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POPULAR SCIENCE MONTHLY 



Lord Walsingham goes on to suggest that this intermittent dis- 

 play of bright coloring probably has as confusing an effect iipon 

 birds and other predaceous vertebrates as upon man; and that on 

 this hypothesis such colors can be more satisfactorily accounted for 

 than upon any other yet suggested. 



This explanation is easy to understand and gives renewed em- 

 phasis to the oft-repeated statement that nothing in Nature is with- 

 out significance. In the case of the Catocala moths one readily 

 perceives that when driven to flight by a woodpecker or other bark- 

 searching bird a moth which shows during a rapid irregular flight 

 bright colors, and then alights, hiding the colors and instantly assum- 

 ing entirely different hues, blending with the surroundings, would 

 stand a better chance of escaping from a pursuing bird than a moth 

 which had no bright colors with which to confuse the bird and pre- 

 vent its seeing the place where the insect alights. 



These insects are excellent illustrations of the combined action 

 of the various forces which Darwin classed together under the term 

 " natural selection." The factors involved are three — multiplica- 

 tion, variation, elimination. 

 In nearly all organisms more 

 young are produced than can 

 mature. In these young 

 there are infinite variations 

 all directions. Some of 



m 



these variations fit the in- 

 dividuals possessing them 

 better to the conditions of 

 life than variations in other 

 directions. Consequently, 

 the possessors of the latter 

 will be eliminated in the 

 struggle for existence and 

 the former will escape 

 Their young will in part at 

 and thus have an advantage 

 Thus there is an ever-increas- 



COHAL-WINliED LoOCST IN FlKHIT. 



elimination, and mature to reproduce 



least inherit the favorable variations, 



which will lead to their reproduction. 



ing tendency to a more perfect adaptation to Environment. 



On the rocky hills and sandy plains of New England there are 

 several species of grasshoppers or locusts that also illustrate these 

 principles. If you walk along a strip of sandy land in summer, you 

 start to flight certain locusts which soon alight, and when searched 

 for will be found closely to assimilate in color the sand upon which 

 they rest. On a neighboring granite-ribbed hill you will find few 

 if any of this species of locust, but instead there occur two or three 



