300 



ME. A. B. WALLACE ON INDIAN ETC. 



having, as already pointed out, a decided relationship with the 

 Philippines, and also an apparent direct connexion with New 

 Guinea. It also possesses genera quite peculiar to itself, and 

 has an unusual number of endemic species. The Sulla Islands 

 closely agree with it, and are distinctly marked off from the 

 Moluccas, and must therefore form part of the " Celebes 

 group." The islands of Lombock, Sumbawa, Mores, and Timor, 

 with others adjacent, differ much in physical character from the 

 rest of the archipelago, and possess genera and species which 

 indicate a closer connexion with Australia. Their proximity 

 to Java has also led to their being partly populated with species 

 from that island ; and they altogether possess a distinctive cha- 

 racter which requires them to be considered apart. They form 

 the " Timor group." 



Although these groups and regions are exceedingly well marked 

 in Birds and Mammals, and must therefore be taken as the 

 foundation of any scheme of division of the islands according to 

 the distribution of their animal and vegetable productions, yet it 

 is undoubtedly the fact that in the great group of insects these 

 divisions are by no means so clearly marked. Insects have a much 

 more uniform distribution in these countries, as in fact we might 

 expect from the fact that they are much more liable to be acciden- 

 tally carried from island to island — in their egg- and larva-states 

 by floating trees, trunks, and fruits — in their perfect condition 

 by strong winds and hurricanes ; and as the climate and general 

 conditions of the surface vary very little from island to island, such 

 immigrants would, in many cases, survive and lay the foundation 

 of new races. In a paper " On some Anomalies of Zoological 

 and Botanical Geography " (Nat. Hist. Eeview, Jan. 1864), I 

 have explained my views on this subject at some length. 



In the summary of the distribution of the genera of the Acu- 

 leate Hymenoptera catalogued by Mr. Smith, I have separated 

 the Apterous Ants from the rest of the order, to see if they 

 would present any difference with regard to their distribution in 

 the two great regions. Out of 39 genera of ants 13, or exactly 

 one-third, are common to the two regions. Of the 123 genera of 

 winged Aculeate Hymenoptera, 69 genera, or more than half, are 

 common to the two regions. We may reasonably conclude, there- 

 fore, that it is the power of flight that has led to this average 

 wider extension of the winged groups. If, instead of comparing 

 the genera of the two halves of the archipelago, we compare the 



