114 R. W. CROSSKEY 
gastrina as a synonym of Chetogaster, and he maintained this synonymy in his later 
paper on the genus (Paramonov, 1968). Here it is considered that Paramonov was 
in error, for stolida shows scarcely any of the diagnostic characters of Chetogaster 
but—on the contrary—shows all the essential characters of Parampbolia (q.v.); 
the g sternite 5 and genitalia, taken with the haired suprasquamal ridge, multiple 
postalar setae, etc. show beyond doubt that the true affinities of stolida are with 
assinulis Macquart, the type-species of Paramphibolia, and Chaetogastrina is here 
placed as a synonym of Paramphibolia (see p. 100). 
In his earlier paper, Paramonov (1954) placed three species in Chetogaster which 
he later (Paramonov, 1968) removed to other genera: C. nigrithorax (Macquart) and 
C. wilsoni Paramonov he placed in his genus Ola Paramonov, 1968, and C. diversa 
Paramonov he placed in his genus Ruwya Paramonov, 1968. It is here agreed with 
Paramonov that nigrithorax, wilsoni and diversa do not belong in the genus Cheto- 
gaster; they are considered not to belong in the Rutiliini at all in the present defini- 
tion of the tribe and are therefore omitted from further consideration. 
The uncertainty over placement of these species is not surprising, for it is by no 
means certain that Chetogaster itself should really be included in the Rutiliini. 
Many of the characters of the genus fail to conform with those possessed by typical 
Rutiliines and the genus should perhaps be looked upon as annectant between the 
Rutiliini and the Prosenini. The narrow facial keel, robust form, haired propleuron, 
and number of postalar setae (two) and scutellar marginal setae (three pairs including 
the apicals) give the genus a facies reminiscent of the genus Billaea Robineau- 
Desvoidy from Eurasia and Africa, and Chetogaster seems to be an Australian coun- 
terpart to the African Billaea. The characters of Chetogaster certainly make it 
difficult to differentiate the Rutiliini from the Prosenini in a completely satisfactory 
way, but it nevertheless seems useful to maintain the two tribes in spite of the 
existence of some baffiing forms that are hard to place in either tribe with confidence. 
For the present I follow the traditional placement of Chetogaster and retain the genus 
in the Rutiliini, pending better evidence on the real affinities (at the present time 
nothing is known of the early stages and host-relations of Chetogaster). 
There is no practical difficulty in distinguishing Chetogaster from other genera 
within the Rutiliini as it differs from all of them by having only two setae on the 
postalar callus (the normal number in Tachinidae). An interesting feature of the 
genus, not found elsewhere in the Rutiliini, is the existence of sexual dimorphism 
in the palpi—those of the male being slender as in other Rutiliines, but those of the 
female being very conspicuously clubbed. Some Chetogaster species (three out of 
the seven currently recognized species: see key) possess a small tuft of short fine 
hairs on the upper part of the mediotergite just below the base of the lower calypter, 
and this, too, is of unusual interest: such infrasquamal setulae (as they are usually 
termed) occur in a number of unrelated Tachinidae, but are of very rare occurrence 
in the whole subfamily Proseninae and occur in no other Rutiliini. 
The male genitalia and sternite 5 of Chetogaster species shed no light on the affini- 
ties within the Proseninae. The aedeagus is exactly similar to that of other 
Rutiliini (though the membranous and the sclerotized parts of the distiphallus are 
perhaps slightly longer than in most Rutiliines) and the surstyli and cerci show no 
