The Earth as Modified by Human Action eBook

DESTRUCTION OF INSECTS.

It is well known to naturalists, but less familiarly to common observers, that the aquatic larvae of some insects which in other stages of their existence inhabit the land, constitute, at certain seasons, a large part of the food of fresh-water fish, while other larvae, in their turn, prey upon the spawn and even the young of their persecutors. [Footnote:  I have seen the larva of the dragon-fly in an aquarium bite off the head of a young fish as long as itself.] The larvae of the mosquito and the gnat are the favorite food of the trout in the wooded regions where those insects abound. [Footnote:  Insects and fish—­which prey upon and feed each other—­are the only forms of animal life that are numerous in the native woods, and their range is, of course, limited by the extent of the waters.  The great abundance of the trout, and of other more or less allied genera in the lakes of Lapland, seems to be due to the supply of food provided for them by the swarms of insects which in the larva state inhabit the waters, or, in other stages of their life, are accidentally swept into them.  All travellers in the north of Europe speak of the gnat and the mosquito as very serious drawbacks upon the enjoyments of the summer tourist, who visits the head of the Gulf of Bothnia to see the midnight sun, and the brothers Laestadius regard them as one of the great plagues of sub-arctic life.  “The persecutions of these insects,” says Lars Levi Laestadius [Culex pipiens, Culex reptans, and Culex pulicaris], “leave not a moment’s peace, by day or night, to any living creature.  Not only man, but cattle, and even birds and wild beasts, suffer intolerably from their bite.”  He adds in a note, “I will not affirm that they have ever devoured a living man, but many young cattle, such as lambs and calves, have been worried out of their lives by them.  All the people of Lapland declare that young birds are killed by them, and this is not improbable, for birds are scarce after seasons when the midge, the gnlat, and the mosquito are numerous.”—­Om Uppodlingar i Lappmarken, p. 50.

Petrus Laestadius makes similar statements in his Journal for forsta urst, p. 283.]

Earlier in the year the trout feeds on the larvae of the May fly, which is itself very destructive to the spawn of the salmon, and hence, by a sort of house-that-Jack-built, the destruction of the mosquito, that feeds the trout that preys on the May fly that destroys the eggs that hatch the salmon that pampers the epicure, may occasion a scarcity of this latter fish in waters where he would otherwise be abundant.  Thus all nature is linked together by invisible bonds, and every organic creature, however low, however feeble, however dependent, is necessary to the well-being of some other among the myriad forms of life with which the Creator has peopled the earth.