144 



DISTRIBUTION OP THE DIPTERA BRACHYCERA OP AUSTRALIA, 



Genera classified on records of distribution. — Various Australian entomolo- 

 gists are attempting to discover, amongst the families of insects tbey are study- 

 ing, genera that can be classified into one or more of the following groups: — 



1. Genera limited to Australia. 



2. Genera that have invaded Australia from the North. 



3. Genera that have a bearing upon the theory that Australia at one time 

 was connected with South America via the Antartic land. 



The table given below shows the possibility of being able to place certain 

 genera into these classes but any serious attempt to do so would be impaired in 

 value by the admitted incompleteness of our records. 



Table of percentages. — The Diptera Brachycera are represented by 156 

 genera known to me from Australia and this number includes some not previously 

 recorded and omits others inaccurately recorded from the region. 



Of these genera 33 (21%) are cosmopolitan and 73 (46.8%) are only known 

 from Australia. Other figures are given in the following table : — 





Number of the tabu- 

 lated genera oceur- 



Percentage of the 

 Australian genera 



Number of the tabu- 

 lated genera less the 



Percentage of the 

 Australian (exclud- 

 ing cosmopolitan 

 genera known from 

 other regions. 





ing 



in the seven 

 regions. 



known from other 

 regions. 



33 of cosmopolitan 

 distribution. 



N orth America . . 





54 



34.6 



21 



17.1 



South America . . 





68 



43.6 



35 



28.5 







156 



— 



123 



— 



Malayan and Poly- 













nesian Islands 





53 



33.9 



20 



16-3 



Amended figures 













for these islands 





(66) 



(42.2) 



(33) 



(26 S) 







52 



33.3 



19 



15.4 







46 



29.6 



13 



10.6 







40 



25.5 



7 



5.7 



Remarks. — In the table showing the dispersal of the genera there are several 

 cases where a genus is stranded in one or more regions and does not appear to 

 have a continuous distribution. In the course of time many of these will lie 

 joined by the discovery of species in the intermediate regions. Other genera 

 have similar distributions which are too incongruous to pass without remark. 



Krober, in his revisions on the Therevidae has recorded the genera TSetinor- 

 rhijnckns and Anabarrhynchns from Africa. Both these genera are typical of 

 the Australian and South American regions and it seems probable that the Afri- 

 can species placed in them do not strictly belong there. A study of Krober's 

 work, as far as the Australian material is concerned, has convinced me that in 

 many cases he has failed to appreciate certain characters of generic value and 

 on this account I feel certain that the African species placed by Krober in the 

 two genera referred to will ultimately be removed to some other position. 



The cosmopolitan genera include many that will be divided into more than 

 one genus when they are properly studied. This is especially the case with 

 genera containing long series of species such as Nieoitamus (used in a very wide 

 sense in the table) which is receiving attention at the present time. 



Some of the genera belonging to the Empidae and Dolichopodidae are only- 

 known from restricted areas and these will probably be found widely distributed 

 when more attention is given to them. Several genera belonging to the former 

 family are added to the Australian fauna for the first time in this list. 



In the Tabanidae the genus Dasi/basis is omitted from the numbers counted 

 as it has not been satisfactorily recognised during recent years. The occurrence 



