14 R. W. CROSSKEY 
Palpostomatini or in both sexes of many Phasiini). The frons is of equal width 
in both sexes in all Siphonini and many Phasiinae, but rarely in other groups. 
frontal setae. The setae of the paired rows of setae standing on the inner edges 
of the parafrontals (Stivnborsten of Mesnil) (Text-fig. 3). 
These setae are strongly or moderately developed in most Tachinidae but 
may be weak and hair-like in Rutiliini and Phasiini and occasionally in other 
groups. The rows may be partially obliterated in forms with holoptic or 
semi-holoptic heads. Normally the setae of each row are directed inwards so 
they cross medially (cruciate frontals), but in a few forms some or all of the 
frontal setae are directed upwards and backwards (reclinate frontals). In 
Phasiinae and Proseninae the rows of frontal setae extend downwards only to 
the level of the antennal base or but slightly beyond, but in most Tachininae 
and Goniinae the rows reach downwards at least to the level of the middle of 
the second antennal segment and often beyond (in the latter case the rows 
extend well down on the parafacials where, particularly in males, they may be 
irregularly doubled, e.g. in Voriella). 
gena. The lateroventral part of the head between the bottom of the eye and 
the peristome or oral cavity (cheek, jowl, peristom of Mesnil) (Text-fig. 1). 
The depth of the gena from the lowest point of the eye to the ventral margin 
of the head when seen in profile can provide an important character, especially 
its proportion in relation to eye height or width of the profrons (e.g. much narrower 
in Carceliini than in other tribes of Goniinae). 
genal dilation. The swollen haired part of the gena continuous with the postbuccae 
and occiput (Occipitale Erweiterung auf dem Peristom of Mesnil) (Text-fig. 2). 
Commonly the genal dilation occupies most of the gena and reaches well 
forwards towards the vibrissal angles, but in some forms is reduced or virtually 
absent (in which case the gena is bare or mainly so). The genal dilation is 
normally extensively haired and sometimes bears a few stronger setae. 
hair fascicles. Dense, often convergent, tufts of hair on the abdominal venter. 
These are a secondary sexual character of males and occur mainly in a few 
genera of Goniinae. When present they are normally restricted to the venter 
or sides and venter of the fourth tergite (e.g. Palexorista) or of the fifth tergite 
(e.g. Paropsivora, Zosteromeigenia), but occasionally are present on two successive 
tergites. 
humeral calli. The paired convexities forming the anterolateral corners of the 
thoracic dorsum (humeri, posterior pronota, shoulders) (Text-fig. 4). 
humeral setae. The setae standing on the humeral calli (Text-fig. 4). 
The number and arrangement of these setae, particularly whether the main 
ones stand in a straight line across the callus or in a triangle, is taxonomically 
important at several levels. Usually each callus bears at least two differentiated 
humeral setae, but there may be only one or even no clearly differentiated seta 
(e.g. in Phasiini). 
infrasquamal hairs. A group of minute hairs or setulae on the mediotergite 
adjacent to the base of the lower calypter (Text-fig. 7). 
Presence or absence of these hairs is sometimes a useful minor taxonomic 
