178 DIPTERA OF NORTH AMERICA. 



Fourth longitudinal vein forked ; antennae 11-20-jointecl ; % moni- 

 liform, pilose; joints pedicelled ; 9 submoniliform, joints sessile, 

 pubescent (fig. 11, wing). Campylomyza Meig. 



II. Ocelli wanting ; third longitudinal vein forked ; first longitudinal vein 



very short ; wings pubescent ; antennae % moniliforrn, verticillate ; 



9 submoniliform, pubescent. 



Antennae 16-jointed (fig. 12, wing). Lestremia Macq. 



Antennae 11-jointed. Cecidogona Lw. 



Fig. 8. 



Fig. 9. 



Campylomyza. 



Fig. 10. 



Lestremia. 



For further details as well as for the references, see Walker, Diptera 

 Britannica, Vol. Ill, which also contains beautiful figures of all the genera. 

 As to the new genus Tritozyga Lw., formed on an American species, Mr. 

 Loew thus characterizes it in a manuscript note of his : — 



" The whole structure of its body shows the nearest relation to 

 Campylomyza ; the form of the legs and wings is as in that genus; 

 the wings (Tab. I, fig. 13) have the same short pubescence and cilia, 

 and the three ocelli are just as distinct. The differences are the 

 following. 1. The vein, which in the second section of Cecidomyidce 

 is added to the number of the veins of the first section, is not 

 simple, but forked, in the new genus, and therefore approaches in 

 some measure the genus Anarete; 2. The very thick longitudinal 

 vein is not forked as in Campylomyza, but simple. The new genus 

 cannot be confounded with Anarete, the species of which have a 

 much more slender structure, a very elongated first joint of the tarsi 

 and the third longitudinal vein of the wing bipartite as far as the 

 base. From Lestremia and Cecidogona it differs in quite a similar 

 manner, and besides by the presence of ocelli, which are wanting 

 in both genera. The antennae are mutilated in the single specimen 

 which I have before me (a male from the District of Columbia), 

 therefore I can say nothing of the number of their joints ; their 



