3 2 4 THE PLACE OF MIMICRY 



to assume a position in which their characters are dis- 

 played to the full. Thus Portschinski has shown that 

 the two unpalatable English moths Spilosoma urticae* 

 and 6". mendica*, female, when disturbed, assume attitudes 

 which serve to display their conspicuous yellow and black 

 colours. 1 In both types of so-called ' sham death ' — 

 Cryptic and Aposematic — a definite attitude is assumed, 

 which is not that of death. 



9. Warning or Intimidating Sounds. — Sound may be 

 employed as an Aposematic Character, as in the hiss of 

 snakes and some lizards. Certain poisonous snakes when 

 disturbed produce by an entirely different method a far- 

 reaching sound not unlike the hiss. Thus the Rattle 

 Snake (Crotalus) of America rapidly vibrates the series 

 of dry, horny, cuticular cells, movably articulated to each 

 other and to the end of the tail. The stage through 

 which the character probably arose is witnessed in 

 another genus which vibrates its tail among dry leaves 

 and thus produces a warning sound. The deadly little 

 Indian snake, Echis carinata (the ' Kuppa ') makes a 

 penetrating swishing sound by writhing the coils of its 

 body one over the other. Special rows of the lateral 

 scales are provided with serrated keels which cause the 

 sound when they are rubbed against each other. Large 

 birds, when attacked, often adopt a threatening attitude 

 accompanied by an intimidating sound which usually 

 suggests more or less closely the hiss of a serpent, and 

 thus includes an element of Mimicry. 



10. Intimidating Attitudes. — The Cobra warns an 

 intruder chiefly by attitude and by the broadening of its 

 flattened neck, the effect being heightened in some 

 species by the 'spectacles'. In such cases we often 

 witness a combination of Cryptic and Aposematic 

 methods, the animal being concealed until disturbed, 

 when it instantly assumes a Warning attitude. 



The benefit of such intimidating characters is clear: 



a venomous snake gains far more advantage by terrifying 



than by killing an animal it cannot eat. By striking, 



the serpent temporarily loses its poison and with this 



1 Zepidopterorum Rossiae Biologia, St. Petersburg, 1890. 



