In some cases these brilliantly coloured insects may be survivals of an age in which there were 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 gaudiness is either correlated with, or the result of, distastefulness. Aposematic Sounds 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 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. . . . 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 attitudes 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 a reserve of defence. Furthermore, the poison does not cause immediate death, and the enemy would have time to injure or destroy the snake.” Intimidating Attitudes