12 R. 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 MD of Townsend). 



distiphallus. The apical part of the aedeagus of the male genitalia (phallus, 

 aedeagus, preputium) (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 (TGIX) (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 (oral margin axis) (Text-fig. 14). 



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 (oral 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 Ti + 2) . 



The extent of the median dorsal depression of abdominal Ti + 2 is of great 



