J 50 



NORTH AMERICAN DIPTERA. 



posed cf four flattened leaves, two of them delicate 

 tracheal gills and the other two protecting chitinized 

 plates. The pupae are fastened by three pairs of pads on 

 the flat venter to the rock-bed or boulders in the swift 

 stream and are nonmobile. 



The delicate adults are to be found, usually only rare- 

 ly, despite the oft-time abundance of larvae and pupae, 

 clinging to rocks projecting from the stream or to stream- 

 side cliffs or foliage. The females are predaceous and 

 may be seen flitting about capturing small flies, especial- 

 ly Chirouomidae, which they lacerate with their saw-like 

 mandibles and knife-like maxillae in order to suck or lap 

 up the blood. The males are rarely found. A few spe- 

 cies are known as yet only in the larval and pupal stages. 

 The egg-laying habits are unknown. 



The family Blepharoceridae was established by Loew 

 in i860 to include a half dozen species, which could not 

 well be located in any of the existing families. Since 

 that time the number in the family has been increased to 

 about twenty known forms included in nine genera, of 

 which three genera, represented by eight species, are 

 found in the United States. Our species are recorded 



Fig. 47. Blepharoceridae. 1, Blepharocera, wing, showing second- 

 are venation (Comstock); 2. Paltosioma schineri, wing; 3, Phttorus, 

 wing (Kellogg); 4, Bibiocephata, wing (Kellogg). 



