MIMICRY INDEPENDENT OF AFFINITY 235 



5. Resemblances even luithiu the Limits of an Order are 

 entirely independent of Affinity, 



The entire Independence of affinity is specially well 

 seen in the groups of convergent moths and butterflies 

 which are found in different localities in South America. 

 Although the resemblance is clear enough throughout all 

 the members of a large group, it is far closer between 

 certain species than others. When these are examined 

 they are found to be not more nearly related than other 

 members of the group, but frequently the reverse. Thus 

 it is very common for a species of Heliconins ^ to resem- 

 ble with the most remarkable precision a species of 

 Melinaea or some other Ithomiine genus in its locality. 

 Such resemblance is in these cases far closer than that of 

 the former to the species of the other genus [Eueides) in 

 its Sub-Family, and than that of the latter to any species 

 of the numerous related Ithomiine genera. Thus, to 

 illustrate this conclusion from some examples In the Hope 

 Collection, in Honduras by far the strongest resemblance 

 is to be found between a Heliconins and a Melinaea ; and 

 this is also the case (both species being different) in 

 Surinam. In Trinidad the resemblance is closest between 

 a Heliconins and a Titkorea, another Ithomiine. 



Under the theory of Natural Selection this association 

 is readily explicable. The pairs which thus form the 

 centres of local groups are probably the dominant forms, 

 relying more completely than the other members upon 

 the defence afforded by their w^arning colours and the 

 associated unpalatabillty. As a matter of fact there is 

 some evidence for their exceptional abundance as com- 

 pared with the other members of their groups. Again, 

 they are usually more nearly of the same size than the 

 other members, so that the perfection of the resemblance 

 In colour and pattern is aided by resemblance in another 

 quality. 



The theory of External Causes entirely fails to account 



^ Although united by Bates in the Family Heluomdae, the Heliconinae 

 and the Ithomiinae are Sub-Families lying at the very opposite ends of the 

 great group of Nymphalid butterflies. 



