522 COMMISSION OF ERROR. 



ablest and best-known entomologists, is a more beautiful, 

 though scarcely more interesting example. The crocodile and 

 alligator are mistaken for floating tree-trunks by unwary 

 animals drinking on the banks of tropical rivers, and they 

 sometimes pay by loss of life the penalty of their error. On 

 the other hand, insects sometimes so closely resemble the 

 droppings of birds, or spiders the axillary buds of plants, as 

 to throw birds off their guard ; thus enabling these protected 

 insects and spiders to escape the usually keen vision of their 

 bird enemies. The seed vessels of medicago polymorpha 

 sometimes resemble caterpillars, and are mistaken for cater- 

 pillars by birds ; while the seeds of calendula (marigold) also 

 resemble a hairy caterpillar, and may thus deter some birds 

 from preying upon them (Erasmus Darwin). 



