

JOURNAL OF VARIATION. 



Vol. XI. No. 2. February 15tii, 1899. 



Lepidoptera with a general inland distribution in Europe but 

 confined to coast habitats in England/^ 



By T. A. CHAPMAN, M.D., F.Z.S., F.E.S. 



The fact that certain lepidoptera have a general inland distribution 

 in Europe, but are confined to coast districts in England, is one that 

 occasionally comes up for discussion, but has never yet been satisfac- 

 torily nor completely explained. I propose, therefore, to brnig forward 

 such facts as I can, bearing on the question, in the hope that it may lead 

 to the matter being carried a little further, if not to the full elucida- 

 tion of all debatable points. The question is— Why do not certain 

 lepidoptera live inland with us as they do on the Continent ? As a 

 question of geo"-raphical distribution it is a minor one, and may m 

 some degree ^be'dealt with by itself, though being a particular case 

 depending to a great extent on general principles, it may be desirable 

 to refer to some'facts and principles that are outside the question itself. 



If we be'--in by askin"- why a particular species is found (or not 

 found) in a particular ^locality, we shall find the answers may be 

 sorted into two series corresponding to two aspects of the question of 

 distribution. The first series comes under the form, because i"^" some 

 reason or other it was able (or unable) to reach that locality. These 

 refer to the general question of distribution in great regions, in islands, kc. , 

 giving to each region its special fauna, such as the Palaearctic, Nearctic, 

 &c. This aspect ^of the question is quite outside the present discussion, 

 and all the answers we are in search of fall under the other series, and 

 take the form that the species does (or does not) exist m that parti- 

 cular locality because having got there (or been able to get there) it 

 found the circumstances of the locality were (or were not) suitable to 

 it. What then, are the circumstances of our coast that render it suit- 

 able to the insects contemplated in this discussion, and which do not 

 exist away from our coast, though they are to be found inland on the 

 Continent ? This apparently throws out of account the mfiuencc ot seii 

 air, a saline atmosphere, food-plants only found by the sea-shore, and 

 so on. We shall see, however, that this element cannot altogether be 

 left out of account, as it cannot be altogether separated from o her 

 elements which render it etiective. There is also the fact that m 

 England the coast line preserves some at least of the natural tcaturcs 



* Read to introduce discussion at the City of London Ent. Society, Jan. 3id, IStl'J. 



