Page:Popular Science Monthly Volume 70.djvu/61

Rh or half wings, are counted, the round sum of 360,000 species of insects now known is reached.

Estimates have been given showing that not more than one sixth of all forms actually existing have as yet been described and named, so that the number of species (not individuals) now living in the present period of the earth's history may be placed at about 2,000,000.

It is quite conceivable that man in his effort to understand nature everywhere surrounding him should not be satisfied merely to study all these existing insects and arrange them in a system of orders, families, genera, etc., but he would also wish to know how this greatest division of the animal kingdom, in specific numbers about doubly exceeding all other groups, has been developed, and how and when it has attained its present size.

If we would really learn the primitive history of the insect tribe, and not construct it in a speculative manner, we must descend into the depths of the earth in order to see whether or not a fortunate chance has possibly preserved some remains which might afford us an insight into the insect life of previous ages.

If, as mentioned above, the number of various species of insects now existing be taken in round numbers at 2,000,000, and for each species at least 1,000,000,000 individuals yearly, which, judging from the swarms of bees and gnats, colonies of ants and termites, parasites of plants (often millions living on a single tree), certainly seems legitimate, an annual total of 2,000,000,000,000,000 (two thousand trillions) individuals is obtained, while during the time that man has inhabited the earth some hundreds of trillions must have existed.

And of all these trillions of insect remains, which moderately computed (about 100 to a gram) represent 1,000 billion kilograms in weight, we have as yet found but a few hundred examples, and these have been accidentally enclosed in gum (copal), in peat-beds, or finally buried in hardened mud. They have thus become more or less well preserved, and again by chance have fallen into our hands. All these forms clearly demonstrate that the species of insects have not materially altered during man's sojourn on the earth.

It may now be concluded that these results must lead only to discouragement, for they show very plainly how small a percentage of the insect world escapes complete destruction, and how slight is the prospect of securing any of these remains.

Notwithstanding this, it has already come to pass that quite a number of fossil insects have been brought to light from analogous deposits of older periods, and the explanation may be partly found in the fact that even these older strata are to be estimated not only by thousands, but probably by millions of years, so that the sum total of vanished and preserved forms must evidently increase accordingly.