143 



THE GEOGRAPHICAL DISTRIBUTION OF GENERA BELONGING TO 

 THE DIPTERA BRACHYCERA OF AUSTRALIA. 



By G. H. Hardy. 



Introduction. — The Diptera Brachycera have been sufficiently studied to make 

 it practicable to tabulate the range of the Australian genera. The main portion 

 of this tabulation is based upon the study of Australian species of Diptera which 

 arc sorted as far as possible into their genera and to this are added records from 

 works dealings witli these genera from other parts of the world. 



The compiled portion of tins paper is based upon the work of many en- 

 tomologists, some of whom are publishing results of their studies upon the Dip- 

 tera Brachycera within circumscribed areas whilst others are limiting their re- 

 searches to certain families of this group, but, however, covering a wider dis- 

 tribution. 



The usefulness of these works depends upon the accuracy of the records and 

 the manner in which the subject matter is presented. In many cases there is 

 much to be desired in these respects as some authors are content to let the identi- 

 fication of genera rest upon characters of rather doubtful generic value and do 

 not attempt to write a satisfactory definition covering the species known to 

 them. 



The task of describing new species and at best giving keys to the genera is 

 so palpably easy that the advanced work of defining genera is too frequently 

 ignored with the result that the original and often unsatisfactory definitions are 

 too much relied upon for the best results to be obtained. 



Nevertheless there appears to be a considerable uniformity in the under- 

 standing of genera of the Diptera Brachycera and it seems worth while to tabu- 

 late the distribution even in the present incomplete state of our knowledge. 



Amendments. — A striking weakness in our knowledge of the insect fauna 

 of those islands lying between Australia and the mainland of Asia, and the is- 

 lands in the Pacific (referred to here as the Malayan and Polynesian Islands), is 

 emphasised by the gaps filled with dotted lines in the tabulation below. The 

 genera with their distribution so marked undoubtedly occur in this region but 

 species belonging to them have not been described or reported from there. 



To overcome the slender knowledge of the Malayan and Polynesian diptera, 

 an amended set of figures is given in brackets and is obtained by including the 

 dotted lines when counting the number of genera known from the region. Although 

 the table of percentages is improved in this manner it will be noted that the 

 amended numbers are lower than those of South America from where the 

 known dipterous fauna is also limited. 



Undoubtedly various genera known only from Australia will yet be found 

 either in the Malayan and Polynesian Islands or in South America; and vice 

 versa, some of the genera only known from these regions will yet be found in 

 Australia. 



