DISTRIBUTION OP INSECTS. 281 



An extended meridional extension is more frequently to be observed 

 among the tropicopolitan forms than among those which more 

 properly belong to the temperate regions ; and this is especially 

 the case among African insects, where frequently the same spe- 

 cies is found to inhabit both the northern and southern parts of 

 the continent. This condition is also to be observed in the case of 

 northern forms, when mountain-chains, trending in a meridional 

 direction, permit of easy access to regions of very varying physio- 

 graphical features, which in their more elevated parts present 

 conditions more nearly uniform with those exhibited elsewhere on 

 the lowlands. Thus, we find in the Chilian fauna numerous forms 

 that more properly belong to the north temperate zone the pre- 

 ponderating element among the Carabidso, for example, and the 

 genera Lycsena, Colias, and Argynnis among the butterflies. These 

 not improbably found their way southwards in successive migra- 

 tions along the Andean mountain-system, where suitable habita- 

 tions, corresponding in general physiographical features to those 

 of their northern home, could readily be found. A broad horizon- 

 tal or latitudinal distribution, per contra, characterises the insect 

 fauna of the north temperate zone. A large proportion of the 

 European species, for example, are spread over the far interior of 

 the Asiatic continent, and, indeed, many of them reappear in 

 America. Nothing more strikingly illustrates this broad diffusion 

 of species than the case of the Japanese lepidopterous fauna, which, 

 out of some 1,110 species of Macro-Lepidoptera, contains, accord- 

 ing to Pryer, 103 not less than 123 species that are common to Great 

 Britain, or about 16 per cent, of the entire British fauna. 



Some remarkable and not wholly comprehensible anomalies of 

 distribution are exhibited by the faunas of almost every region, 

 which render unusually intricate the general problems of distribu- 

 tion presented by the class as a whole. One of the most interest- 

 ing and instructive of these is the special relationship which unites 

 the New Zealand and Chilian and Patagonian coleopterous faunas, 

 and the distinctness of the fauna of the first-named region from the 

 Australian, 104 a condition which, as Professor Hutton has shown, 

 also characterises some of the other animal groups, and which 

 would seem to argue in favour of some former direct land connection 

 (trans-Pacific) between New Zealand and a portion of the South 

 American continent. 



