Nat] AND SYMBOLS. 245 



Some of Nature's Police. 



So numerous are the "green-oak moths" that their pro- 

 geny would shortly devastate a forest were they not subject to 

 the attacks of another insect. This insect is a little fly, of a 

 shape something resembling that of a large gnat, and which has, 

 as far as we know, no English name. Its scientific title is Empis. 

 There are several species of this useful fly, one attaining some 

 size ; but the one that claims our notice just at present is the 

 little empis, scientifically Empis tessellata. He is a terrible 

 fellow this empis, quiet and insignificant in aspect, with a sober 

 brown coat, thin and genteel legs, and just a modest little tuft 

 on the top of his head. But sad is it for the gay and very 

 green insect that flies within reach of this very estimable indi- 

 vidual ! The great hornet that comes rushing by is not half so 

 dangerous for all his sharp teeth and his terrible sting. The 

 stag-beetle may frighten our green young friend out of his 

 senses by his truculent aspect and gigantic stature. But better 

 a thousand stag-beetles than one little empis. For when once 

 the thin and genteel legs have come on the track of the little 

 moth, it is all over with him. Claw after claw is hooked on 

 him, gradually and surely the clasp tightens, and when once he 

 is hopelessly captured, out comes a horrid long bill and drains 

 him dry. c. o. 



Natural Selection. 



Natural selection, or the survival of the fittest, does not 

 necessarily include progressive development ; it only takes ad- 

 vantage of such variations as arise and are beneficial to each 

 creature under its complex relations of life. And it may be 

 asked, What advantage, so far as we can see, would it be to an 

 infusorian animalcule, to an intestinal worm, or even to an 

 earth worm, to be highly organised 1 If it were no advantage, 

 these forms would be left by natural selection unimproved or 

 but little improved, and might remain for indefinite ages ia 

 their present little advanced condition. o. 



