500 GEOGRAPHICAL ZOOLOGY. [PART iv. 



with a preponderance of Lamiidse ; and New Zealand 12, of which 

 the Cerambycidse are only slightly in excess. 



The relations between the Longicorn fauna of the several 

 regions, are such as are in accordance with the dependence of the 

 group on a warm climate and abundant vegetation ; and indicate 

 the efficiency of deserts and oceans as barriers to their migration. 

 The Neotropical and Australian regions have only 4 genera in 

 common, but these are sufficient to show, that there must proba- 

 bly once have been some means of communication between the 

 two regions, better adapted to these insects than any they now 

 possess. The Nearctic and Neotropical regions have 5, and- the 

 Nearctic and Palsearctic 13 genera in common and peculiar to 

 them, the latter fact being the most remarkable, because no 

 means of inter-communication now exists, except in high lati- 

 tudes where the species of the Longicorns are very few. The 

 Oriental and Australian regions, on the other hand, are closely 

 connected, by having no less than 52 genera of Longicorns in 

 common and peculiar to them. Most of these are specially 

 characteristic of the Malay Archipelago, often extending over all 

 the islands from Sumatra to New Guinea. This large number of 

 wide-spread genera of course gives a character of uniformity to 

 the entire area over which they extend ; and, with analogous facts 

 occurring in other families, has led many entomologists to reject 

 that division of the Archipelago between the Australian and 

 Oriental regions, which has been so overwhelmingly demon- 

 strated to be the natural one in the case of the higher animals. 

 The general considerations already advanced in Chapter II. 

 enable us, however, to explain such anomalies as this, by the 

 great facilities that exist for the transfer from island to island 

 of such small animals, so closely connected with woody vege- 

 tation in every stage of their existence. That this is the true 

 and sufficient explanation, is rendered clear by certain additional 

 facts, which those who object to the sharp division of the Indo- 

 Malay and Austro-Malay sub-regions have overlooked. 



An analysis of all the Malay Longicorns proves, that besides the 

 52 genera characteristic of the Archipelago as a whole, there are 

 100 genera which are confined to one or other of its component 



