Читать книгу Odd Showers, An Explanation of the Rain - Sir George Duncan Gibb - Страница 4

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In our temperate climate insects have not been known in recent times to exist in such abundance as to constitute showers. An exception, perhaps, might be made in favour of Ephemerae, which have been seen to fill the air for miles on the banks of the streams in the Midland Counties, dropping towards the surface of the ground or water, like fine drops of rain; or as Reaumur has described it from observation on the banks of the Marne and Seine, "When the snow falls with the largest flakes and with the least interval between them, the air is not so filled as it was around me with ephemerae: scarcely had I remained in one place a few minutes when the step on which I stood was quite concealed with a layer of them, from 2 to 4 inches in depth." The water near was thickly covered with them, and as they fell obliquely, the eyes, mouth, and nostrils were filled. These insect showers are welcomed by fishermen as the forerunners of abundance.

I have seen the same thing occur in Canada in the months of May and June, generally May, along the banks of the St. Lawrence, where the Shad-fly (an ephemeral insect) comes as an annual visitor in countless swarms in most of the villages and towns on each side of that noble river as far up as Montreal, during the time that the shad-fish is tracing its course upwards to deposit its spawn. The fish at this period is caught in large numbers; the shad-fly forms the principal food of the fish, and on its first appearance the markets are generally well supplied with the latter. The quantity of these flies in the air resembles a heavy fall of snow, and everything is filled by them. On the banks of the St. Lawrence as far as the eye can reach, the air is filled with falling flies, as if they came from the clouds. Fortunately they are harmless, and do not last longer than from two to three days in any one locality. The question is asked, Where do they come from? They are hatched simultaneously in millions from the pupa and aquatic larvae of the parent insects in all the streams and rivers, for probably an extent of many hundred miles on the banks of the St. Lawrence.

Showers of Phryganeae (Caddice-flies) occur in some parts of the continent of Europe, not unlike those of the ephemerae, when the air is said to be filled for a considerable distance. As travellers well know to their misfortune, Mosquitoes exist in some countries in numbers that baffle description, and their blood-thirsty habits induce them to attack one in countless myriads. They rain perhaps in equal, but not greater number than the ephemerae and their allies. The Gnats are just as bad. The larvae of these insects are aquatic, and abound in stagnant water, but it is doubtful whether they ever exist in such numbers as the ephemerae, although perfect pests to human kind.

In insect showers all must yield precedence to the Locusts. Clouds of these, according to the accounts of various travellers, are often so dense and extensive as to obscure the sun in such countries as the East, various parts of Africa, Tartary, Russia, and Poland. Their occurrence is easily explained: swarms of these insects appear in a certain locality, deposit their eggs, which soon come to maturity, and the larvae march onwards, eat up and devastate everything before them. In three or four weeks they are metamorphosed into the perfect insect, and mount in millions. Africa has been ravaged by them from time immemorial, and Holy Writ bears evidence of the miseries they have produced. In 1797 Barrow observed them in South Africa in swarms, covering the country for an extent of 2000 miles. Vast clouds frequently appear in Tartary, and extend westward into Poland and Russia.

Clouds of Ants are sometimes seen in Europe in August or September, just emerged from the pupa state. They have been compared to columns of vapour as they rise in the air or change their position, twisting and whirling about in various directions.

Of living showers, insects are unquestionably the most abundant, from the reasons which have been given; it is not so with other things. If fish or other bodies rain, it is from some unusual and peculiar circumstance, as shall now be shown.