6 EANGE OF LEPIDOPTERA. [CH. I 



capricious occurrence of butterflies and moths ; we do not 

 now refer to marsh-loving or wood-loving species or to any 

 intelligible restriction of this kind. Out of a dozen fields, 

 to the eye equally well suited for the maintenance of a 

 given species of moth, in which for instance the food plant 

 is equally abundant, two or three or it may be only one 

 will be inhabited by the insect in question, which will 

 there perhaps swarm. Some years since a small moth was 

 found at Folkestone only in a particular tract of grass 

 with no obvious advantages — indeed the reverse, as it was 

 scanty and trodden under the feet of passers by — to the 

 exclusion of neighbouring grassy areas ; this insect, known 

 as Tapinostola bondii, was abundant in this particular 

 locality but nowhere else in the neighbourhood. In every 

 local faunal list such and such a wood or field is given as 

 the locality for a particular insect, which would be equally 

 at home in other woods and fields, but is not as a matter 

 of fact found in them. To get the particular insect we 

 have perhaps to journey to another county or even to 

 another part of England; possibly a particular wood is 

 the only part of England where it is to be met with and 

 the next locality will be on the Continent. No doubt 

 some of these apparently capricious variations are to be 

 explained by advancing civilisation. Building, draining 

 and the gradual reclamation of the country are fatal to 

 insect life as a rule. But this will not explain every case 

 of capricious restriction to a few separated stations, such 

 as are so commonly met with among the Lepidoptera of 

 this country. 



