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IX. The Geoyraphical FacLor in Mimicry. By F. A. Dixey, 

 M.A., M.D., F.R.S., Subwarden of Wadliam College, 

 Oxford. 



LRuad March 17th, 1020.] 



Plate VI. 



In endeavouring to interpret the remarkable phenomena 

 that are grouped under the head of Mimicry, it is important 

 to take hito account the fact that the forms resembling 

 each other are as a general rule to be found inhabiting 

 the same regions. This feature in the case has often 

 received conmient, and many illustrations have been 

 adduced of the close connection between similarity of 

 aspect and geographical proximity. The mimetic com- 

 binations of Heliconinae, Danainae, Ithomiinae and other 

 subfamilies, modified concurrently accordhig to their 

 respective habitats in various parts of the South American 

 contuient and the adjacent island of Trinidad, are well 

 known.* Other instances are certain " homoeochromatic " 

 assemblages hi the Oriental region, each comprishig repre- 

 , sentatives of the Danaine, Pierme, Papilionine and occa- 

 sionally the Satyrine subfamilies. These are only a few 

 of the cases that have come to light, in which a geographical 

 modification of a dominant form or forms has been reflected 

 in a corresponding alteration in the aspect of the associated 

 mimics. 



The bearing of the facts here referred to on the question 

 of the origin of mimicry is obviously of great significance ; 

 and it may be not superfluous to add a few more instances 

 of the kind which have not hitherto met with detailed 

 treatment or illustration. One such case is that of the 

 parallelism between the genus Prioneris and certam species 

 of the genus Delias, both of these genera being Pierines, 

 though not closely related in affuiity. So long ago as 

 the year 1867 this parallelism was noted by Mr. Wallace, 

 and subsequent hivestigation has tended not only to con- 

 firm, but also to extend his conclusions. Some of the 

 mimetic pairs are figured on Plate VI; figs. 12, 14, and 16 

 showing the species of Delias, and figs. 13, 15 and 17 the 



* See Poulton, " Essays on Evolution," 1908, pp. 272, 273. 

 TRANS. ENT. SOC. LOND. 1920. — PAETS I, II. (jULY) 



