BY FREDERICK A. A. SKUSE. 225 



misunderstanding of those really represented, the lost vein being 

 considered present. My theory of the venation in this family 

 differs almost entirely from that of Winnertz (as exemplified in 

 his monograph of the genus Ceratojyogon), but agrees principally 

 with those of Schiner (V.z-b. G. Wien, Bd. XIY. 1864) and Van 

 der Wulp (Tijd. v. Entom. XIY. 1871, p. 79-98). The latter 

 author bases his nomenclature on that of Schiner, and gives 

 (pp. 82-83) an elaborate table of the different terminologies of 

 Meigen (1), Macquart (2), Winnertz (2), and Schiner (2). In 

 the nomenclature employed by me I endeavour to follow Loew 

 and Osten-Sacken (Mon. Dipt. N. Amer.). 



On comparing the wings of Chironomus and Tanypus it is at 

 once evident that Winnertz's Wurzel- or Unterrandader (in Gera- 

 topogon) is composed really of the basal portion of the first longi- 

 tudinal and the whole of the second longitudinal ; in the former two 

 genera the second and third longitudinal veins take their origin, the 

 one from the other, at or beyond the middle of the first longitudinal, 

 and the presence of the marginal cross- vein and rudimentary 

 third longitudinal vein found in the wing of so many species of 

 Ceratopogon further testifies to the correctness of this veiw. Van 

 der Wulp regards the second longitudinal (his Radiaalader) as 

 wanting in Ceratopogon ; this vein, however, is plainly present, 

 and is called by him the Cubitaalader, really the correct name of 

 the rudimentary third longitudinal overlooked by him. The 

 second longitudinal and the marginal cross-vein are, however, 

 sometimes so reduced in Ceratopogon that they, in a few instances, 

 are known to amalgamate with, and form an incrassation of, the 

 tip of the first longitudinal. In Chironomus and Tanypus the 

 second longitudinal vein is often pale and sometimes entirely 

 wanting. The posterior branches of the fourth and fifth longi- 

 tudinal veins are named as distinct veins by Winnertz. 



The following table gives the nomenclature of the alar venation 

 in Ceratopogon as interpreted by Winnertz and V. d. Wulp, 

 compared with that substituted in the following pages, and will 

 assist in reading the descriptions of these authors : — 

 15 



