OF THE MALAYAN REGION. 29 
conspicuous in insects, but is shown in some degree by the Papilionidæ. . The following 
groups are either almost or entirely restricted to one portion of the Archipelago :— 
Indo- Malayan Region. Austro-Malayan Region. 
Noz-group. Priamus-group. 
Coon-group. Ulysses-group. 
Macareus-group (nearly). Erechtheus-group. 
Paradoxa-group. 
Dissimilis-group (nearly). 
Brookeanus-group. 
Leprocircus (genus). 
The remaining groups, which range over the whole archipelago, are, in many cases, 
insects of very powerful flight, or they frequent open places and the sea-beach, and are 
thus more likely to get blown from island to island. The fact that three such charac- 
teristic groups as those of Priamus, Ulysses, and Hrechtheus are strictly limited to the 
Australian region of the archipelago, while five other groups are with equal strictness 
confined to the Indian region, is a strong corroboration of that division which has been 
founded almost entirely on the distribution of Mammalia and Birds. 
If the various Malayan islands have undergone recent changes of level, and if any of 
them have been more closely united within the period of existing species than they are 
now, we may expect to find indications of such changes in community of species between 
islands now widely separated ; while those islands which have long remained isolated would 
have had time to acquire peculiar forms by a slow and natural process of modification, 
An examination of the relations of the species of the adjacent islands will thus enable 
us to correct opinions formed from a mere consideration of their relative positions. For 
example, looking at a map of the archipelago, it is almost impossible to avoid the idea 
that Java and Sumatra have been recently united ; their present proximity is so great, and 
they have such an obvious resemblance in their volcanic structure. Yet there can be 
little doubt that this opinion is erroneous, and that Sumatra has had a more recent and 
more intimate connexion with Borneo than it has had with Java. This is strikingly shown 
by the mammals of these islands—very few of the species of Java and Sumatra being 
identical, while a considerable number are common to Sumatra and Borneo. The birds 
show a somewhat similar relationship; and we shall find that the group of insects we are 
now treating of tells exactly the same tale. Thus :— 
Sumatra ..... DS | 20 sp. common to both islands ; 
BOM Gs -> 29 sp.j 
Sumatra ..... 21 sp. | 11 sp. common to both islands ; 
Jaa ws 27 sp. 
Borneo, . „sa 29 sp. 20 sp. common to both islands ; 
Jaya is Fe on 27 sp. 
showing that both Sumatra and Java have a much closer relationship to Borneo than 
they have each other—a most singular and interesting result when we consider the wide 
separation of Borneo from them both, and its very different structure. The evidence 
