PHYLOGENY OF THE NEMOCERA. 25! 



Group 5. Families with from three to five joints: Mydaidse, 

 Apioceridae, Asilidae, Therevidae, Bombylidae, Dolichopodidae, 

 Empidae. 



The Orphnephilidae (n, 12), Bibionidae (8-12), Leptinse (3-8) 

 and Scenopinidae (3) fill in gaps between the chief groups. But 

 it is obvious that the author was not dogmatic in the formulation 

 of these groups, as later it is stated (p. 330) that "the antennae, 

 taken separately, are only partial evidences of relationship. 

 They must be correlated with all other organs of the body, and 

 must harmonize with theories based upon other organs." Carry- 

 ing out this idea, and quite agreeing that no single character 

 can be relied upon, I have endeavored to test the validity of 

 these phyla by other structures, for the most part microscopic, 

 such as the eyes, the trophi, and the genitalia; and I have 

 embodied the results of my studies in a series of tables. 



These tables have been made to show the dominant characters 

 of the families; every large family has numerous exceptions and 

 specializations, as, for instance, the labium in the Dolichopodidae 

 is nearly always short, though we know that it is long in Orthochile, 

 and longer than normal in Gymnopterus. In speaking of domi- 

 nant characters I must guard myself by saying that my cabinet 

 of dissections is composed mostly of the commonest and most 

 widely distributed forms, selected where the material for dis- 

 section was most abundant; there is, hence, probably a margin 

 of error. 



The tabulated observations are mostly contained in four 

 papers previously published by myself: "The Mouth parts of the 

 Nemocera," 1904, with additions and corrections (1909), (Journal 

 of the Royal Microscopical Society); "The Genitalia of the Sexes 

 in Diptera" (Trans. Linn. Soc., London, 1906), and "The Struc- 

 ture of the Surface and the Sexual Characters of the Eyes of 

 Diptera" (Journal Queckett Club, 1909). Many additional facts 

 since observed have been incorporated in the tables. 



The following explanations will be necessary for a full com- 

 prehension of these tables. The trophi are fully analyzed. Their 

 most important parts, from the point of view of phylogeny, seem 

 to be the tracheae of the paraglossae, the mentum, the palpi, and 

 the pharyngeal pump. The tables of the genitalia give the 



