54 NORTH AMERICAN DIFTKRA. 



OSTEN SACKEN'S CLASSIFICATION. 

 Osten Sacken has offered many pertinent criticisms of 

 Brauer's classification, insisting that the Nemocera and 

 Brachycera are divisions of more fundamental importance 

 than was assigned to them by Braner. His classification, 

 so far as it was developed by him, is as follows: 



Suborder Orthorrhapha Nematocera. Palpi usually four or five-jointed, 



pendulous and more or less filiform. Antennae many jointed | more 



than six-jointed), usually filiform (seldom pectinate), with the 



majority of the joints of the flagellum homologous (homomor- 



phous) . 



Superfamily Nemocera Vera. Males dichoptic;* no bisection or 



bicoloration of the eyes. Antennae provided with sensitive hairs 



arranged symmetrically on the flagellum in verticils or pencils 



(except Mycetophilidae). No pulvilli;! empodia often, but 



not always present. 



A. Larvae peripneustic,} always terrestrial. Cecidomyidae, My- 

 cetophilidse. 



B. Larvae peripneustic or amphipneustic, aquatic, subaquatic, 

 sometimes terrestrial. Culicidae, Chirouomiike, Psychodidae, 

 Dixidae, Tipulidae. 



Superfamily Nemocera Anomala. Diptera with homologous (ho- 

 momorphous) joints to the flagellum; usually four-jointed palpi. 

 Males frequently holoptic, sometimes the females also. Pulvilli 

 usually present. Antennas without sensitive hairs. Ocelli usually 

 present. Bibionidae, Simulidse, Blepharoceridae. Rhyphidae, 

 Orphnephilidae. 

 Suborder Orthorrhapha Brachycera. Palpi not more than two-jointed, 

 not pendulous, the end joint more or less clavate. and larger than 

 the basal one; joints of the antennal flagellum, with rare excep- 

 tions, not homologous. 

 Superfamily Eremochaeta. No macrochaetae. Three well developed 

 pulvilli. Males predominately holoptic, the eyes often bisected. 

 Antennal fkigclluin polymorphous. Axillary incision, alula and 

 antitegula in most cases distinctly developed. I fiscal cell usnal- 



Thev are sometimes truly holoptic. 



fRecent investigations show that true pulvilli are sometimes present. 

 Xmphipneustic larvse are those in which the spiracles are con- 

 fined to the first and last segments: melapneustic those in which they 

 are confined to the posterior segments; peripneustic those in which 

 they are present on the median rings. 



