72 



NATURE SKETCHES IN TEMrERATE AMERICA 



These colors are often produced by pigment and strias in the 

 same scales of butterflies. 



The laws which Wallace l^elieved governed the production 

 of all cases of i^rotective resemblance were rapid multiphcation, 

 incessant, slight variation, and the survival of the fittest, in 

 other words, natiu'al selection. Those eases which furnish 

 striking exami)les of protective resemblance, such as the walk- 

 ing-stick and leaf-like insects, re])resent instances in which the 

 process of modification has been going on during an immen.sc 

 scries of generations. The great majority of such species 

 occur in the tropics w'here tlie conditions of existence are most 

 favorable, and where climatic changes have for long periods 

 been hardly perceptible. 



. \ The Tkee Toad 



'M.rT':\.._ ^1 



' ''- ^' -^ . 



T CARCETjY a week passed during 

 ..i spring and summer that I did 

 not come across the tree-toad in 

 my walks afield. In April its 

 song was heard at twilight, 

 emanating from the lowlands at 

 the })order of ponds, ditches, and 

 wet meadows, or from the shrubs 

 and trees nearby. During sum- 

 mer, one of its favorile places of 

 i-clreat in the daytime was in the 

 > shade of the wooden rafters under 



the roof of a neighbor's porch. Again, 

 the little pockets on the trunks of beech 

 trees in the woods were especially attractive places 

 for them. In September, the openings into the old apple 

 trees often afforded choice locations in which they took up 



