AFFINITIES OF THE DIPTEROUS FAMILY PHORID.K. 353 



can have phylogenetic import, I am inclined to doubt. I think 

 it can not be questioned that a complete venation is the primitive 

 condition for the Bibionidae, so that we cannot assume a common 

 origin for the Bibionidas and Phoridse on evidence from neuration, 

 but necessarily a Scafopsc-\\Vie or Apistcs-\\ke ancestor for the 

 Phoridae. This is manifestly improbable as it involves after the 

 fixation of a degenerating wing venation, vast strides in the evo- 

 lution of other organs (antenna;, palpi) to give rise to Phoridae 

 while the parent stock remains unchanged. 



Such a loss of posterior veins has occurred independently in 

 many groups ; the Stratiomyidae and Hippoboscidse may be men- 

 tioned among the Diptera and the Chalcididas, Proctotrypidae, 

 Bethylidae and Cynipidae among Hymenoptera. The adaptation 

 seems to be due to mechanical adjustment and of course not to 

 common ancestry. 



Palaeontology offers but little on the history of the Bibionidae 

 and practically nothing on that of Phoridae. The occurrence of 

 Phora has been recognized by Berendt ('45) and Loew ('50) in 

 Prussian amber. The bibionid genera Protoinyia, Bibio, Plcda, 

 and Bibiopsis have been found to occur together in considerable 

 abundance in the Mayencian formation at Radoboj in Croatia 

 (Heer, '47), while Scatopscis known first from the Ligurian, occur- 

 ring in Prussian amber with Plwra and also at Aix, France (Ser- 

 res, '29). 



In his monograph of the European Phoridae, Becker has ad- 

 vanced the idea that the Phoridae are derived from nemocerous 

 forms allied to the Mycetophilidae, basing his opinion principally 

 upon a careful comparison of the wing venation of the two families 

 made by Girschner. Girschner's view is given as follows : " Ich 

 halte das Phora Geader fur ein modificiertes Mycetophilidengea- 

 der, wie ich auch die Mycetophiliden fiirdie nachsten Verwandten 

 und Stammesangehorigen cler Phoriden halte. Ich deute das 

 Geader in der oben skizzierten Weise (reproduced here as Fig. 

 3). Von a bis b ist die Discoidalader mit der Cubitalader ver- 

 schmoltzen, wie dies schon angedeutet wird bei Macrocera. Bei 

 einigen Phora-Formen kann man ziemlich deutlich--doch nicht 

 so auffallend wie in der Zeichnung punctiert angegeben - - die 

 unter die Cubitalader hinstreichende Discoidalader wahrnehmen. 



