Nineteenth Annual Meeting. 123 



more elongated, the basal and anal cells small, the third longitudinal vein simple, 

 not furcated, and only one submarginal and three posterior cells are present. Do 

 not confound the obliquely placed vein that nearly closes the first posterior cell with 

 the furcation of the third vein. The housefly will also show clearly the six longitudi- 

 nal veins, the last of which runs obliquely backward from the anal cell toward the 

 margin, the fifth bordering the discal cell behind, the first and second running into 

 the costa. The first vein that terminates in the costa ( before the middle of the 

 wing) is the auxiliary. The vein that closes the discal cell outwardly is the posterior 

 or great cross-vein; the one that closes the anal cell outwardly, the posterior basal 

 cross-vein. 



The above will indicate the leading principles of the neuration and structure 

 peculiar to flies. For further information, the reader is referred to the system of 

 terminology given by Loew in the first volume of the Monographs of North Ameri- 

 can Diptera, a system which, upon the whole, I believe to be superior to any other 

 now in use. 



The numerous sub-families of the Muscidce acalyptratce are omitted; I am not 

 able to include them satisfactorily. 



TABLE FOB THE DETEEMINATION OF THE FAMILIES OF DIPTEEA. 



1. Flies of a leathery or horny structure, living parasitically in the adult state upon 



warm-blooded vertebrates or bees; head small, either closely united to the 

 emarginate anterior part of the thorax, or folding back into a groove upon 

 the dorsum; mouth-parts incomplete, the palpi wanting; legs separated by the 

 broad sternum; abdomen indistinctly segmentated; claws well developed. . 49 

 Flies of softer structure, never living parasitically in the adult state upon warm- 

 blooded vertebrates; head separated from thorax by a free neck 2 



2. Antennae many-jointed, often longer than the thorax, the two basal joints, only, 



differentiated, the remaining joints usually distinct; palpi composed of from 

 three to five joints, usually elongate; anal cell never closed or narrowed at the 



margin *. {Nematocera.) 3 



Antennae rarely as long as the thorax, composed primarily of three joints, the 

 third of which may be simple or complex, (that is, composed of more or less 

 distinct annuli or segments,) with or without a terminal or dorsal arista or 

 style; anal cell closed before the border, or distinctly narrowed in the border, 

 or, if of other structure, the antennEe composed of three simple joints; palpi 

 rarely much elongate, composed of from one to three joints 12 



3. Dorsum of thorax with a distinct V-shaped suturet; wings (wanting in Chionea) 



many-veined, often with a complete discal cell; ocelli wanting (present in 



Trichocera) ; often large flies Tipulid^ 



Dorsum of thorax without a V-shaped suture, or rarely with any transverse suture 

 {Ble2)haroceridce) 4 



4. A complete discal cell present; ocelli present; empodia developed pulvilliform, 



pulvilli rudimentary Rhyphid^: 



No discal cell 5 



*Plecia, and perhaps some others, may be exceptions. 



iBittacomorpha, Ptychoptera, and Idioplasta will alone cause doubt here. They have the suture in- 

 completely V-shaped and sinuous. The last will be distinguished from Rhyphidw chiefly by the absence 

 of ocelli; the two former will be separated from the Culicida: by the absence of hair on the veins, their 

 larger size, and in Bittacomorpha by the peculiar clubbed tibiae. 



