262 



'rill-OKIKS OV MIMICRY 



rcscinhlancc is a direct cttcct of climatic or other forces 

 connected with locality, when the results are in reality so 

 utterly different and yet superficially so entirely ahke. 

 It is obvious that the methods !))• which the appearance 

 of a terminal thickening; is produced in the two mimics 

 ar(! as cssentialh" ditlercnt as are those by which the 

 appearance of short antennae is produced in the model 

 on the one hand, and its two mimics on the other. The 

 fact which rccpiires explanation is the extraordinary like- 

 ness in spite of the essential dilierence, and this, when it 

 is repeated a^ain and a<>^ain, cannot be interpreted ]>y any 

 theory unless based upon the principle of selection. 



Many other examples of the same kind could easily be 

 l^rouLrht forward : in fact, it mav be admitted as a o-eneral 

 |)rinciple that in Protective Mimicry and Common W'arn- 

 iuL,^ Colours the resemblance is ;iever attained b\' precisely 

 similar methods, and i/eneralK' bv methods which are 

 extremely imlike. I propose, in concludiuL^ this Section, 

 to discuss a few examples from the Lepidoptera, inasmuch 

 as the resemblances in question have been chiefly studied 

 in this j^roup, and because an explanation based on the 

 theor)' of b^xternal or on that of Internal Causes has been 

 soui^du more often and |)ressed more stron<;ly in the 

 Mimetic Lepidoptera than in any other Order. 



The Pierinac are specially liable to take on these 

 Resemblances. In tropical America they chiefly reseml)le 

 the Ithoniiinac, Hcliconinae, and rapilioniiiae, afford inij^ 

 some of the best and earliest recorded examples of 

 Mimicry (althoui^h Dr. V . A. Dixey has now shown that 

 they are more probably to be interpreted as Common 

 Warning: Colours). The chemical nature of the win<^- 

 ])ii;ments of the Pia inac has recentl\- formed the subject 

 of an interestiiiL; paper by V. Gowland IIoj)kins.^ The 

 author shows that the white j)ii;nient so common in the 

 group is an impure uric acid probably uncombined, that 

 the yellow and orange pigment is a derivative of uric acid 

 to which he gives the name Tepidotic acid*, while a much 

 rarer red pigment, less fully investigated, is probably of 



' Proc. Roy. Sor.j Ivii, 1894, p. 5, ar.d /V//7. Trans., 1895, 13. j». 661. 



