CHAP. XXL] INSECTS. 485 



sub-region which never cross the narrow seas to the east of 

 them ; 6 others which only pass to Celebes ; and 2 more which 

 have extended from Java along the closely connected line of 

 islands eastwards to Timor. On the other side, we find 5 strictly 

 Austro-Malayan genera, and 2 others which have a single re- 

 presentative in Java. The following is a list of these genera : 



INDO-MALAYAN GENERA : Amathusia, Thaumantis, Tancecia, 

 Eurytela, Ilerda, Zemeros, Taxila, Aphneus, Prioneris, Dercas, 

 Clerome, Adolias, Apatura, Limenitis, lolaus, Leptocircus, (the 

 last six reach Celebes) ; Discophora, Thestias ; (the last two reach 

 Timor.) 



AUSTRO-MALAYAN GENERA: Hamadryas, Hypocista, Mynes, 

 Dicallaneura, Elodina, Hyades, Prothoe (the last two reach 

 Java). 



The most characteristic groups, which range over the whole 

 Archipelago and give it a homogeneous character, are the various 

 genera of Danaidae, the genus Elymnias, and Amblypodia with a 

 few other Lycaenidae. These are all abundant and conspicuous 

 groups, but they are nevertheless exceptions to the general rule 

 of limitation to one or other of the regions. The cause of this 

 phenomenon is probably to be found in the limitation of the larvae 

 of many Lepidoptera to definite species, genera, and families 'of 

 plants ; and we shall perhaps find, when the subject is carefully 

 investigated, that the groups which range over the whole Archi- 

 pelago feed on genera of plants which have an equally wide range, 

 while those which are limited to one region or the other, have food- 

 plants belonging to genera which are similarly limited. It is 

 known that the vegetation of the two regions differs largely in a 

 botanical sense, although its general aspect is almost identical ; 

 and this may be the reason why the proportion of wide-ranging 

 genera is greater among such insects as feed upon dead wood, 

 than among those which derive their support from the juices of 

 the living foliage. This subject will be again discussed under 

 the various families of Coleoptera, and it will be well to bear in 

 mind the striking facts of generic limitation which have been 

 here brought forward. 



