My theory, stated briefly and more explicitly, I hope, than was the case in my article in The Field, is that under circumstances in which the wet-fly behaves more as does some creature having the power of swimming through the water, it is better to imitate this creature than any natural fly on the water, which cannot in any case behave in such a manner; and what I wish to advocate is, that imitations of these aquatic creatures should be made and used.
CHAPTER II
Corixæ[3]
[3] Rewritten from an article in The Field under the heading of “A New Trout Fly.”
While fishing in a water where the trout are very numerous in the spring of 1897, I found that I could hardly catch a single trout in the day with the fly. The weather was cold and windy, and showed no signs of mending. At last, one day, I opened a trout, one of the few that I had caught during my visit, and found the stomach full of some insects belonging to the family of Corixæ. These insects are very commonly called Water Beetles, or Water Boatmen. They, however, are not beetles but bugs (Heteroptera), and are not the same as the true water-boatmen, the Notonecta glauca, though they somewhat resemble it in appearance.
On finding these insects in the trout I took some of them home, and made imitations of them. With these the next day I caught a number of trout, though the weather was just as unfavourable. Since then I have improved somewhat upon the imitations I then used, and in waters which are inhabited by Corixæ. These imitations have met, both in my hands and in the hands of others, with greater success than any other form of wet fly.
It is an extraordinary thing, considering the number of men who have written on trout fishing, that it has apparently never occurred to one of them to describe an imitation of one of this large family of insects. Mr. Halford, in his Dry-fly Entomology, indeed states that he has frequently found them in the stomachs of trout, but he does not even suggest that an imitation of them might be made.
There are many species of Corixæ which inhabit our waters, but the commoner sorts are so similar in appearance that many of the species are very difficult to distinguish even by an expert, and but little work has been done with regard to them. Therefore I have come to the conclusion that a similar dressing on different sized hooks will be quite sufficient to deceive the unscientific eye of the trout. This conclusion is corroborated by the fact that I have several times had an imitation Corixa seized by a trout when it was sinking, and before I began to draw it through the water, which is, I take it, a fairly severe test as to the accuracy of the imitation. Colonel Walker and Mr. Herbert Ash have also had the same thing happen to them when fishing with my imitation Corixæ.
Corixæ vary much in size, the largest and one of the commonest species being the Corixa geoffroyi, which is about half an inch long. In all Corixæ, the head is wide and is attached but slightly to the body. It is convex in front and concave behind, so as to fit the end of the thorax, and is as wide as the wings when folded and at rest. These insects possess four wings, which they frequently use, though they are somewhat clumsy in starting from the surface of the water. I have sometimes, however, seen them fly considerable distances. The anterior wings resemble the wing-cases of a beetle; they are hard and shiny, brown in colour, with dark mottled markings upon them. The posterior pair are transparent. The abdomen is light yellow and fringed with hairs, and there are transverse lines on the dorsal surface of the thorax. As, however, these markings on the thorax and wings are hardly visible to the naked eye, they give the Corixa a generally brownish and shiny appearance. Of the legs, six in number, the hind pair are most used in swimming. They are somewhat flattened at their extremities to a paddle shape, and are fringed with hairs. I have seen the hind legs of the Corixæ when the insects have been suspended motionless in mid-water, standing out at right angles on each side of the body; and as in the imitation I am about to describe, the legs take this position when the fly is at rest or sinking in the water; this explains the fact of the trout taking them in the way I have mentioned above.