18 R. W. CROSSKEY 
These setae are weak or absent in many forms, and when present are usually 
only strong in females. They are present in females of Goniinae, but usually 
absent or represented by mere hairs in males (in the Siphonini both sexes have 
strong outer verticals). 
palpi. The paired forwardly directed appendages of the proboscis arising between 
the base of the mentum and the oral cavity. 
Presence or absence of palpi, and shape and size when present, often provide 
useful key characters. Palpi are usually present (virtually always in Goniinae) 
but may be totally absent as in Cylindromyia or vestigial (e.g. Linnaemya, 
Chaetophthalmus, some Stomatomyia). Exceptional development sometimes 
occurs in which the palpi project far beyond the epistomal margin (e.g. 
Exechopalpus) or are greatly swollen and clubbed (e.g. females of Rutzlotrixa). 
parafacials. The paired anteroventral areas of the head separating the eyes from 
the facial ridges and lying between the parafrontals and the genae (parafacialia, 
Wangen of Mesnil) (Text-figs 1 & 2). 
These areas are taxonomically important for their vestiture and breadth in 
relation to, for instance, the width of the face or the antennae. Most often 
the parafacials are bare, but they may be haired to a varying extent or may 
carry strong bristles. In many forms the descending rows of frontal setae 
reach down on to the upper parts of the parafacials, but these setae are discounted 
when the parafacials are described as bare (in descriptive practice the ‘parafacials’ 
normally means those parts of them lying ventrally to the lowermost frontal 
setae). 
parafrontals. The paired areas forming the outer parts of the frons and abutting 
against the eyes (orbits, fronto-orbital areas, parafrontalia) (Text-figs I & 2). 
Normally the parafrontals are separated from each other by the interfrontal 
area, but in some forms they meet each other in the mid-line of the frons and 
partially or wholly obliterate the interfrontal area. Usually when they meet 
the head is holoptic or nearly so, but a very few forms with very broad frons 
have parafrontals that not only meet in the mid line but have lost most or all 
of the line of union so that the entire frons is formed of completely coalesced 
parafrontals (e.g. males of most Heterometopia). Hairing of the parafrontals 
can be of minor taxonomic usefulness at specific level. 
peristome. The lower margin of the head around the buccal opening. 
The term is used by Mesnil for the whole of the area here termed the gena. 
peristomal setae. Lower marginal setae of the head standing on the peristome 
(Text-fig. 3). 
petiolate. Provided with a petiole (q.v.) (said of wing cell R;). 
petiole. The short length of wing vein formed by the union of the apices of veins 
R,,, and M, in wings in which cell R, is closed before the wing margin. See 
under cell R; above. 
pleurotergite. The convex area of the side of the thorax lying above the hind 
spiracle and between the pteropleuron and the mediotergite (sguamopleuron, 
supra-spiracular convexity). 
This area is bare (i.e. has only a nap of microscopic pubescence) in nearly all 
