48 R. W. CROSSKEY 



A noteworthy difference between the Prosenini of the Orient and those of Australia 

 lies in the pteropleural seta. In the Oriental Region Prosena is the only genus 

 in which the pteropleural seta is absent (i.e. undifferentiated in the hair tuft on the 

 upper pteropleuron), all species in the other Oriental genera (such as Dexia, Billaea, 

 Philippodexia, Tylodexia) having at least one strongly developed upper pteropleural 

 seta. By contrast, the pteropleural seta is lacking in the Australian genera Senostoma 

 and Macropodexia (both close allies of Prosena) which form the faunal counterpart 

 in Australia of Dexia in the Oriental Region. 



Here may be mentioned the (apparently) disjunct distribution of the genus 

 Myostoma. This essentially Palaearctic genus occurs in the northern fringes of 

 the Oriental Region (northern India, Nepal, Sikkim) and also in northern Borneo 

 but is unknown from areas in between. 



Finally in this discussion of Prosenini it is necessary to call attention to the 

 synonymy of Prosena malayana Townsend with P. siberita (Fabricius) that is 

 newly established in the catalogue (Part II), and to an error in the statements 

 and figures that van Emden (1947) gave for these two nominal species. Van 

 Emden described P. brevirostris from the Ethiopian Region and at the end of 

 the description (van Emden, 1947 : 632) noted that this species differed from both 

 siberita and malayana in the male genitalia, and that these two species were also 

 different from each other. On plate II he illustrated (figs 13-15) the male terminalia 

 of what he considered to be the three distinct species. Unfortunately, examination 

 of the specimen and slide mount of genitalia in BMNH (correlated by a reference 

 number, 451) labelled by van Emden as 'malayana'' shows that the specimen he 

 used as the basis of his statements and figure for P. malayana was misidentified 

 by him: it is actually a hairy-parafacial specimen of Prosena belonging to P. facialis 

 Curran. Hence figure 15 on plate II of van Emden (1947) is of P. facialis, not of 

 P. malayana. 



From my own examination of a long series of Eurasian specimens of Prosena, 

 including the type-material of malayana (the type of siberita is lost) I can find nothing 

 either in external features or in male genitalia to suggest that malayana specimens 

 from south-east Asia are specifically distinct from the widespread northern Eurasian 

 siberita. On the taxonomic evidence available at present I therefore conclude 

 that malayana should be synonymized with siberita. 



Key to Oriental Genera of PROSENINI (DEXIINI) 



Proboscis short, its length much less than the height of the head. Pteropleural seta 

 distinctly differentiated. Palpi well developed, longer than the third antennal 

 segment ............. 2 



Proboscis very long and slender, its length conspicuously greater than the height of 

 the head (Text-fig. 28). Pteropleural seta absent. Palpi reduced, much shorter 

 than the third antennal segment. . . . PROSENA Le Peletier & Serville 



Abdomen with Ti + 2 excavate to its hind margin or almost so. Palpi normal, 



slender and filiform or at most slightly thickened apically, sometimes flattened . 3 



Abdomen with Ti + 2 not excavate for more than about half its length. Palpi 



very strongly clubbed DEXIO TRIX Villeneuve 



