-112 THE ENTOMOLOGIST. 



■practice was first discovered actively at work in the economy of 

 Nature among certain groups of Lepidoptera in South America. 

 Since then, however, we have inckided mimicry in a wider term, 

 and call it only one form of assimilative coloration. Now it is 

 quite certain that in the realms of Entomology we meet with by 

 far the most striking instances of protective resemblance, both 

 in colour and form. Formerly this principle was supposed to be 

 generally tropical in its manifestations, and it was thought 

 sufficient to cite as instances the Heliconid imitative Pieridje of 

 Brazil or the stick-like MantidsG of India. Now we know that 

 this specialization of colour and form pervades all Nature, and 

 is as common, although not so theatrical in its developments, in 

 Europe as under the Equator. We, moreover, distinguish be- 

 tween its manifestations ; there is the defensive and the aggressive 

 kind ; there is the simply passively protective, as in the case of 

 Geometrid larvae or the majority of our British Rhyncophorous 

 Coleoptera; or actively defensive and minatory, as the wasp 

 beetle, or the larva of Choerocampa djyenor. Of this protective 

 kind of resemblance there is a perfect cloud of witnesses among 

 insects. Protection by colour for aggressive purposes or conceal- 

 ment for attack seems less frequent ; but there are many instances 

 of it, both in its concealing and alluring phases, among the 

 Arachnida. Some assimilative coloration also serves a double 

 purpose, as in many of the Hydradephaga (the water beetles), 

 and conceals the insect as well from the perch, its enemy, as 

 from the smaller beetle, its prey. 



This is a very wide and a deeply interesting line of research ; 

 and I have dwelt upon it for a moment, familiar as it is to all of 

 us, because it exhibits examples not only of some of the best 

 evidence supplied by Entomology in support of evolution, but 

 also of some of the most serious difficulties that theory has had 

 to contend against. For it must by no means be assumed that 

 because the evolutionary theory of life has found a general 

 acceptance among all modern scientific thinkers, that therefore it 

 can solve all problems that Biology can offer to it. The courses 

 of most great theories have similar features. A great mind 

 evolves and enunciates some luminous generalization ; it explains 

 so much that the vast illogical, inaccurate, public fancies that it 

 explains all, and it meets with a triumphant acceptance. Then 

 the wise men, generally German professors, turn and seek to 

 rend it, dissect its premises, prove it with hard questions, follow 

 its deductions to their remotest conclusions, and find perhaps 

 that some of its assumptions are too hast}^ some of its sup- 

 porting evidence feeble or irrelevant, and the real battle begins. 

 Sometimes the great theory falls incontinently to pieces, like 

 that of the Arj^an race and their Asiatic home ; far more rarely, 

 hke that of the Copernican system of the heavens, it emerges tri- 

 umphant from every ordeal, and becomes thenceforth axiomatic. 



