NOTES ON LUFFIAS. 149 



the effect of such a general submergence during or after the glacial 

 epoch as the shell beds of Moel Tryfoen and Macclesfield were at one 

 time held as indicating, there is little doubt but that we might 

 consider the ropeopling of these islands after the passing away of 

 glacial conditions and their re-emergence above the waters as dc novo. 

 But I believe such views as these have been to some extent modified 

 of late years, the great or at any rate total submergence seems not 

 beyond a doubt, and some biologists maintain that the severity of the 

 glacial age has been greatly overstated and that the bulk of our flora 

 and fauna might easily have survived its influence. Possibly such 

 opinions are less frequently advanced by those who have approached 

 the subject from the geological side. It is impossible for any biologist 

 to quite explain away the glacial age in Britain. The climatic 

 conditions of which we have the most indisputable evidence did obtain 

 at some period, must have very greatly modified our Hora and fauna 

 if they did not destroy them. Even in a climate as mild as northern 

 Norway is now, the majority of our present insects could not have 

 existed, and, consequently, if they existed here previously, must have 

 been destroyed and subsequently reintroduced on the passing away of 

 such conditions. 



It is not my purpose, however, here, to reason from geological data 

 to insect derivation, but rather to examine what data we have of 

 insect or rather coleopterous distribution, and attempt from them the 

 construction of any theories of derivation, which of course will 

 involve geological considerations also, and we shall, I think, see from 

 such an examination, that while the little evidence it affords lends no 

 support to the idea of a complete glacial extinction and subsequent 

 continental diffusion of all present forms, still less does it admit of 

 explanation by any theory of continuity of all of them here since 

 pleiocene days. 



{To he coiitiiiued.) 



Notes on Luffias— with incidental remarks on tiie phenomenon of 



parthenogenesis. 



By T. A. CHAPMAN, M.D., F.Z.S., F.E.S. 

 lyCoiiti nurd from p. 95.) 



A most interesting point in this genus is the parthenogenetic cha- 

 racter of Liiffia fcrcJntiilti-lla. Parthenogenesis occurs in various orders 

 of insects, and presents several forms. In Aphides it is associated 

 with an alternation of generations, and has been the subject of exten- 

 sive observations by eminent biologists. It would appear that it does 

 not occur in any other insects in precisely the form in which we find 

 it in Aphides. In these there is a long succession of generations 

 parthenogenetically, ending in an ordinary sexual form ; the partheno- 

 genetic individuals are not, however, ordinary females, i.r., they have 

 not only no relation to any actual males, but they have no possible 

 relations with any imaginable males, that being so, it is not irrational 

 to assert, as has been done, that these are not, in fact, females. The 

 cycle is generally an annual one, the sexual forms being produced in 

 view of the necessity of migration either to other food-plants or to 

 make provision for hybernation. The parthenogentic forms are 

 always wingless. In the origin of these two now correlated characters, 



