No. 64] DIPTERA OF CONNECTICUT : TAXONOMY 167 



species this reduction has occurred by the coalescence of the first and 

 second branches of the sector (Eo and E-a), in others by the coalescence 

 of the third (E4) and fourth (E3) branches. 



Comstock believes the media (]M) has been reduced from its primi- 

 tive four-branched condition by the coalescence of the fourth branch 

 (M4) with either the third (M3) or the first cubitus (Cui). The 

 media never has four distinct branches in Diptera. A further reduc- 

 tion of the media maj'^ occur by coalescence of the first (Mi) and 

 second (M2) branches, by the coalescence of the third branch with 

 the first cubitus, or by atrophj^-. 



The cubitus (Cu) in many species is fused to a greater or less 

 extent with the second anal vein (2A). 



There are only two anal veins (lA and 2A), and the first of 

 these, when present, is usually represented by a very indistinct suture- 

 like vein just behind the cubitus. 



The cells of the wing, bounded by the veins, are named after 

 the vein bounding the cell anteriorly. The reduction in the number 

 of veins has obviously reduced the number of cells. Where two veins 

 coalesce, the cell behind the coalescence is named after the more 

 posterior of the two veins. 



The system of Comstock and Needham as above described has 

 been modified bj^ Tilly ard (see "Insects of Australia and New Zea- 

 land"). This author's basic scheme of dipterous venation differs 

 from the Comstock-Needham system in that the media is four- 

 branched, with consequent changes in the names given the posterior 

 veins. Thus Cui becomes M4, Cuo becomes Cui, lA becomes Cu2, 2A 

 becomes lA, and the somewhat evanescent vein in the axillary region 

 becomes 2A. The cell in the center of the wing, Comstock's first M^, 

 is called the median cell by Till^^ard. 



The wing of Tabanu^^ shown in Figure 17, illustrates the systems 

 of Loew (used in the Key to Families of the present work) and of 

 Tillyard. The terminology applied to the cells is sufficiently ex- 

 plained in the figure. This may be compared with the other wings 

 illustrated in Figures 15 to 17, where Tillyard's terminology is used. 

 The discal cell is Tillyard's median cell '(1st Mo in the Tipuloidea 

 of this volume). 



Further modifications of the terminology have been made for 

 the veins in the anterior part of the wing by Shannon and Bromley 

 (Insec. Inscit. Mens. 12: 137-140, 1924) and by Alexander (Trans. 

 4th Inter. Cong. Ent. 1928, vol. 2: 700-707). Shannon and Bromley 

 state that in certain Brachycera the first branch of the radial sector 

 is a branched vein, but the posterior of the two branches, E3, has 

 been deflected caudad and fused with E4 to form a vein E3+4. In 

 most Brachycera the basal connection is lost, but in some forms it is 

 represented by a complete transverse element or a spur. The vena- 

 tion of the xisilidae in the present work is given this interpretation. 

 Alexander has given another interpretation of the radial field, ac- 

 cording to which almost all higher groups of Diptera above the Tip- 



