[Berliner Entomolog;. Zeitschrift Bd. XXVI. 1882. Heft IT.] 



On Professor Brauer's paper: 



Versuch einer Characteristik der Gattungen der 



Notacanthen. 1882. 



By C H. Osten Sacken. 



A comparative critical survey and a better definition of the genera 

 of the larger famih'es of the diptera is one of the most urgent wants 

 in the preseut condition of dipterology. The publication of Dr. Brauer's 

 work on the Notacantha was therefore hailed by me witli a feeling of 

 eager anticipation. Upon a rapid persual, I concluded to publish a 

 short Addendum to it, a few notices on some little kuown genera, 

 which I had seen in coUections. Bnt npon a closer study, I was sorry 

 to find, that my remarks gradually turned into criticisms, and that the 

 only alternative I had to choose from was either to preserve an absolute 

 silence, or to publish a detailed critical review. Upon reflection, I 

 determined to follow the latter course. 



The lamilies Stratiomyidae, Tabauidae, Xylophagidae, Acantho- 

 meridae and Leptidae form a natural group, which has several characters 

 in common: three pulvilli, total absence of macrochetae, and smooth 

 legs, deprived of those bristles and spines, that distinguish the Asilidae, 

 and, in a lesser degree, most of the Bombylidae and Therevidae. The 

 tibiae especially are smooth, and wheu we see the genus Rüppelia Wied. 

 figured vvith some bristles along the tibiae, we may conclude with a 

 high degree of probability, that this genus does not belong in the circle 

 of relationship in question. (Compare Note I). The femora are in some 

 rare cases spinöse (Subula), or dentate (Acanthomera). — The principal 

 families in that group are well-marked enough; but there are, alongside 

 of them, many forms of transition, so-called synthetic types, which 

 render the exact definition of the families very difficult, and still more 

 so, a linear arraugement. In preparing my Catalogue of N.-Am. Diptera 

 (1878), I followed the arrangement proposed by Loew in the Mono- 

 XXVI. Heft II. 24 



