34 THE GEXESrS OF SPECIES. [Chap. 



semblance ^Ir. Wallace observes : ^ " Tropical insectivorous 

 birds very frequently sit on dead l»ranclies of a lofty tree, 

 or on tbose wbich overbanGj forest patbs, gazing intently 

 around, and dartino: off at intervals to seize an insect at a 

 considerable di>;tanee, witb wliicli tbey generally return to 

 tbeir station to devour. If a bird began by capturing tbe 

 slow-flying consjiicuous Ileliconida*, and found tbem always 

 so di.sagreeable tbat it could not eat tbem, it would after a 

 very few trials leave off catcliing tbem at all ; and tbeir 

 wbole a[)pearance, form, colouring, and mode of fligbt is so 

 peculiar, tbat tbere can be little doubt birds would soon 

 learn to distini^uisb tbem at a loni:^ distance, and never 

 waste any time in pursuit of tbem. Under tbese circum- 

 stances, it is evident tbat any otber butterfly of a group 

 wbicb birds were accustomed to devour, would be almost 

 equally well protected by closely resembling a TTeliconia 

 externally, as if it acquired also tbe disagreeable odour ; 

 always supposing tbat tbere were only a few of tbem 

 amouGT a i^reat number of Ileliconias. 



"Tbe approach in colour and form to tbe Heliconida^, 

 however, would Ix:* at tbe first a positive, tbougb perbaps 

 a slight, advantage ; for although at short distances this 

 variety would be easily distinguished and devoured, yet at 

 a longer di.stance it might be mistaken for one of the 

 uneatable group, and so be passed by and gain another 

 day's life, wbicb might in many cases be sufficient for it 

 to lay a quantity of eggs and leave a numerous progeny, 

 many of which would inherit tbe peculiarity which had 

 been the safeguard of their parent." 



As a complete example of mimicry ]\lr. Wallace refers 

 to a common Indian butterfly. He says:- "But the 

 J Loc. cit. p. 80. 2 ii,ij_ p 59 



