98 NATURE SKETCHES IN TEMPERiTTE AMERICA 



body give to the insect an elongated, roi^nded form which is 

 very characteristic. 



The protective resemblance of these hioths in the manner 

 shown might be ascribed by some to mere coincidence. But 

 when one studies the subject carefully the measure of resem- 

 blance is so detailed that some especially adaptive cause is 

 demonstrated. Here there seems to be exercised a selective 

 factor that cannot be ignored, picking out the best imitations 

 in the face of more highly discriminative perception of those 

 enemies against the depredations of which this type of pro- 

 tection is developed.' 



' Under the title of "The Disguises of the Cresphontes Caterpillar," I have 

 shown that this larva imitates bird droppings, so this is by no means an uncom- 

 mon form of protective resemblance. 



