65 



these, all, with the exception of P. barhata, Linn., and /'. ftdvifascia, 

 Walk., — both of which are found in Cape Colony anfl belong to 

 Diatomineura, Rond., sensu stricto (having hairy eyes and the first 

 posterior cell in tiie wings open), — belong either to Pangonia, 

 sensd stricto (in which the eyes are bare and the first posterior cell 

 closed), or to the subgenus Corizoneura, Rond., of the genus 

 Diatomineura, Rond., characterised by the eyes being bare and the 

 first posterior cell open : the species of Corizoneura occur chiefly 

 in South Africa. So far as it is possible to judge from the material 

 at present received by the Museum, species of Pangonia would 

 appear to be fairly common in Central, East, and South Africa 

 (where Westermann long ago observed that Pangonia was more 

 numerous than Tahanus), and rare in West Africa. It may be noted, 

 however, that P. ril'ppellii, Jaenn., and a new and allied species 

 have recently been met with in Northern Nigeria, while Surcouf 

 has founded the subgenus Subpangonia for a species described by him 

 from French Congo ; two specimens of a species apparently nearly 

 akin to the latter, and characterised by the possession of a relatively 

 short, thick, fleshy proboscis, with remarkably elongate labella, were 

 taken at Obuasi, Ashanti, in June, 1907, by Dr. W. M. Graham. 



The slender, elongate proboscis, which is characteristic of the 

 genus, varies greatly in length according to the species, from 2.5 mm. 

 in the case of the little South African Pangonia {Corizoneura) 

 directa, Walk., to 26 mm. (just over 1 inch) in the case of P. gulosa, 

 Wied. (Plate IV., fig. 29), and 39 mm. (or rather more than 1| inch) 

 in that of P. rostrata, L. ; in the two last-mentioned species, both 

 of which, like P. directa, occur in Cape Colony, the proboscis is 

 much longer than the body. If a number of specimens of any 

 species but one with a relatively short proboscis be examined, it 

 will generally be found that the proboscis varies in length in different 

 individuals. In a paper on Brasilian Tabanidaj, Dr. Lutz has 

 pointed out that this is due to the fact that the labium is protrusible 

 and retractile, the base, when the labium is retracted, being spirally 

 coiled within the buccal cavity ; f this condition is found in all 



t CI. Dr. Adolpho Lutz. " Reitraego zur Kenntniss dor hrasilianisehenTabnniden . " 

 Revista da Sociedade Scientifica de Sao I'aulo, No. 1, p. 24 (June, 1905). 



