20 R. W. CROSSKEY 
In most Tachinidae the hind coxae are rather close to the abdominal base 
and the posteroventral declivity of the thorax consists of a median membranous 
area flanked by curved sclerotized areas (the metapleura). In a few forms 
(e.g. Cylindromyia, Doleschalla) the abdomen and the metacoxae are much 
more remote from each other than is usual and the entire posteroventral 
declivity of the thorax forms a fully sclerotized bridge between them; this forms 
an important taxonomic and key character. 
posthumeral setae. One or more setae standing anterolaterally on the prescutum 
immediately behind the humeral callus (Text-fig. 4). 
Development of these setae is rather variable and their taxonomic usefulness 
very limited. The pf setae are usually most strongly developed in Goniinae, 
in which two moderately strong posthumerals are normally present on each 
side, and least strongly represented in Phasiinae and Proseninae in which they 
may be absent or hair-like. 
postocular row. The regular row of setulae or long hairs on the upper and outer 
edges of the occiput immediately behind the eyes (Text-fig. 3). 
postorbits. The narrow laterodorsal strips of the head lying between the eyes 
and the postocular rows (Text-fig. 1). 
postscutellum. The transverse swollen lobe below the scutellum and dorsal to 
the mediotergite (subscutellum, infrascutellum, postnotum) (Text-fig. 7). 
This is almost universally present in Tachinidae and strongly convex. It 
is very weakly developed in a few forms (e.g. Palpostomatini) and is strongly 
produced backwards, squared and flattened in some Phasiini (e.g. Campbellia, 
Alophora subg. Mormonomyia). The postscutellum is always bare. 
postsutural. Behind the transverse suture of the mesonotum. 
pre-alar seta. A seta standing at the extreme anterolateral corner of the scutum 
anterior to, and approximately in line with, the supra-alar setae (first swpra-alar 
seta of authors) (Text-fig. 4). 
This seta is of the very greatest importance in tachinid taxonomy because 
of its variability in size, and, to a lesser extent, because of its presence or absence. 
The seta is universally present in the Goniinae (though it may be very weak) 
and may be either small (shorter than the first post ia seta or at most subequal 
to it) or very large (longer and stronger than the first post ia seta and usually 
also longer than the first post dc seta), and this distinction holds true almost 
without exception for the differentiation of two groups of Goniine tribes. In 
Phasiinae, Proseninae and most Tachininae the pre-alar seta is of the small 
type, and is sometimes absent (e.g. in Phasiini, some Minthoini and sometimes 
haphazardly in Proseninae). 
preapical (discal) scutellar setae. A pair or more of recumbent or semi- 
recumbent setae standing on the scutellum in advance of the marginal setae 
(Text-fig. 5). 
prescutum. That part of the mesonotum lying anterior to the transverse suture 
(Text-figs 4 & 7). 
Morphologically this is the anterior part of a divided scutum but the term 
