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V. Birds as a Factor in the Prochtction of Mimetic 

 Bescmhlances among Butterjiies. By Gur A. K. 

 Marshall, F.Z.S. 



[Read March 3id, 1909.] 



The question whether birds do, or do not, prey upon 

 butterflies to any appreciable extent is one which has 

 from time to time engaged the attention of Entomologists 

 for some years past. For it has been contended that the 

 validity of the theories of mimicry enunciated by H. W. 

 Bates and Fritz Mliller, as applied to butterflies, must 

 largely depend upon the production of adequate evidence 

 to show that these insects are liable to habitual attacks 

 upon the part of birds. Nor is it possible to deny the 

 reasonableness of such a contention, as soon as we en- 

 deavour to reconstruct mentally the processes which must 

 have been at work if those theories be true. 



Defences of Butterflies. 



In their imago state butterflies appear to be among the 

 most defenceless of insects, for their comparatively large 

 size and diurnal habits render them more or less con- 

 spicuous objects when on the wing, even though their 

 actual colouring may be dull and obscure. They have, 

 however, three principal lines of defence : (1) rapid or 

 tortuous flight ; (2) procryptic under-side coloration, 

 combined with the appropriate instincts for seeking con- 

 cealment; and (3) the possession of nauseous qualities 

 rendering them distasteful to a large proportion of their 

 enemies. 



The existence of these latter qualities has now been 

 experimentally proved beyond the possibility of cavil, and 

 we are probably justified in assuming that they occur in 

 all species of Danainae, Ithomiinae, Heliconinae, and 

 Acraeinae. They have also been shown to exist in certain 

 isolated genera of Nymphalinae, Lipteninae, Pierinae, 

 and Papilioninae ; but there does not appear to be any 

 real justification for the speculative assumption that they 

 are of general occurrence in these and other subfamilies. 



TRANS. ENT. SOC. LOND. ] 909. — PART IIL (SEPT.) Z 



