114 Mr. G. A. K. Marshall on Diajwsematism, rvith reference 



Heliconins, being an ordinary plain white insect with a 

 moderate black border. On the other hand, in a position 

 of rest this marking would be concealed, and it is there- 

 fore difficult to understand what mimetic value it could 

 have. But it is only fair to point out that when the above 

 proposal was made the true $ of P. locusta was not known, 

 the $ figured by Dr. Dixey (/. c. PL VII, fig. 7) belonging 

 really to P. tithoreides, Butl. Now the real $ of locusta, 

 which is evidently a rare insect, docs present a fair general 

 resemblance on the upper-side to H. c. galanthtcs. For the 

 whole of the hind- wing and the basal part of the fore- wing 

 have been very much darkened and thus present a like- 

 ness to the similar dark blue areas in the Heliconius. We 

 need not therefore labour the point as to the mimicry of 

 locusta ^, but may merely consider whether it is reasonable 

 to suppose that the white patch on the upper-side of the 

 fore-wing of i7. cydno and its numerous varieties has been 

 produced by their directly mimicking locusta ^. 



The first point is the qiiestion of unpalatability. In 

 the cases previously discussed there do appear to have 

 been reasonable grounds for suggesting that the Pierines 

 involved were distasteful. Here there appears to be none. 

 Thus a 2'>Tiori it seems extremely doubtful that a scarce $ 

 Pierine, of questionable unpalatability, should have been 

 able to profoundly modify the colouring of both sexes of 

 an undoubtedly nauseous and abundant species such as 

 H. cydno. The crux of the whole argument lies in the 

 assumption that white colouring is abnormal in Heliconius 

 and must therefore be due to Pierine influence. Now 

 Riffarth and Stichel recognise 9 sub-species and 5 sub- 

 sidiary forms of cydno. Of these 7 have a conspicuous broad 

 white border in the hind-wing; 3 have this border of a 

 yellow colour, and 4 (including gcdcmihus) have no distinct 

 border at all. It seems probable that the borderless 

 galanthus-Wke forms represent the older type, of which the 

 much commoner pale-margined forms are a more recent 

 development. The hind-wings of these latter insects are 

 quite different from anything to be found among American 

 Pierines, and it can scarcely be contested that these broad 

 white margins have been developed by Heliconius cydno 

 and soplio quite apart from Pierine mimicry; and they 

 have again been independently produced in the very 

 different H. cyrhia. Further we may note that in Guiana 

 H. hecale presents a large white area in the fore- wing; 



