22 THE entomologist's record. 



the mainland of Scotland. Nor in a geological sense is that period at 

 all remote, but quite recent, that is in Pleistocene times; there is, indeed, 

 general agreement that during this epoch, and subsequent to the maxi- 

 mum severity of the Glacial Period, there was such a general land eleva- 

 tion that Great Britain, Ireland, and all their surrounding islands formed 

 but one continuous extension of North-Western Europe. How far 

 this land area extended into what is now the North Atlantic 

 Ocean is, I believe, still uncertain, but it seems probable that such an 

 elevation must have continued for a long time, and through ver}' con- 

 siderable secular changes of climate. Daring its existence many 

 beetles may have reached what is now Tiree, difiering faunas may have 

 inhabited that area — diti'ering as the climate gradually from one age 

 to another altered, what we find there now are perhaps the final 

 survivors — a few, relics of the fauna of a colder age — a larger number, 

 those robuster forms which have persisted through all vicissitudes of 

 climate, unaffected as the Hebrides, severed from the mainland, sunk 

 deeper and deeper into the sea. and became a group of scattered islands 

 changed in climate, changed in flora, changed in most of the conditions 

 which we suppose affect insect life. For although, as I have suggested, 

 the majority of these islanders may have migrated into Tiree on the 

 wing in quite recent times, it is not necessary to suppose that they 

 must have done so. My own belief is that although the island stock 

 may have been replenished by air-borne recruits from the mainland 

 on various occasions, that essentially they have occupied Tiree, as the 

 Carabi must have done, from the beginning of its insularity. 



But a closer scrutiny of Mr. Donisthorpe's list reveals a few species 

 which can hardly be called dominant, as they are by no means 

 generally abundant, nor can they be classed with the Keltic group 

 since they are equally or even more frequent in the south than in the 

 north. They are, in fact, instances of that perplexing discontinuity 

 of range, which, in the present state of our ignorance, baffles all 

 attempts at elucidating their derivation. One of these is Paraci/imis 

 niii)-(>aenei(s, a beetle very restricted in habitat, occurring fairly 

 frequently in the south of England, very occasionally in the extreme 

 west of Ireland and Scotland, and in Man. The only conjecture one 

 can hazard about it is that it may have formed part of that group in 

 our insect fauna whose advent was probably from some past land 

 extension to the south-west of our present islands. Then there are 

 such species as Anchomejius piceus, Blethisa nmlHpunctata, Alcochara 

 hrevipentds, Bledius lonijulns, and perhaps one or two others, species 

 again strictly limited as regards habitat, and which occur sporadically, 

 but by no means commonly, over the entire Kingdom. 



Finally there remain a few cases which I think we might attribute 

 to the specializing efl'ect of insularity — a factor which possibly explains 

 some of the peculiar forms noted from Lundy and the Scilly Islands — 

 for it is obvious that the more circumscribed the area the less chance 

 would there be of any particular variation, arising how it might, from 

 becoming obliterated by free crossing with normal forms. Such is 

 the var. hinotattim, Steph., of Cercyon littoralis, which has also occurred 

 on the Irish coasts, the var, conjiuena, Donis., the only form of 

 Coccinella 11-punctata seen in the Island, and possibly also a very 

 singular brachypterous form of the common Xantlwlinus linearis which 

 cannot quite be matched by any mainland specimen that I have seen. 



