132 



University of California Publications. [Entomology 



The Psychodidffi are minute flies rather isolated from other 

 families. The venation is shown in Fig. 74. 



The Culicidse, Chironomidee, and Blepharoceridie constitute 

 a group with very little difference in venation; they are the 



FIG. 73. Venation of the Dexidic. 



FIG. 74. Venation of the Psycho- 

 dida?. Dotted line shows vein which is 

 often absent. 



nearest allies to the Psychodidae, their wings being somewhat 

 intermediate between the venation of that family and the nor- 

 mal type. (See Fig. 75.) 



FIG. 75. Diagram of venation of 

 Culieidfe, Chironomida;, and Blephar- 

 oceridse. Minimum venation is that 

 of Cliironomid.e: adding veins 

 marked B gives venation of Blephar- 

 oceridse. Tlie maximum venation is 

 that of Culicida'. 



FIG. 76. Diagram of venation of 

 liigher Nematocera. Maximum is 

 found in Rhyphida?; minimum in 

 Orphnephilida» ; Bibionidas and Simul- 

 id» are intermediate. Letters at end 

 of dotted lines indicate families in 

 which these veins are variable. 



The higher Nematocera exhibit but little variation in actual 

 venation, but vary greatly in the arrangement and relative 

 strength of the veins. The Bibionidas vary most in the former 



*=S. 



I 'FIG. 77. Diagram of venation of Bra- 

 chycera. Vein marked DC is wanting 

 in" Dolichopodida? and Lonchopteridw. 

 Brackets indicate tendency of union of 

 tips, and arrows direction of shifting. 



FIG. 78. Wing of Midan, show- 

 ing extreme of fusion and shifting. 

 In this case two anterior pair of 

 veins have become entirely fused. 



particular, and in the Simulidaj the independents and the 

 veins in front of them are strong, while the rest are reduced to 

 scarcely more than wrinkles of the membrane. (See Fig. 7<>.) 

 The Brachycera (Fig. 77) have a very uniform venation, but 

 several groups exhibit an evident tendency toward the 



