62 R. W. CROSSKEY 



Tribe ORMIINI 



The Ormiini are parasites of crickets (Grylloidea) and bush-crickets (Tetti- 

 gonioidea), and the first instar larva is a planidium. The adult flies are characterized 

 by having the prosternal region conspicuously inflated, especially in the females in 

 which it usually forms an enormous balloon-like structure. The ocelli are often 

 completely wanting, and most ormiines have the oral cavity and mouthparts very 

 reduced (the epistome being much narrowed between widely expanded subfacials). 



Both Crosskey (19736) and Mesnil (19736) have provided preliminary definitions 

 of the group, and these agree upon restricting it to forms showing the inflated 

 prosternal region just mentioned. There are, however, several genera of aberrant 

 Tachinidae which greatly resemble the ormiines in having the oral cavity and 

 mouthparts very reduced and the subfacials greatly expanded (with consequent 

 reduction of the epistome to a narrow strip) but in which the prosternum is normal. 

 Such genera (which include, for example, Tachinoestrns and Zamimus) are difficult 

 to place, especially as their hosts and early stages are unknown, but it seems best 

 to omit them from the Ormiini; the tribe is then restricted solely to forms possessing 

 moderate to enormous inflation of the prosternum. (The function of the swollen 

 prosternum is unknown and offers an interesting field for speculation: in my view 

 it most probably acts as a sound receptor enabling these nocturnally active flies 

 to locate their night-singing grylloid and tettigonioid hosts.)* 



Specimens of Ormiini are uncommon in collections, perhaps because members 

 of the tribe are active at night, and the Oriental fauna is probably much richer 

 than is evident at present. Four genera are here recognized in the fauna, and these 

 deserve brief comment. Aulacephala appears to be mainly an African genus, 

 but is represented by at least one species in the Oriental area which ranges as far 

 as Japan: it is at once distinguished from other genera by the very long-petiolate 

 cell R 5 . The genus Homotrixa has not been seen (the type of the type-species 

 was, it is believed, destroyed with the loss of the Hungarian National Museum in 

 1956) but as interpreted by Townsend [Manual of Myiology) and Mesnil (19736) 

 is undoubtedly very similar to Phasioormia. It differs from Phasioormia by the 

 possession of ocelli, but it is questionable whether in the Ormiini (in which reduction 

 or total obliteration of ocelli occurs widely) this is to be regarded as a valid generic 

 character. Future revisionary work when more material is available will probably 

 show that no generic distinction can be maintained between Phasioormia and 

 Homotrixa and that the former should be treated as a synonym of the latter; 

 synonymy is not justified in the present state of knowledge and Phasioormia is 

 therefore treated as valid. 



The fourth genus is Therobia, which it is necessary to consider in more detail, 

 as Mesnil (19736) recognizes two genera in the Therobia-complex (namely Therobia 

 and Plesiooestrus) where I recognize only one. In an earlier paper (Crosskey, 

 19666 : 103) I proposed that five generic names in the Ormiini were new synonyms 

 of Therobia Brauer, namely Xystomima Villeneuve, Plesiooestrus Villeneuve, 

 Therobiopsis Townsend, Proxystomima Villeneuve, and Ormiominda Paramonov. 



* See Appendix, p. 337. 



