Mimicry 323 



the brown pigment, but, if protection by warning 

 colours be a fact, it is easy to understand how the 

 individuals in which it was most strongly developed 

 were favoured in the struggle for existence. Among 

 the South American Pieridee which resemble Heli- 

 coniince a number of stages in the wing-pattern can be 

 traced between the normal black and white or yellow 

 species of the family and the perfect mimics (l86). 



Besides this mimicry of protected insects by harm- 

 less species, there is mimicry within the protected 

 groups themselves. All Heliconiinae have an easily 

 recognised and characteristic aspect, and a large sec- 

 tion of the Ithomiinoe in South America have assumed 

 an aspect so similar that they were formerly classed in 

 the same sub-family. Further, it is found that within 

 this characteristically marked section certain species 

 closely mimic other species of different genera. It is 

 believed that a certain number of nauseous insects 

 must fall victims to young insect-eating animals which 

 have to learn by experience that "warning colour" 

 and distastefulness go together. By reducing the 

 number of "warning" patterns the education of the 

 young birds and lizards to the advantage of the butter- 

 flies is made easy, a smaller proportion of insects being 

 tried and rejected in a crippled or dying condition. 

 And it is clearly of advantage to a rare protected 

 species to resemble a common one, since the large 

 majority of individuals of the two species which arc 

 sacrificed will necessarily be drawn from the former. 



But considerable doubt has recently been thrown 

 on the whole theory of mimicry, and attempts have 

 been made to explain the facts just mentioned as the 

 result of "accidental" causes or as the effect of 

 similar surroundings on insects inhabiting the same 

 districts (187, 188). The likeness which some insects 

 bear to others from different geographical regions 



