12 RK. W. CROSSKEY 
discal setae. Setae standing medially or submedially on a specified surface (e.g. 
scutellum or abdominal tergites). 
Most often used with reference to strong erect setae standing centrally on 
one or more of the abdominal tergites (the 1/D of Townsend). 
distiphallus. The apical part of the aedeagus of the male genitalia (phallus, 
aedeagus, preputwum) (Text-figs 22 & 23). 
Of considerable taxonomic importance at various levels because of its diversity 
of form. Sometimes bizarrely developed in whip-like or coiled form. 
divaricate. Directed outwards from one another. 
Used in particular of the ocellar setae when these curve neither forwards 
(proclinate) nor backwards (reclinate) but curve outwards from each other 
towards the eyes (e.g. in Paragonia). 
dorsocentral setae. The two longitudinal rows of setae on the mesonotum outside 
of the acrostichal setae (presutural + postsutural setae of Townsend) (Text-fig. 4). 
Typically these are the strongest and most stable of the mesonotal setae 
(excluding the presutural seta and the first supra-alar), but are weak or variable 
in a few groups (notably Phasiini and Rutiliini). The number of dorsocentral 
setae forming the presutural and postsutural complement is of great taxonomic 
importance, particularly in the Goniinae. Many genera and tribes are completely 
constant in their dc complement (e.g. all Sturmiini have 3 + 4 dc setae). 
epandrium. The large curved plate of the male hypopygium that bears the cerci 
and surstyli and is morphologically the ninth tergite (TG/X) (Text-fig. 23). 
Apparently well developed in all Tachinidae but of limited taxonomic use 
except for slight modifications in its vestiture. 
epistomal axis. An imagined horizontal line through the head profile at the level 
of the epistomal margin (oval margin axis) (Text-fig. 14). i 
Head length at the epistomal axis in relation to length elsewhere (e.g. at the 
antennal axis) can be significant in describing head form. 
epistomal margin. The anteroventral edge of the epistome (oval margin). 
epistome. The lower anterior part of the head below the face and between the 
vibrissae (epistoma) (Text-figs 1, 2 & 12). 
The development of the epistome is taxonomically important. Often there 
is no epistome clearly differentiated from the face (e.g. Minthoini, Nemoraeini), 
but in many forms there is a strongly developed epistome which curves forwards 
from face and is easily visible in front of the vibrissal insertions when viewed 
in profile (e.g. in many Alophora, most Rutiliini, Chaetophthalmus). In the — 
Tachininae the presence of a prominently projecting epistome (visible in profile) 
or a flat epistome (invisible in profile) provides a very important key character 
separating groups of tribes. When the epistome is prominent its margin is 
usually well below the level of the vibrissal insertions, and when exceptionally 
pointed and projecting is usually referred to as subnasute. 
erect. Standing upright in relation to the surface (said of hair or setae to contrast 
their orientation with others that lie down) (cf. recumbent). 
excavate. With a depression (said of abdominal Tr + 2). 
The extent of the median dorsal depression of abdominal Tr + 2 is of great 

