1909] Mimicry in the Butterflies of North America 235 



examples of Mimicry from this part of the world. L. archippus 

 has been shown to be the result of a recent invasion, — its southern 

 and eastern forms to be still newer products of the changes in 

 archippus itself. 



The sensitiveness of the group is shown by the fact that, in 

 spite of this recent origin, all except astyanax are most beautiful 

 and striking mimics; and even astyanax is a better mimic than 

 lorqiiini. The fact that lorquini, the member of so sensitive a 

 group, is an undoubted mimic, but a very poor mimic, supports 

 the conclusion that the association with its model has endured for 

 but a brief period, a conclusion also supported by the diminution 

 of the resemblance outside the range of calif arnica. 



If the relationships which I have found to exist in the avail- 

 able material — in quantity very insufficient for such minute com- 

 parisons — if these are confirmed by extensive investigations in 

 America, it will follow that the resemblances between L. calif ar- 

 nica and L. lorquini will be one of the most interesting and instruc- 

 tive examples of Mimicry in the world. Its value will lie in the 

 early stage reached by the resemblance, together with the 

 diminution of the likeness in calif ornica to the south and, especial- 

 ly, in lorquini to the north. There is no reasonable doubt that 

 lorquini forms a single Syngamic community along the Pacific 

 Coast of North America, and we should therefore witness, first, 

 the marked strengthening of characters in an area of selection; 

 secondly, their transmission with diminished effect into other 

 areas. 



If what I have observed be the phenomena presented by the 

 growth, at an early stage, of a mimetic likeness in lorquini, then 

 that growth is "continuous" and transitional to the last and 

 finest degree. 



It is perhaps appropriate to' state in a few lines how we may 

 imagine that the selection of minute characteristics such as the 

 presence or the position of a single spot may be made. We 

 ourselves may observe that one individual butterfly is a better 

 mimic than another. We may then analyse the pattern, as I 

 ha\'e attempted to do in this address, and realize that the 

 improvement is due to differences in one or more relatively minute 

 elements. Recognizing the cause of the change, we are perhaps 

 prone erroneously to suppose that enemies recognize it also and 

 that selection has been brought to bear directly and consciously 

 upon it. Such a view is almost certainly wrong. The only pro- 



