174 



DIPTERA OF NORTH AMERICA. 



which often coalesce in the beginning of their coarse, forming a 

 more or less distinct fork. They have no ocelli, and the first joint 

 of their tarsi is much shortened. 



The second section, which Prof. Loew calls Anaretina, has one 

 longitudinal vein more, which is inserted between the second and 

 third veins of the first section ; this supplementary vein is simple 

 in Campylomyza and furcate in all the other genera. The first 

 tarsal joint is not shortened, and in all the genera, with the excep- 

 tion of Cecidogona, there are distinct ocelli. 



The first section, which contains all the gall-producing Cecido- 

 myidae at present known, comprises two genera of Meigen and a 

 third genus, discovered by Mr. Winnertz, and of which but a sin- 

 gle species is described. These three genera are easily distin- 

 guished by the nenration of their wings, which are always pubes- 

 cent, and may be characterized as follows : 



Cecidomyia Meig. Three or four longitudinal veins; in the first 

 case the third vein is forked, thus representing the third and fourth 

 veins, which are coalescent in the greater part of their extent (figs. 

 1, 2, and 4; in some rare cases a branch of this fork or the whole 



Fig. 1. 



Fig. 2. 



Cecidoiuyi 



Fig. 3. 



Colpodia. 



Fig. 5. 



Asynapta. 



fork becomes obsolete, as in fig. 3) ; 

 in the second case all the four veins 

 are simple (fig. 5). Surface of the 

 wings hairy ; margins with long cilia. 

 Antennae long, moniliform or cylin- 

 drical, generally verticillate, seldom 



without verticils, from 13 to 36-jointed. 



