886 Charles Paul Alexander 



The tibiae are black, with a broad white band beyond the base. The 

 second and third tarsal segments are pure white. The apically pubescent 

 wings (Plate XXX, 4) are characteristic of the genus. 



Family Rhyphidae 



The family Rhyphidae includes an apparently heterogeneous group 

 of three subfamilies which, until a very recent date, were placed in three 

 widely separated families of the nematocerous Diptera. The Rhyphidae 

 comprise about fifty species, arranged in some seven genera. The family 

 has long been held to contain only the genus Rhyphus and one or two 

 closely allied exotic genera. In 1916, Edwards (1916) removed the 

 genus Mj'cetobia from the family Mycetophilidae and placed it with the 

 Rhyphidae. A critical study of the immature stages of the genus 

 Trichocera now demonstrates that this group, likewise, should be placed 

 in very close proximity to the Rhyphinae. In general appearance the 

 three groups or subfamilies herein considered as comprising the Rhyphidae 

 differ greatly, but the larvae of all members are so unmistakably related 

 that there can be no question of the close phylogenetic relationship. 



The Trichocerinae have the more generalized wing venation, there 

 being three branches to the sector and three to the media, and two 

 distinct anal veins. The local species of Trichocera have the m-cu cross- 

 vein punctiform or obliterated by a slight fusion of Cui on M3. 

 Trichocera trichoptera O. S., of the Western States, has the cross-vein 

 very long and conspicuous. The second anal vein is long and subsin- 

 uate in the subgenus Diazosma Bergr., but very short and recurved in 

 the typical subgenus, in T. trichoptera being very short and reduced and 

 narrowing the second anal cell. 



Edwards (1916) and Knab (1916) have recently shown the probable 

 evolution of Mycetobia from the more generalized Rhyphidae such as 

 Rhyphus and Olbiogaster. The most important venational feature to 

 be considered is the reduction of the media in the Mycetobiinae, but 

 two branches persisting in Mycetobia and the vein tending to be evanescent 

 in the Ethiopian genus Mesochria. Species of Olbiogaster in some cases 

 have the posterior branch of the media less strongly chitinized than 

 the anterior fork, and probably indicate the manner in which the vein 

 is reduced. An entirely comparable case is seen in the related family 

 Ptychopteridae (comparing Ptychoptera and Bittacomorpha) . In the 



