8 R. W. CROSSKEY 
out of position in a permanent preparation so that an undistorted profile or apical 
view is not given. It is therefore vital to examine the hypopygium in fluid and to 
compare the shapes of the surstyli and cerci against the figures before slide mounting. 
All the accompanying figures of the male epandrium, surstyli and cerci have been 
drawn from whole hypopygia removed from the flies, slightly softened in potassium 
hydroxide solution, and mounted in fluid to show either the shape in profile (lateral 
view) or in apical view. Some of the specific differences in shapes of surstyli and 
cerci are very subtle, and to get comparable posterior views the hypopygium has 
always been orientated in such a way that the sclerotized dorsal part of the epan- 
drium is just visible above the ‘open’ membranous part. This should be kept in 
mind when comparing an apical view of the male hypopygium against the figures. 
As a rule it is not possible to obtain very satisfactory views of the male hypopygium 
by extracting it in situ on relaxed flies; some very important features lie at the 
bases of the surstyli and may be concealed under the epandrium and overlooked 
unless the hypopygium is completely removed, so that it can be viewed from various 
angles in fluid at least while an identification is being made. (Examination of the 
male hypopygium is only needed at the specific level, and as species do not normally 
show important characters on T5 or on sternite 5 it does not usually matter greatly 
if the surrounding parts of the abdomen are slightly damaged when the hypopygium 
is removed.) 
When describing the leg chaetotaxy the convention is followed of imagining the 
leg to be extended at right-angles to the longitudinal axis of the fly, when: ad = 
anterodorsal, av = anteroventral, pd = posterodorsal, and pv = posteroventral. 
The close-set comb of setulae on the hind tibia of many forms is referred to as the ad 
fringe, using the conventional positional terminology ‘ad’; this equates with Para- 
monov’s (1968) term ‘externodorsal’. 
The abbreviations used for thoracic chaetotaxy are: acr, acrostichal setae; dc, 
dorsocentral setae; za, intra-alar setae; ph, posthumeral setae; stpl, sternopleural 
setae. Position before or behind the transverse suture of the mesonotum is indicated 
by prst (presutural) and post (postsutural) respectively, in the normal convention; 
hence prst dc indicates presutural dorsocentral setae, post 1a indicates postsutural 
intra-alar setae. 
Abdominal tergites are indicated by the letter T followed by the appropriate 
number; the composite first apparent tergite is Tr + 2, the last visible tergite T5 
(Text-fig. 28). (It should be noted here that Paramonov (1968) referred to abdominal 
tergites by their apparent number, not by their correct numbering on the basis of 
morphological segmentation: his ‘first’ tergite is correctly Tx + 2, his ‘second’ and 
‘third’ tergites are T3 and T4, and his ‘fourth’ tergite is T5.) For the convenience 
of Australian workers the terminology of the parts of the male hypopygium is that 
adopted by Colless & McAlpine (1970) in their work on Australian Diptera. 
ADULT CHARACTERS AND THEIR TAXONOMIC VALUE 
At present only morphological characters of adult flies are available for classifica- 
tion and species recognition. The following account details the characters that 
