176 THE entomologist's record. 



and diffusion of insect life in all its stages, the vast quantities of 

 timber, corn, fruit, hay, dye-woods, esparto grass, and various other com- 

 modities which daily reach these shores from all the ends of the earth, 

 as well as from just across the narrow seas, and the modern rapidity 

 of their transit, it seems absolutely certain that the opportunity must 

 be afforded to hundreds of species of establishing themselves here if 

 they were capable of it. It seems, however, probable that the land 

 connection between Britain and the continent existed sufficiently long 

 to allow of every species which could do so, and whose range was 

 sufficiently north-western, to extend themselves here, that the area 

 was in fact peopled to the full extent of its capabilities before severance, 

 and that there is now no room, especially since that area has been so 

 greatly modified by human agencies, no possible interstice into which 

 a newcomer can successfully thrust itself. No doubt, just as when the 

 whole area was continental, a favourable season or succession of seasons 

 might have enabled species to temporarily extend their range north- 

 ward, so now such conditions may allow a species to gain a provisional 

 foothold in these islands, but the average climatic conditions being 

 adverse, such species are always doomed sooner or later to extirpation, 

 and the result is that, although we continually meet with stray immi- 

 grants and even the descendants of such immigrants, still we are 

 pretty safe in assuming that, with the doubtful exception of a few 

 Longicornia or Scolytidae we have no coleoptera which, introduced by 

 other than natural means, that is immigration long before the epoch of 

 human civilisation, have permanently established themselves here. 

 Thus I hold that when a new species of Tachi/s, Tnii/ophlocus, or 

 Acupalpm, is discovered, we have no right, simply because the species 

 has not been recorded as British previously, or because its range seems 

 remarkably restricted, to immediately assume it to be an " introduc- 

 tion," on the contrary, I believe that, however limited or discontinuous 

 in range an insect may be, the fact that it is established at all is evidence 

 that its presence is not due to human introduction, but that it is 

 genuinely indigenous, and probably by reason of its limited range or 

 small size previously overloooked. But, on the other hand, the case is 

 quite different when we consider those numerous beetles whose 

 economy has been entirely modified by their contact with Homo sctjiiens, 

 which are quasi-domesticated, and follow mankind in all its wanderings 

 as faithfully as the inquiline bee does its host. I refer to such species 

 as those of the genera CarpopJtilas, Nausibius, 'rribolinw, Blaps, 

 TniieuoijeniKs, Meziiim, and many others will readily occur to the 

 coleopterist. Possibly the ancestors of such species may have lived at 

 some time under strictly natural conditions, but it is also probable 

 that some i'alandra played havoc with the stores of millet of the Swiss 

 lake dwellers, and that in the cave dwellings of the lost Dordogne some 

 species of Blaps was the obscure companion of pahpoiithic man. 

 However, as we may, I think, neglect accidental introductions in our 

 list of established coleoptera living under natural conditions, so we 

 must eliminate from our enquiry all those species which, although 

 undoubtedly well-established, live under more or less non-natural 

 conditions and depend for their continued existence on an environment 

 caused by human agency. 



There remains, of course, the great bulk of our fauna, these 

 we must now consider a little more critically ; and a very brief 



