CONCLUDING CONSIDERATIONS. 329 



development of a quite natural advantage, such an 

 extraordinary creature came by and by to be built up. 

 But is not the Benchuca, " the great black bug of the 

 Pampas," still more extraordinary ? Mr. Darwin speaks 

 of it thus 



" It is most disgusting to feel soft wingless insects, an inch long, 

 crawling over one's body. Before sucking they are quite thin, but 

 afterwards become round and bloated with blood, and in this state 

 are easily crushed. One which I caught at Iquique was very empty. 

 When placed on a table, and though surrounded by people, if a 

 finger was presented, the bold insect would immediately protrude 

 its sucker, make a charge, and, if allowed, draw blood. It was 

 curious to watch its body during the act of sucking, as in less than 

 ten minutes it changed from being as flat as a wafer to a globular 

 form. This one feast, for which the benchuca was indebted to one 

 of the officers, kept it fat during four whole months ; but, after the 

 first fortnight, it was quite ready to have another suck." 



One meal could keep this insect fat during four whole 

 months, how account by variation and application of 

 accident for such an extraordinary advantage ? 



The Pteroptochos albicollis is particularly amusing. 

 " It is called Tapacolo, or ' cover your posteriors,' " says 

 Mr. Darwin ; " and well does the shameless little bird 

 deserve its name, for it carries its tail more than erect, 

 that is, inclined backwards towards its head." On first 

 seeing the Turco, another bird of the same genus, " one 

 is tempted to exclaim, ' A vilely stuffed specimen has 

 escaped from some museum, and has come to life again ! ' 

 It really requires little imagination to believe that it is 

 ashamed of itself, and is aware of its most ridiculous 

 figure." How certain marine animals come to save 

 themselves from detection, some by emitting "a very 

 fine purplish -red fluid which stains the water for the 

 space of a foot around," and others by similarly " dis- 

 colouring the water with a dark chestnut-brown ink," 

 will give some trouble to the explanation by gradual 



