20 NORTH AMERICAN DII'TERA. 



habits of only a few are known ; one species, described by 

 Fritz Muller, from South America is said to be dimorphic in 

 the 9, one form being sanguisugous, the other mellisugons. 

 The larvae live in running water. The head has a pair of slen- 

 der antennae ; the cephalothorax and the following segments, 

 each with a conical process bearing a bunch of bristles ; pupa 

 flattened, inactive and free, enclosed in a semioval, shell-like 

 skin, the anterior end with horny erect breathing tubes. On 

 the under side the skin is soft and transparent, and provided 

 with three pairs of suckers by which the creature clings 

 most firmly. The flies are found dancing in the spray of 

 waterfalls, or resting upon the foliage near the margin of clear 

 running brooks. 



TABLE OF GENERA. 



1. An incomplete longitudinal vein running into the posterior margin. 2 

 No incomplete vein running into the posterior margin ; proboscis much 



elongated; hind tibia? with spurs; claws simple; eyes entire, not 

 bisected ( $). (Central and South America and West Indies.) 



PALTOSTOMA We Inner. 



2. Second longitudinal vein furcate 3 



Second longitudinal vein not furcate. . . ... . 4 



3. Origin of the anterior branch of the second vein coincident with the 



origin of the third vein; front tibia? curved in $ . 



BIRIOCEPHALA Osten Sacken. 



Origin of anterior branch of second vein more distal than the origin of 

 the third vein; front tibia? straight in the $. A<IATHON Roeder. 



4. E3'es holoptic, bisected by an unfaceted cross band or by a simple groove. 



BLKPIIAKOCKRA Mac-quart. 

 Eyes broadly dk'hoptie and not bisected. . . LIPOXKUKA Loew. 



4. CULICID.E. 



Slender flies, characterized by the projecting proboscis and 

 by the plumose antennae of the male. Head small, round; 

 eyes reniform ; ocelli wanting. Antennae thread-like, com- 

 posed of fifteen joints; the first joint thick, the following 

 joints small, round, and beset with whorls of hair, forming in 



