54 DIPTERA OF AUSTRALIA, 



Russia to Italy ; from Egypt and the Cape of Good Hope ; from 

 North and South America, Borneo, and Australia ; and Lasioptera 

 is known to have nearly an equally wide range ; and I believe that 

 when the family has been equally studied in all countries, most if 

 not all the genera and subgenera will be found represented all over 

 the world ; and though many forms may yet be discovered 

 peculiar to certain countries, it is not probable that they will 

 very greatly differ from known examples. The small species 

 belonging to Heteropeza, 3fiast07\ and Gampi/lomyza, scai,rce\y visible 

 when on the wing, have been discovered in the widely-separated 

 continents of Europe and Australia, and the last of these also 

 from America ; so, doubtless, they exist in Africa and elsewhere. 

 A few species are common to America and Europe, but these 

 evidently have been conveyed through the medium of commerce 

 from one country to the other, through the introduction of the 

 food plant.* According to Prof. Hutton, Cecidomyidse ai'e 

 represented in New Zealand, but, like many of the other smaller 

 insect.s, have never yet been described from that country. Certain 

 it is, that the family is scattered far and wide over the whole 

 globe. Examples are to be found in quite different, indeed 

 opposite climates, with widely distinct floras, and therefore sup- 

 porting perfectly indigenous species of gall-gnats. Th'e sub-genera 

 Cecidoiiiyia and Epidosis are not only known to occur in widely 

 remote latitudes, but they have been also detected in amber, 

 which, although a fossil resin, is not regarded geologically as a 

 very ancient product. Cecidomyidse probably existed much earlier 

 — undoubted remains of numerous Diptera have Ijeeu found in 

 the well-known Stonetleld slate and lias of the Me.sozoic ages. The 

 apparently extinct genus Monodicrana has been established for a 

 species described by Prof. Loew in 1850 from amber, and found 

 associated with Cecidomijia and Epidosis. 



That the species of this family all originated from a common 

 centre, from a common stock, and since become widespread, is I 

 think indisputable, but our present knowledge is iusufiicient to 



* Since this paper was written, the Hessian tly has also been reported 

 as causing much damage in the Wellington district. New Zealand. 



