372 THE BIOLOGY OF INSECTS 



families or sub-families quite distinct from the noxious 

 insects, resemble them so closely in general aspect that they 

 may be regarded as " mimics," and by means of the mimicry 

 it is believed that their aspect deceives insect-eating creatures 

 which accordingly leave them alone, although they are 

 innocuous and edible. It is also v^ell known that noxious 

 insects of one group may be '* mimics " of members of 

 another ; many species of tropical American Heliconiinae 

 are closely like species of Ithomiinae inhabiting the same 

 districts. This type of mimicry was first distinguished by 

 F. Midler (1879), who explained the advantage derivable 

 from these resemblances between protected forms as 

 being " the division between two species of the percentage 

 of victims to the inexperience of young insectivorous 

 enemies, which every separate species, however well pro- 

 tected by distastefulness, must pay " (R. Trimen, 1897). 

 A " mimicking " species less abundant than its model 

 will only pay toll in proportion to its numbers in any 

 area, as compared with the heavier mortality suffered by 

 the commoner species from the attacks of insectivorous 

 creatures. Another remarkable fact about mimicry among 

 butterflies is that it may be restricted to the female sex ; this 

 is well illustrated by nymphaUnes of the genus Hypolimnas 

 in the eastern tropics, whose males are of the aspect typical of 

 their group, while the females mimic various Danainae, and 

 also by the African Papilio dardanus^ which, besides a typical 

 form of female resembling the male in her cream and black 

 ** tailed " wings, possesses various '' untailed " female forms 

 each a close mimic of some Danaine or Acraeine butterfly 

 inhabiting the same district. 



Mimicry among insects, and especially among butter- 

 flies, has been prominent during recent years in discussions 

 between naturalists of the Darwinian school who uphold 

 the theory of natural selection and others, like R. C. 

 Punnett (1915), who contend that mimicry has no adaptive 

 meaning and that it can be explained by the influence 

 of the surroundings or by the inheritance of mutations on 

 Mendelian principles. That inheritance among the poly- 



