Half hours with insects . cal^^^* burrows firmly cemented and varnished so as to bewater proof. It should be here men-tioned that certain broodsT «• r^ » A- r^ /i of this species appear once Larva of Seventten 1 ear Cicada. ^ ? in thirteen years, and thisindicates that the ancestors of the present species wentthrough their round of existence in two years, as in theother species. How the wonderful divergence in habits wasbrought about would form an exceedingly interesting subjectof inquiry. We are indebted to Dr. W. I. Burnett for an interestingsuggestion concerning the chances of life in this
Half hours with insects . cal^^^* burrows firmly cemented and varnished so as to bewater proof. It should be here men-tioned that certain broodsT «• r^ » A- r^ /i of this species appear once Larva of Seventten 1 ear Cicada. ^ ? in thirteen years, and thisindicates that the ancestors of the present species wentthrough their round of existence in two years, as in theother species. How the wonderful divergence in habits wasbrought about would form an exceedingly interesting subjectof inquiry. We are indebted to Dr. W. I. Burnett for an interestingsuggestion concerning the chances of life in this insect, andthis may give us some hints regarding the enormous waste,so to speak, of life (though after all it is an example of theeconomy of nature) involved in the struggle for existenceamong animals. Says our author, in a paper read at a meet-ing of the American Association for the Advancement ofScience (Albany, 1851), The female has about five hundredeggs, which, from certain relations of the other sex, which I 2. PACKAKDl INSECTS OF THE GARDEN. 35 have made out microscopically, are probably all or nearly allfecundated. We have, then, for every two individuals whichhave appeared this year, a deposit of five hundred embryosfor the generation to appear seventeen j-cars hence. Now, from what has just been stated about the uniformityof their numbers, each time, it apixars that from the liabili-ties of destruction during the long term of seventeen years,out of these five hundred embryos, only two appear certainof life and appearance iu their perfect state, that is, just re-placing the two parents. The chances of life therefore withthis iusect, are, in round numbers, two in five hundred. Thiscalculation may seem strange to some, but if we reflect, itcan scarcely be otherwise ; for suppose the chances weredouble, that is, four in five hundred, then we should have ateach time just double the numbers of their last time, whichobservation has shown to be untrue and which would augu
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectinsects, bookyear1881
