NOTES ON THE DISTRIBUTION OF THE BRITISH COLEOPTERA. 295 



the few records we have being the result of a brief sojourn, at perhaps 

 not the best time of year, by one or two coleopterists, and it is more- 

 over, probable that these islets are far too small and too exclusively 

 marine to have successfully maintained any lingering relics of a fauna 

 which must have been at the time of their union with surrounding land 

 areas quite inland in character. Hence their evidence even if far more 

 exhaustive than it is at present might not be of much value. Enough, 

 however, I believe remains in the south of Ireland and western exten- 

 sion of England, to make it clear that their present coleopterous (and 

 other) inhabitants, could never have been derived from the east, but 

 are probably the survivals of some last Atlantis long sunk beneath the 

 waves of the western ocean. 



In drawing these speculations to a close I must admit that perhaps 

 the most obvious fact about them is their extremely provisional 

 character. We really know so little about the coleoptera of these 

 Islands, such vast areas still remain either absolutely unexplored or 

 known only from the results of a few days spent possibly during an 

 unpropitious season by the vagrant coleopterist. 



Beetles differ much from lepidoptera in the attention they have 

 received at the hands of entomologists and many of their species are 

 so minute and so elusive that nothing but persistent collecting 

 carried on for several years in any locality could hope to even 

 approximately exhaust its coleopterous inhabitants. This is precisely 

 what we lack. Coleopterists are few in number and principally 

 inhabitants of large towns, and it must be confessed, often more 

 prone to visit, for collecting purposes, localities known as likely to 

 furnish additions to their cabinets, than to explore more virgin fields 

 whose possibilities may be all unknown. Moreover, coleoptera share 

 with other orders of insects a most perplexing irregularity of appear- 

 ance and abundance. It is within the experience of every entomologist 

 that species of all orders have their " years," seasons when, owing to 

 causes probably exceedingly complex and often indirect, but which 

 are certainly quite beyond our present knowledge, a species will 

 abound throughout its range and often overflow its normal limits. 

 Such a spring tide of profusion is always followed by the ebb of 

 scarcity, and it is the mean of a long series of years which will fix the 

 true range limit of a species. Just as the occasional occurrence of 

 Calosoma ftycophmita during such favourable years along our southern 

 coast does not give that species any real right to a place in the British 

 fauna, so a northern form may in similar times of its abundance extend 

 southward, or a southern one northward. And of course to the casual 

 collector such occurences are most delusive. Indeed, no single record 

 of a species in any given locality is, I believe, sufficient to justify us 

 in assuming that such a locality marks the extent of its true specific 

 range, nothing but observations conducted consecutively over a long 

 series of years are really sufficient for such a conclusion, observations 

 which could determine whether the species was merely a chance 

 visitor impelled by some migratory instinct to diffuse itself, or 

 whether it was so far established as to appear in fewer or greater 

 numbers during most years and to be resident there during all stages 

 of its existence. 



These are some of the difficulties which beset an enquiry into a 

 subject as yet perhaps hardly ripe for discussion. Year by year, 



