1891.J 35 



SUaaESTIONS TOWAEDS a better GROUPINa OF CERTAIN 

 FAMILIES OF THE ORDER DIPTERA. 



BY C. R. OSTEN SACKEN. 



Ever since the sub-division of the Order Diptera in Orfkorrhapha 

 and Cj/cIorrhapJin, introduced by Brauer, attempts have been made to 

 bring about some mode of arranging the families of Orthorrhapha into 

 smaller natural groups. These attempts, first made by Schiner and 

 afterwards developed by Brauer,* cannot be considered as successful. 

 The reason is (as far as the families are concerned which I intend to 

 discuss in this article) that these groupings were principally based 

 upon a character of subordinate value, taken from the wings, and on 

 another character of doubtful importance, borrowed from the larvae, 

 ■without sufficient regard for the organization and the affinities of the 

 images. I believe that a natural arrangement must be the result of 

 the study of those organs of the imago which are necessary for the 

 functions of external life, principally, therefore, of the organs of 

 orientation connected with the head (eyes and antennae), and in the 

 second line, of the organs of locomotion (legs and wings). 



To begin with the Nemocera, as soon as we apply this method 

 to them we discover a mode of grouping more satisfactory, it seems to 

 me, than those hitherto proposed. 



The bulk of the true Nemocera form a natural aggregation of 

 Jive large families, widely and, as far as known, rather evenly distri- 

 buted in all parts of the world {Cecidomyidce, Mycetophilidce, Culicidce, 

 CJiironomidce, and Tipiilidce), and a sixth, smaller family (^PsycTio- 

 didce).f The remaining Nemocera are represented by Jive small 

 families : the Sihionidee, SimulidcB, RhypJiidoB, BlepharoceridcB , and 

 Orphnephilidee, whose organization is widely different from that of the 

 true Nemocera, and whose geographical distribution is peculiar ; I 

 form of them an artificial group, the Nemocera anomala, which, like 

 the Limnohina anomala among the Tijyulidce, seems principally to con- 

 tain archaic forms, remains of bygone entomological horizons. 



* Schiner, in the Verh. Zool. Bot. Ges., 1864, p. 2U ; Brauer, in his Characteristic der 

 Hauptffrup]ieu, kc. (in the Deukschr. K. Akad. d. Wiss. Vienna, vol. xlii, p. 110) ; a short 

 synopsis of the same arrangement in (. c, vol. xliv, p. 98 ; a modified system, I. c, xlvii, p 11 ; 

 further developments in his Systematisch-Zoologische Studien (Sitzungsber. d. K. Akad. d. Wiss. 

 Vienna, 1835, pp. 237—413), and in the Verh. Zool. Bot. Ges., 1890, pp. 273—275). 



t Thfi still problematic Dir.a will, perhaps, form a seventh family. The discovery of exotic 

 forms may clear up its position. Hitherto, a single species has been described from China 

 (Thomson, Kug., Rcsai, and three species are mentioned as occurring in New South Wales, but 

 not yet described (Skuse, Trans. Austr. Ass. Adv. of Sc, 1890, p. .'J50). Thus, about 27 species in 

 all are known to exist (about 15 in Europe, and 8 in North America), save, of course, tlie possible 



