INSECTS 241 



mimicking forms are edible, and that they escape destruction 

 by deceiving the enemies which would devour them if they 

 were not disguised. Yet strange to say this assumption has 

 never been tested. It may be perfectly true that mimicking 

 forms often belong to edible and much persecuted families, 

 but it is by no means certain that a form which has acquired 

 the dark or conspicuous colours of another inedible species 

 owes its safety entirely to its deceptive appearance. Inedible 

 forms, such as the Heliconidse, the gooseberry caterpillar, and 

 others are distasteful largely in consequence of the presence 

 of the pigments which make them conspicuous. Therefore 

 when a mimicking form acquires similar pigments it probably 

 likewise ceases to be palatable to insect eaters, and would be 

 equally unmolested even if it possessed no particular resem- 

 blance to a species of another family. The theory of specific 

 mimicry involves assumptions that have not been sufficiently 

 realised. It assumes that birds or other enemies of butter- 

 flies are as precise in entomological discrimination as the 

 human specialist. Consider, for example, the cases in which 

 special varieties of the imitating form are associated with 

 special varieties of the imitated in different localities. The 

 differences between the varieties require careful examination 

 to be perceived, even an entomologist would not distinguish 

 them as varieties if he studied them only alive in their 

 natural conditions. Suppose that the mimicking edible form 

 had only one variety in both localities, and the pattern form 

 had two. Is it conceivable that a bird or lizard would 

 perceive the slight discrepancy in the second locality, and 

 would pick off the individuals of the edible form which had 

 not a sufficiently exact resemblance to the markings of the 

 second variety of the inedible form ? If we are to suppose 

 that this takes place we have also to suppose that the bird 

 or lizard knows a particular variety of an inedible species 

 and does not molest it, but attacks the individuals of an 



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