84 C. H. Osten Sacken: Diptera 



it my duty to describe as new, every specimen that I could not 

 determine. A peculiar diflFiculty, attending the study of the diptera 

 in the large groups of islands of South Eastern Asia, consists in the 

 local varieties, which seem to exist on different islands. In several 

 instances I have been in doubt, whether to regard them as distinct 

 species, er as mere varieties; (for instance Rosapha habilis Wk. and 

 R. bicolor Bigot; the specimens of Chrysopila ferruginosa Wied. with 

 brown incisures on the abdomen, and those without them etc.). Such 

 questions will be easier to solve in a special monograph, based upon 

 more abundant materials. 



Incidentally, I have inserted general observations on genera, groups 

 and families, vs^hich I thought might be useful to the future worker in 

 the same direction. The synoptic tables which I give, will save him 

 some labor, but must be used with caution, as they have of necessity 

 been prepared either from notes, taken in different coUections, or merely 

 from descriptions. 



It would be prämature to found, upon such small materials, a final 

 opinion on the relation of the dipterous fauna of the Philippine Islands 

 to that of the Malay Archipelago. Thus much is evident, that the 

 relationship is consideräble. Both faunas agree in the large representation 

 of certain groups of diptera (for instance the genera Laphria, Promachus, 

 Ommatius, Milesia, the family Ortalidae), as well as in the scanty 

 representation of other groups (the Dasypogonina , with the exception 

 of a few genera, like Leptogaster and Damalis; the whole family 

 Bombylidae). Species widespread over South-Eastern Asia, occur here 

 also (Chrysops dispar, Chrysopila ferruginea, Psilophus vittatus, Syrphus 

 aegrotus, Eristalis errans, Ochromyia ferruginea, several Luciliae, 

 Scholastes cinctus, Nerius fuscus etc.). Several forms of an apparently 

 more restricted area are common to the Islands and to Amboina (the 

 genera Scamboneura and Damalina) , to Celebes (the genera Rosapha, 

 Telostylus; the species Sphyracephala cothurnata, Diopsis subnotata, 

 Tabanus v. d. Wulpi etc.). 



The claim of a fauna to individuality, the degree of its specialization, 

 are more difficult to define, upon such meagre data, than its relationship 

 to another fauna. In the präsent case, the relationship shows itself 

 principally in a similar distribution of groups ; whether the specialization, 

 when better investigated , will assert itself in a large proportion of 

 peculiar species, remains to be seen. In the vertebrata, the specialization 

 of the fauna of the Philippines is very remarkable. According to 

 Mr. A, R. Wallace (Island Life, p. 361) about nine-tenths of the 

 mammalia and two-thirds of the land-birds are peculiar species. 

 Such data led Mr. Wallace to believe 



