TACHINIDAE OF AUSTRALIA 57 



Austra. sept' and 'N.G. [=new genus] ad Oestrophasia N. Holl.', and Brauer & 

 Bergenstamm's determination label that reads 'prosopina det. B. B.' (specific name 

 handwritten, remainder printed). 



Tribe ORMIINI 



This small tribe occurs mainly in the tropical and subtropical parts of the world, 

 and contains some of the most aberrant forms to be found in the Tachinidae. 

 Several genera have the chaetotaxy very reduced and have a robust form and curious 

 head facies reminiscent of the Oestroidea. Biologically the group is particularly 

 interesting because the first-stage larva is the most perfectly formed planidium 

 occurring in the Diptera (though Glaurocara has a similar planidium: see under 

 Glaurocarini) and the hosts appear always to be nocturnally active Orthoptera 

 (crickets and Tettigoniidae s.L). Many forms have the pallid coloration often 

 associated with nocturnally active flics. 



At present the Ormiini are uniquely characterized by having the prosternal 

 region of the thorax greatly inflated (usually more so in females than males) and 

 visible when the fly is seen in profile. The function of this oddly modified presternum 

 is unknown; such a feature occurs in no other Tachinidae. Another very unusual 

 character among Tachinidae that occurs in many Ormiini is the reduction of the 

 ocelli, some genera having the ocelli vestigial or totally wanting; all the ormiines 

 so far known in the Australasian fauna and in the African fauna are without ocelli. 

 In the Oriental fauna the genera Homotrixa Villeneuve and Xanthooestrus Villeneuve 

 possess ocelli, but in these genera the prosternal membrane is only moderately 

 inflated (Homotrixa) or not noticeably inflated at all (Xanthooestrus) and it is not 

 certain that the genera truly belong in the Ormiini. 



The existence of forms such as Xanthooestrus, which has an entirely ormiine 

 facies but has a normal presternum, and of forms such as Glaurocara, which has 

 a different morphological appearance yet has a perfect planidium larva and host 

 relations like the Ormiini, poses the question of whether the Ormiini ought to be 

 redefined on a much wider basis than at present. It appears now that a definition 

 of the Ormiini to include only those forms with inflated prosternal membrane is 

 too restrictive, and that several forms placed outside the group at present should 

 be brought into it. At present, however, insufficient is known of these generally 

 rather rare forms to permit any worthwhile re-evaluation of the Ormiini on a world 

 basis, and the Ormiini is here accepted in its usual confined sense with the 

 Glaurocarini recognized as a separate (rather intangibly defined) tribe. 



The main characteristics of the Ormiini are as follows. Eyes very large, bare, facets 

 conspicuously enlarged in most males; head of <$ usually holoptic or almost so, $ frons 

 therefore virtually absent; ocelli present or absent, when present often strongly raised in $; 

 inner vertical setae absent in male, usually present and converging or crossed in Cj; proclinate 

 orbital setae absent in <$• weak in $; parafacials bare; epistome not projecting, invisible in 

 profile, often formed into a receding strip which curves for a long distance between a reduced 

 face and the oral cavity; oral cavity, proboscis and palpi often exceptionally reduced; vibrissae 

 present or absent, when absent lower ends of facialia usually formed into broad haired areas 

 on each side of the epistomal strip; genal dilation weak or virtually absent; occipital region 



