DEEIVATION OF BBITISH COLEOPTEEA. 183 



generally regarded as discontinuity of occurrence should be 

 more correctly attributed to discontinuity of appearance. 



Consider, for instance, such a case as Aegialia rufa, a 

 small Lamellicorn Beetle supposed to be peculiar to the 

 littoral of Lancashire and Cheshire in this country. Now, 

 within say the last thirty years, this district, that is, the 

 coast sandhills from Southport to Crosby and from 

 Wallasey to Hoylake has been, perhaps, as well searched 

 year by year by entomologists as any other of equal extent 

 in the kingdom, and this perplexing insect has during 

 three or four summers of this period appeared in profusion. 

 On those occasions it has, of course, been discovered and 

 recorded for this district only. This, on the face of it, 

 supplies an amazing instance of discontinuity of distri- 

 bution ; but if the sandhills all round the coast had been as 

 persistently searched as those of Lancashire and Cheshire, 

 is it unimaginable that Aegialia rufa might, in its years 

 of plenty, have been taken in many other localities ; in 

 fact, wherever round these coasts a suitable habitat offered 

 itself? You observe that, in this case, the Coleopterist 

 might have searched the Crosby and Wallasey sandhills 

 seven or eight years in succession, and declared as the 

 result of his investigation that Aegialia rufa did not occur 

 in that district. Another observer goes there the next 

 season and finds the insect one of the most abundant of 

 the fauna. 



You will gather from this that the study of the distribu- 

 tion of our insect fauna is beset with peculiar difficulties, 

 and that only close and systematic observation, extending 

 over a long course of years, is sufficient to justify the 

 assumption of the non-occurrence of many species in any 

 particular locality. This is just what we have not got. I 

 doubt if there be fifty Coleopterists in the whole of the 

 British Islands who systematically record the occurrences 



