"Fly fishing," remarked the crusty Dr Samuel Johnson, "may well be a very pleasant amusement; but angling or float fishing I can only compare to a stick and a string, with a worm at one end and a fool at the other." Be that as it may be, an event occurs each spring that is eagerly awaited by fly-fishermen everywhere. The "rise" of the mayfly often occurs, as the name implies, in May, and provides an annual "happy hour" for anglers. The fish jump eagerly from the rivers and lakes in their eagerness to catch the prolific insects, and their undiscerning enthusiasm makes the period a very fruitful time for fishing.
The mayfly nymph spends a year or two buried in the mud or sand at the bottom of a stream or pond. From there it emerges into the open air, with millions of its fellows, in this annual event we call the "rise". It then undergoes a series of metamorphoses to become the adult mayfly - a large insect, two inches long or thereabouts, with semi-transparent lemon-coloured wings.
Adult mayflies have a brief but pleasurable existence: their entire energies are exclusively devoted to mating on the wing. This they do in dense and feverish swarms, the objective in the case of any individual often being achieved within an hour or two. But this mayfly heaven proves to be ephemeral; the flies, far from being immortal, have a lifespan of only a few days. Almost immediately the female deposits eggs into the river or pond, she and her quondam paramour collapse exhausted on the surface of the water - there, with wings outstretched, to expire in a classic denouement worthy of Fonteyn.
It is known that mild, dry, sunny weather causes this brief sojourn en masse above the water of the flying insects to take place a little earlier than usual. But the reason why has proved to be elusive. It may be because the water temperature is high. Alternatively, it may depend on the amount of sunshine, which heats the silt of the shallow waters where the larvae grow. Or the sunshine may help the growth of algae which provide the food, and bring about an early hatch. Or then again it may be rain-related, since low rainfall means lower water levels, leaving the water rich in nourishment.
Whatever the reason, the annual "rise" of the mayfly provides a tasty morsel for many a waiting trout. Their abundance makes the fish more greedy and less canny than they normally are, and the "rise" a bonanza time for the angler casting from the bank.