Aposematic Sounds 
no birds. When these came into being and 
began to prey upon insects, the conspicuously 
coloured species which were not inedible or 
very unpalatable would soon become extinct, 
while those that were inedible would survive as 
warningly-coloured insects. In other cases it is 
not improbable that these warningly-coloured 
creatures have arisen by mutations from more 
soberly - hued insects. It is conceivable that 
every now and again a mutation occurs which 
renders its possessor conspicuous. This will 
result in the early destruction of these aberrant 
individuals unless their newly-acquired gaudi- 
ness is either correlated with, or the result of, 
distastefulness. 
In the case of warning colouration, the Neo- 
Darwinians have, as usual, pursued their theory 
to absurd lengths. Professor Poulton, for 
example, extends it to sounds and attitudes. 
“Sound,” he writes, on page 324 of Essays on 
Evolution, “‘ may be employed as an Aposematic 
character, as in the hiss of some snakes and some 
lizards. Certain poisonous snakes when dis- 
turbed 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 
223 
