MIMICRY IN BEETLES 237 



closely-related genus Diabrotica ' (I. c. p. 370). The latter 

 species are also mimicked by those of the allied genus 

 Dirccma. Mr. Gahan shows, furthermore, that eighteen 

 species of the genus Lema, belonging to a different Sub- 

 Family, closely resemble the species of Diabrotica (in 

 one case the allied genus Cerotoma) found in the same 

 localities in tropical America. In three cases species 

 of Neobrotica, and in one a species of Dircema, fall into 

 the groups thus formed. 



Mr. Gahan is disposed to regard the resemblance of 

 the species of Lema, together with that of the Longicorn, 

 Oxyly mma gibbicollis, for a species of Diabrotica, as an 

 example of Batesian Mimicry. Future observation and 

 experiment must decide upon this as upon so many other 

 cases concerning which we are uncertain whether to adopt 

 the Batesian or the Mullerian interpretation. The ten- 

 dency of recent observation, however, strongly favours 

 the opinion that the latter theory will explain a much 

 larger number of resemblances than the former. 



But whichever interpretation be ultimately adopted, 

 the fact remains the same -that the resemblances in the 

 Coleoptera are of the same character as those in the 

 Lepidoptera, and are, like the latter, independent of 

 affinity. They are readily to be explained by the opera- 

 tion of a theory of selection, but present the same 

 difficulties as those presented by the Lepidoptera to an 

 interpretation by any other theory as yet brought forward. 



6. The Resemblances in question are not accompanied by 

 any changes in the direction of the Mimicked Species 

 except such as assist in the production or strengthening 

 of a Superficial Likeness. 



This argument is fatal to any theory as yet advanced 

 except one based upon the principle of selection directed 

 to a definite end, viz. the production of resemblance. It 

 is impossible to explain why external forces or internal 

 forces should thus act upon a certain set of characters 

 whose only relationship is that they tend to produce 

 a superficial likeness to another species that they should 



