48 LEPIDOPTEROUS FAUNA OF PORTLAND. 



necessary that the particular food plant should be present in order 

 that the moth may exist in any locality, and causes which destroy 

 the food plant will, therefore, also destroy the moth, as well as other 

 causes which act primarily upon the moth. On the other hand, 

 the seeds of the plant may be transported to a distance by various 

 causes, such as birds, ocean currents, &c., which would not affect 

 the moth, so that in the new locality the moth will not be found. 

 The distribution of the moth will, therefore, give much more reliable 

 evidence as to the past history of the locality than that of the 

 plant. I must confess, however, that I do not see any sufficient 

 reason why the moths which are peculiar to Portland should not 

 occur in other places in this country nor can I suggest any reason 

 why, if they formerly occurred in other places in this part of the 

 world, as is, I suppose probable, they should have died out else- 

 where and survived at Portland. It seems to me that very 

 extensive experiments in the way of introducing these moths into 

 other localities apparently like Portland and observing the results, 

 might possibly enlighten us on this subject. 



I propose now to mention individually some of the moths which 

 are more or less peculiar to Portland, with a few remarks on each, 

 after saying a little about the entomology of the place generally. 



Portland has got a very bad name amongst entomologists, partly, 

 probably, from the experience of those who have come knowing 

 nothing of the locality and gone away with very little success, as they 

 would in that case be likely to do, partly from the weather, which 

 is often bad and generally uncertain if the wind is from a fairly 

 warm quarter, and partly from the very rough nature of the ground, 

 which is certainly inconvenient, not to say dangerous, especially in 

 night collecting, not to mention the pleasures of being pelted by 

 small boys from the top of the cliff with stones and other missiles, 

 and occasional attacks by coastguards and sentries. It is certainly 

 a bare and unpromising looking place, with scarcely any trees 

 upon it, except the small clump at Pennsylvania, so that it is 

 rather surprising to find that there exist on it at least 570 out 

 of about 1,400 Dorset, and about 2,100 British species of 



