290 THE ENTOMOLOGIST. 



exceedingly scarce, Arachnida — which, by the bye, are eminently 

 characteristic and abundant in the Alps — being the only enemies 

 of any consequence. The same thing also exists in boreal regions. 

 This, then, accounts for the superabundance of certain species, 

 which are permitted to multiply without any check except what 

 they receive from adverse climatal influences. At the same time 

 this immunity from attack does not favour the rapid evolution of 

 new forms. Climnte is probably the most important factor in the 

 production of new species in the Alps and in other portions of the 

 Palsearctic area. To put the matter in a nutshell, great competi- 

 tion favours the evolution of species, while little competition 

 produces individuals. 



It may probably be admitted that nature always permits the 

 production of the greatest number of individuals in a given area 

 which are capable of existing in it, so that, all other things being 

 equal, a new species can only come into existence by wholly or 

 partially crushing out one or more other species. Competition 

 generally being the greatest between closely-allied forms, those 

 which are the most nearly related to it are in consequence princi- 

 pally affected by any change in the equilibrium. Supposing ten 

 different species to exist in a certain district possessing an average 

 of 1000 specimens apiece, which means that the locality is capable 

 of supporting 10,000 individuals, the evolution or immigration of 

 one new species would upset the former balance entirely, for then 

 there would be eleven species, with a reduced average of about 909 

 individuals per capita, the total number, as I have remarked above, 

 remaining tlie same. The addition of ten new species would give 

 an average of only 500 to each, and so forth. 



These, then, are the principal answers which, in my humble 

 opinion, can be supplied in elucidation of the problems connected 

 with the relative large percentage of specimens to species of 

 Rhopalocera in the Alps in comparison with their proportions in 

 the tropical regions of the earth. 



Birmingham, October 18tb, 1895. 



CALLIMORPHA HERA IN SOUTH DEVON. 

 By W. Hewett. 



Whatever doubts may have existed with regard to the 

 genuineness of C. hera as a British species, there need be 

 none as to its occurrence in South Devon at the present time. 

 I have reliable evidence of more than one hundred specimens 

 having been taken there this season, of forty-eight of which I have 

 become the proud possessor. Twenty-five of these were taken 

 by myself and two by my wife whilst in the district last August; 

 the remaining twenty-one were all brought to me alive, mostly in 



