debris, or like parts of moss-draped or ragged-barked boughs or trunks. So 

 travelers have said, and in this case there seems to be no reason to question 

 their interpretation. Sloths vary widely in color, but a rich olive-brown is 

 perhaps the most characteristic tint. Sometimes they are almost green, owing 

 to a growth of minute algae on their fur; and this of course enhances the mimetic 

 effect, allying them in the very ingredients of their superficial structure to the 

 vegetable masses all about them. Again, they are sometimes rather brightly 

 varied with patches of dark brown, blackish, dull orange and yellow, and even 

 white; but these markings barely attain the rank of true 'ruptive' patterns. 

 One marking, however, to which they are very prone, is extremely interesting 

 and noteworthy. This is the blackish stripe or spot on the fore-back, sur- 

 rounded by a rim of light color, varying from orange brown to white. Strangely 

 enough, this marking is almost precisely duplicated on the head of a species 

 of sphinx-moth larva (see Plate XV, Fig. T, Chapter XXV) and it there plays 

 an important and unmistakable part in the imitation, beautifully achieved by 

 the aspect of the entire caterpillar, of a pendant, curled-up, brown dead leaf. 

 The larva hangs head downward, and its white-rimmed black spot pictures 

 the shadowed hole at the tip of the pendant leaf -roll. There seems very little 

 room for doubt that a like effect is achieved by the peculiar shoulder-spot of 

 the sloth. Evidently, this simulates a shadowed orifice, with brightly con- 

 trasting outward rim, in the bottom of the vegetable mass mimicked by the 

 entire beast. (See also page 157 of Chapter XXII, and Fig. 120.) 



The armadillos {DasypodidcB), another family of edentates, are terrestrial 

 and fossorial, and almost hairless. But they are partially protected from 

 their enemies by a hard, annulated shell, as well as by their prodigious dig- 

 ging-powers. Some species roll up into almost invulnerable balls, as do 

 their African and Asiatic relatives, the armor-scaled pangolins (Manidce). 

 Both these families, besides being chiefly nocturnal, belong perhaps to the 

 group of specially protected animals (although their armament is purely and 

 passively defensive, like that of tortoises, and unlike that of porcupines), and 

 their protective coloration accordingly is meager and irregular. Armadillos 



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