180 PROTECTIVE RESEMBLANCE IN ANIMALS. 



so high up in the animal kingdom. Most of our readers; 

 are probably acquainted, at least by name, with those 

 lowly South American mammals known as sloths. These 

 animals are inhabitants of the great forest regions of that 

 continent, and are of a sombre greyish colour, very like 

 that of the gnarled and lichen -clad boughs from beneath 

 which they are wont to hang back- down wards. Not only r 

 however, is their general colour like that of a lichen- 

 covered branch, but their coarse grey hairs actually develop 

 a growth of lichens upon themselves to complete the 

 resemblance to their surroundings. It is, indeed, clear 

 that the long grey coat of the sloths has been produced 

 for the sole purpose of this protective mimicry, for when 

 this is removed there is found beneath an under-coat of 

 softer fur marked by yellow and black stripes, which may 

 be pretty confidently regarded as the original coloration of 

 these animals. 



We have now to consider animate, or true mimicry, in 

 which one animal imitates the form, and generally the 

 habits, of another in order to participate in the immunity 

 from foes enjoyed by the latter,owing either to the possession 

 of some formidable weapon, or to its unpalatable nature as 

 food. In all cases of this kind of mimicry it is essential 

 that the mimicked animal should be numerically far more 

 abundant than the niimicker, as otherwise predatory 

 creatures would soon learn that the innocuous and palatal 

 animal was as likely to be captured as the harmful 

 one. Undoubted cases of true mimicry are most common 

 among insects, and it is to these alone that our ob- 

 servations will be confined. We may also observe that 

 mimicking insects, as a rule, mimick other insects, although 

 it has been considered that some large caterpillars mimick 

 snakes, and certain moths certainly imitate birds. 



We will first refer to some excellent and well-marked 

 instances of mimicry which occur among insects of our own 

 country. Most of us are probably familiar with those large 

 hairy brown flies which may be seen in autumn creeping in 

 a sleepy sort of manner about the windows of houses, and 

 are commonly known as drone flies, and scientifically as 

 Eristalis. These insects, although true flies, with only a 



