TACHINIDAE OF AUSTRALIA 25 
These are normally two, one behind the other, with the anterior one very 
strong. The anterior one is, with the presutural seta, one of the most stable 
and universally present setae in the tachinid chaetotaxy. Sometimes one or 
two supernumerary supra-alars may be developed in addition to the normal 
two, or the posterior supra-alar may be absent or hair-like. The second or 
posterior sa seta is always present in Goniinae but is absent in such tribes as 
the Phasiini and Palpostomatini and often in Ormiini. 
Some authors consider the pre-alar seta (pra) as the first of the supra-alar 
setae and number the others accordingly (e.g. the posterior supra-alar is then 
the third supra-alar), but this is an undesirably confusing terminology. When 
both the pre-alar and the posterior supra-alar are absent (as in Phasiini and 
Palpostomatini) the anterior supra-alar is the only seta present on the supra-alar 
area and therefore stands very conspicuous and isolated. 
suprasquamal ridge. The weakly sclerotized area at the base of the postalar 
wall to which the lower calypter is attached marginally (tympanic ridge of 
Townsend) (Text-fig. 7). 
This structure is taxonomically useful according to whether it is bare or 
haired. The suprasquamal ridge is bare in all Phasiinae and Goniinae, and 
in the Proseninae hairing is confined to the Rutiliine genera Rutilia, Amphibolia 
and Chrysopasta; the ridge is apparently bare in all Tachininae except Servillia 
jakovlewti (Portschinsky). 
surstyli. The outer pair of articulated processes attached to the epandrium of 
the male hypopygium (paralobes, outer forceps, tenth sternite lobes of Townsend) 
(Text-figs 21 & 23). 
The form of the surstyli is of great taxonomic value at specific level but they 
have relatively little taxonomic use at higher levels. 
tegula. The small anterior sclerite at the exteme base of the wing before the 
basicosta (epaulet). 
tergites. The main segmental plates of the abdomen forming almost the entire 
circumference of each segment. 
The tergites are taxonomically important in so far as their individual and 
collective forms give shape to the abdomen and determine, for example, whether 
it is elongate subcylindrical as in Cylindromyia and Doleschalla, or rather broad 
and flattened as in many Phasiini and Rutiliini, or subovate as in the majority 
of forms. In the Goniinae the ventral ends of the tergites meet in the mid- 
line of the abdomen, but in many forms in the other subfamilies they do 
not meet each other and the sternites are then exposed. Lengths of the 
tergites relative to each other, special modifications such as the depression of 
T5 found in many Rutiliini or the keel-like form of the abdominal venter in 
some Blondeliini, and pollinosity and pattern on the tergites can all provide 
useful characters. 
third costal sector. That sector of the costa lying between the apices of veins 
kK, and R, . 5. 
_ transverse suture. An impressed line across the mesonotum dividing it into 
anterior and posterior parts (prescutum and scutum, q.v.) (Text-figs 4 & 7). 
