\D\I'II\I iTION 



197 



frequent \nother pper r tin- same 



. UFS <mly on n.< 1. -urfa. C , either bare or li< hen 



crusted. Thi Mottled with several colon but e pecially 



yellow, black and ijrecnM when tlyin.ir but indi 



able when resting on a patch of lichen- I ig .'46 It). \Vh- 

 hopper OCCUT8 amon.n lichen covcrc<l rocks, 'illiem Illin- 



not alight by hai)ha/ard as a rule, but habitually llie.- from one 

 patch of lichens to another. 



Instances such as lhi> jive support to the opinion that "prote- 



' are not always merely accidental occurrences; since the 

 live color- are rendered effective by special habits of the insect. 







}6. Trimerotropis saxatilis. A, with wings of right side spread. B, with wings 

 closed, and resting on lichens. Natural size. 



This particular grasshopper, it may be added, is sluggish, and inclined 

 to remain where it alights an advantageous habit under the circum- 

 stances. The case is not so simple as that of a caterpillar that is green 

 simply because it feeds on chlorophylls. 



Adventitious Resemblance. If, instead of hastily ascribing all 

 apparently of protective resemblance to the action of natural 

 ion, one inquires into the structural basis of the resemblance in 

 each instance, it is found that some cases can be explained, without the 

 aid of natural selection, as being direct effects of food, light or other 

 primary factors. Such cases, then, are in a sense accidental. For ex- 

 ample, many inconspicuous green insects are green merely because 

 chlorophyll from the food-plant tinges the blood and shows through the 

 skin. If it b. ! that natural selection has brought about a thin 



and transparent skin, it may be replied that the skin of a green cater- 



