230 THE COLOURATION OF INSECTS 



abundant. In a brief preliminary statement in 1878 ^ 

 he says : " What advantage can it be to a creature pro- 

 tected by repellant odour to resemble another similarly 

 protected species ? If their foes avoid protected species 

 by * instinct,' none at all ; but if, on the contrary, as 

 appears so much more probable, the foes have to learn 

 their unpalatability by experience, then the benefit is all 

 the greater the less numerous the species. The advantage 

 gained by two unpalatable species by their resemblance 

 is in inverse ratio to the square of their numbers." 



This quotation may be amplified a little. A certain 

 number of lives of any species must be sacrificed in 

 teaching inexperienced enemies what to avoid. But 

 if the loss of insects of a certain definite aposematic 

 pattern, instead of being borne by one species only, could 

 be distributed over several resembling each other, the 

 loss borne by each species would be only a small pro- 

 portion of the total loss, while the lesson would be equally 

 well learnt. Moreover, it will be of further advantage 

 in that there will be fewer patterns to tax the enemy's 

 memory. 



So now we have to consider a second type of resemblance, 

 characterized by the presence of Common Warning Colours, 

 or, to use Poulton's term, Syn-aposematic. Although the 

 term " Mimicry," first used by Bates, should refer to 

 an edible species masquerading as inedible, it is loosely 

 used to cover the likeness between two distasteful species, 

 which is a matter of a different order. Properly speaking, 

 Mimicry is Pseud- and not /Si/w-aposematic. 



Instances of syn-aposematic resemblance may be seen 

 in England, such as the yellow and black bands of different 

 kinds of wasps, or the red and green of the Burnet moths. 

 These insects being so closely related, it may with reason 

 be argued that it is not surprising that Burnet moths 

 of a single genus should have a close similarity. 



* See Proc. Enl. Soc. Lond., 1915, pp. xxii, xxiii. 



