Mimetic Relationships in the genus Heliconius. 145 



able differences of internal anatomy and a slight, though 

 evident, external characteristic. 



It remains to consider certain points in connection with 

 the modifications which occur in various geographical 

 an as. Several exhibits have been made and papers read 

 on this subject. Mr. W. J. Kaye read a paper in 1906,* 

 in which he described and illustrated the many forms of 

 Melinaea, Heliconius, etc., forming a great characteristic 

 group in the Potaro District of British Guiana. In this 

 group were found to occur the following forms : — 



Nymi'haudae. 



Ithomiinae. 



Melinaea 4 



MecJmnitis 2 



Ceralinia 2 

 Heliconinae 



Heliconius 4 



Eueides 3 

 Nymphalinae 



Eresia 1 

 Danaidae 



Lycoreanae 



Lycorea 2 

 Erycinidak 



Lemoniinae 



Slalachtis 1 



together with the outlying members of the group not up to 

 that time actually taken on the Potaro, Tithorea harmonia, 

 Cram.. Protogonius hippona, Cram., Dismorjrfiia amphione. 

 The dominant member of the group was Melinaea 

 mneme, Linn., which occurred in " prodigious numbers." 

 The Heliconius forms were found to be by far the closest 

 mimics of the Melinaea, whilst at the same time they were 

 comparatively rare.f Great variation was observed in 

 the banding of the hind-wing from a narrow bar to almost 

 entirely black. A careful and interesting analysis is made 

 of the degree of blackening observed in the various forms, 

 with the result that there is found to be a closer agreement 

 on the underside than on the upper. Only two species 



* Notes on the dominant Mullerian group of butterflies from (lie 

 Potaro District of British Guiana. Trans. Hut. Sue. Lond., \>. 411 

 et seq., 1906. 



t See also Proc. Ent. Soc., p. liv. 1903. 



TRANS. ENT. SOC. LOND. 1916. — PART I. (AUG.} L 



