WATER-FLIES.
[To THE EDITOR OF TUC "SPECTATOR."] Sin,—In the Spectator of September 7th a reviewer says that there are some absurd theories in " How to Fish," a hook written by me. " We need but mention," be remarks, " his proposal to compile a calendar showing what flies would be on the water, not only for each week, but for each separate day, of the season. The experienced advice of Mr. Marston and Mr. Hardy seems to have dissuaded him from attempting this." That is to say, my theory as to the natural history of water-flies is the absurdest thing in an absurd book. As this is not good to hear from the Spectator, which takes a scientific interest in natural history, I would fain make a few remarks. I would appeal from the reviewer to yourself; and you, as judge of appeal, shall have the assistance of what we may call entomological assessors, correspondents who have thought about the question. Here is the issue. Practi- cally all trout-fishers take it for granted that when a particular fly which is due upon the water is not there its coming-out has. been delayed by cold, and that its birth will be brought about by warmth ; they understand that the immature insect can at will, or does by nature, remain immature until genial temperature comes. My own thought is that this must be a misapprehension. It seems to ine that a water-ft; mast come out into the air at a definite date after the laying if the egg from which it sprang; or be dead at that date ; or at that date be straggling into impaired comple- tion, alive, but not strong enough to reach the air. If this theory is absurd, it is absurd to believe that Nature is in- exorable in certain of her processes ; absurd, that is to say, to believe that we can have exact science. As adopting this con- clusion would range the Spectator with the men of knowledge against whom the Bishop of Rome is wrathful, I state my appeal to you and 'the assessors with some 'confidence. • You will, of course, understand that I am not inviting any " Down-with- the-Pope" entomology. What I should like to see is a state- ment of facts or of well-considered reasonings. This is a very interesting question, not a matter for judgment from casual impressions. Mr. Hardy, I may mention, did not dissuade me from the thought of endeavouring to compile the calendar. On the contrary, in a letter published in "How to Fish " he begins: "I agree with all you say as to periods and times of ' hatching ' "; only he mentions the fact that duns which do come out in due season "are brighter in colour when the weather is cold." I take hint to imply that if flies due on a particular day do not come out at all on that day, they are dead or numbed, and that perpetuation of the species is left to those the parents of which laid eggs later.—I am, Sir, &c., W. EARL HODGSON. Oakbank, Aberfeldy, Perthshire.
[The impracticability of Mr. Hodgson's proposal lies in his apparently supposing that scientific data exist for compiling such a calendar of insects for each day of the season. He might as well attempt to draw up a calendar predicting what the weather will be on every trout stream in every county on every day in any future year.—En. Spectator.]
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