188 AUSTRALIAN FLIES OF THE FAMILY ASILIDAE, 



row on the anterior side, one subapical spine on the posterior side, and a ventral 

 i-ow. The row on the anterior side niaj' vary in the number of spines, and may 

 even be reduced to one or two ; this row often runs on to the dorsum, and, in !-uch 

 a case, if the last spine is isolated with a bare space between it and the other re- 

 maining spines, it will appear to be a subapical dorsal spine. 



A complement of spines on the posterior femui- consists of two rows on the 

 anterior side and one ventral row. Besides these there are a few suba]iical 

 spines . 



In a long series of specimens a wide range of variation will geueraliy be 

 found, but in a few species the variation is limited. 



Wings. The wings are hyaline, or more or less tinted with fuscous, and 

 fuscous spots are present in a few species. The venation is constant with regard 

 to the veins and cells, but slight variations occur in the relative '5hape and length 

 of some of the cells. 



Male genitalia. The exposed genital forceps of the male aft'ord the only 

 satisfactory characters for identifying a species. This organ lias a wonderful 

 variety of characters that have been all but overlooked by earlier authors, and 

 it is the purpose of the present paper to utilise them as the main objective for 

 establishing species. The females in such a system of classification are, neces- 

 sarily, of secondary consideration ; nevertheless, thej' can generally be identified 

 by other characters by comparison with their respective males. 



The male genitalia contain a pair of upper forcepa, between the two branches 

 of which is situated the dorsal msdian lamella, and a pair of lower forceps — in 

 all, five visible parts 



The upper forceps vary considerably in shape in the various species, and 

 may contain a terminal process, or may be simple and without a process, and, 

 finally, may contain bristles. 



The genitalia of ^i. exilis ^Macquart, il. filiferus Maccjuart and Cerdistus 

 australis Ricardo are described as having bristles. 



Female ovipositor. Few descriptions convey any real idea of the length of 

 the ovipositor, yet sometimes females of closely related species can be separated 

 by the comparative length of this organ. White refers to the ovipositor as being 

 long in all his species except .Y. abditiw;, where, he states in the original descrip- 

 tion, it is rather short, and in 1917 he refers to it as unusually short. This 

 species, however, has a very distinctive ovipositor, and, on the strength of this 

 organ, it should be placed in a separate genus; it is somewhat compressed ven- 

 trally, but has a conspicuous dorsal surface which decreases posteriorly, and at 

 the apex there is a pair of small, separated, conical lamellae. All the other 

 species in the collection contain one, more or less cylindrical, stylilorm lam- 

 ella at the apex of the eighth abdominal segment which is usually entirely com- 

 pressed. Sometimes the seventh abdominal segment is black, shining, and com- 

 pressed on the dorsal surface, but shows a ventral area ; this character is called 

 subcompressed in the descriptions given below. In two species, one described 

 below as new, the sixth abdominal segment is also black, shining and subcom- 

 pressed . 



Both White and ]\Iiss Eicardo refer to those subcompressed segments as 

 forming part of the female ovipositor, but as gradations in the various species 

 make the line of demarcation difficult to determine, it is not advisable to interpret 

 the character in that manner. 



