there are so many sorts of small caterpillars, some of them being extremely rare in one place and common in another.
Should the fisherman wish to see the sort of caterpillar commonest where he is fishing, he must seek them himself. Those only are useful which are on the trees overhanging the water. If there are oak trees the caterpillars will probably be green, and many kinds of caterpillars will be found which have rolled themselves up in the leaves of the tree upon which they live. I have no doubt that this imitation caterpillar will be looked upon as a poaching implement, but it is or should be used as a dry fly, and to use it successfully requires as much skill and power of observation as does the use of any imitation of a fly used in a similar manner.
How to make an Artificial Caterpillar.—A small piece of cork 1/32 of an inch thick, or less, and nearly twice the length of the hook, must be cut into the shape shown in [Fig. 17]. Next take a piece of quill rather longer than, and about the thickness of a large pin, from a tail or wing feather of a starling. This quill makes the foundation of the body. Split the thick end of the quill far enough to embrace two-thirds of the shank of the hook, and then tie it on the hook as shown in [Fig. 18]. Now fold the piece of cork, with the broad end towards the eye of the hook, over the shank of the hook and the quill, tying it in as shown in [Fig. 19].
Fig. 18. (left), Fig. 17. (center), Fig. 19. (right)