THE THEORY OF MIMICRY 14o 



m-e included some tliat possess distasteful properties, 

 affords to all a measure of protection against the attacks 

 of young- and inexperienced birds which soon recognise 

 them as a group to be left alone. 



As I have tried to show above, and as actual evidence 

 has proved, distastefulness with its accompaniment of 

 warning colours, can onh' be claimed as affording a 

 measure of protection to butterflies against the attacks 

 of birds. Therefore if the warning colour hypothesis is 

 to hold good, it must be proved that the depredations of 

 birds are sufficiently severe to influence the trend of evo- 

 lution. Tliere is ample evidence to prove that some in- 

 sectivorous birds, at least occasionally, prey upon butter- 

 flies (the order which has been most quoted in support 

 of mimicry), but have we sufficient evidence to show that 

 the losses sustained by these attacks are of such severity 

 as to determine the direction of variation? Dr. D. 

 Sharp, in "Cambridge Natural History — Injects/' Part 

 II, page 34.5, has the following: — '' It is possible that the 

 odour and taste (of the Danaides) are of some value to 

 the insects; as, however, butterflies of any kind appear 

 to be but rarely attacked by birds, and as their chief ene- 

 mies are parasitic insects which attack the larval instar, 

 it is impossible to consider this protection of the prime 

 importance to the species as many theorists assume it to 

 be.'' 



Monsieur H. Fabre, Capt. Selous and many other field 

 naturalists, myself included, have not observed a single 

 case in which a bird has flown at and captured a butter- 

 fly. 



I must add that I have on numerous occasions observed 

 birds of many species, including bulbuls, flycatchers, and 

 other insectivorous feeders, flitting about in close prox- 

 imity to butterflies flying past, or hovering over flowers, 

 and they appeared not to take the slightest notice of 

 them. 



Some others have been more fortunate, but the con- 

 firmatory evidence is so meagre as not to justify more 

 than the statement that birds occasionally prey upon 



