170 THE WOKLD OF LIFE 



size. The wing-coverts (elytra) of the beetle are reduced to 

 pointed scales, allowing the true wings to be always extended. 

 This is most unusual in beetles, as is the white band across 

 the wings in this order of insects (Fig. 23). This strange 

 and most unusual modification of an inoffensive insect, so 

 as closely to resemble one of another order which is protected 

 by a dangerous sting, can be explained in no other way than 

 through the advantage derived by the harmless beetle by be- 

 ing mistaken for the wasp. Of course, this change is the 

 result of a very long series of slight modifications of the beetle, 

 each bringing it a little nearer to the wasp, a series extend- 

 ing probably through thousands or even millions of genera- 

 tions.^ 



Becogniiion-Marlcs 



But though the subject of '^ mimicry " involves problems 

 of extreme complexity and interest, and has therefore at- 

 tracted the attention of numerous students, yet it is almost 

 entirely confined to the insect world, and, taken as a whole, 

 is not nearly so important a factor in the development of the 

 great Avorld of life as the class of " recognition "-colours of 

 which I will now give a short account. 



My attention was first directed to this subject during my 

 visit to south Celebes in 1856-57, where, during about six 

 months' collecting, I obtained the unusual number of fifteen 

 different birds of prey, of which the majority were of the 

 hawk sub-family. While skinning and preserving these birds, 

 and after my return home, wdiile determining the species, I 

 could not help observing in many of them the varied and 



1 Other cases are given in my Darwinism ; but those who wish to under- 

 stand the whole problem and what an important part it plays in nature 

 should read Professor Poulton's elaborate papers in the Transactions of 

 the Entomological Society of London for the years 1902 and 1908, together 

 with those of Dr. F. A. Dixey and other writers. There is also a very good 

 article by Mr. E,. Shelford, on mimetic insects from Borneo, and as these 

 are illusttated by coloured plates and deal with cases of the same nature as 

 the one here given, they are very instructive. (See Proceedings of the 

 Zoological Society of London, Nov. 4, 1902.) 



