380 PROCEEDINGS OF THE NATIONAL MUSEUM vol. los 



one-half brown or black." But I have had to consider the plane 

 of the lunule because of the very high lunule of Phytobia {Dizygomyza) 

 thompsoni; this lunule is in the plane of the frontal vitta and abruptly 

 raised above the mesofacial plate (fig. 83). The lunule in the sub- 

 genus Poemyza is m the plane of the mesofacial plate and is somewhat 

 sunken below the frontal vitta. The genovertical plates are broad, 

 rather sharply raised above the plane of the frontal vitta, and usually 

 widest immediately dorsal of the antennal base (fig. 78). The larvae 

 have three bulbs on each posterior spiracle (fig. 71). These are 

 variously modified and are usually strongly sclerotized. One or two 

 of the bulbs may be greatly elongate and acuminate. 



Of the six described species of this subgenus, four are Holarctic and 

 none is Neotropical. Phytobia (Poemyza) angulata and Phytobia 

 (Poemyza) subangulata belong to the scutellaris group that has the 

 prescutellar seta developed. The larvae of species whose life histories 

 are known mine the leaves of species in the plant family Cyperaceae. 

 Those without a prescutellar seta mine the leaves of species of 

 Gramineae. 



Phytobia atra has been deleted from the North American list. Frick 

 (1952) took the synonjony of Hendel (1931). A subsequent study of 

 the specimens showed that P. angulata of Melander is angulata sens, 

 str. and the angulata of Malloch (1931) is actually P. incisa. 



Key to the described species of Phytobia (Poemyza) 



1. Mesonotum with prescutellar seta present and developed 2 



Mesonotum with prescutellar seta absent or not differentiated 3 



2. Crossvein r-m beyond center of cell I-M2; m-m about its own length from r-m 



(fig. 77); forefemur distally yellow, others dark subangulata 



Crossvein r-m about at center of cell 1-Mj; m-m about 1.5 times its length 

 from r-m; all femora distally yellow angulata 



3. Femora distally dark or, if yellow, then for a distance subequal to the femoral 



diameter 4 



Femora distally yellow for one-third to one-half the femoral length . muscina 



4. Vein M3+4 with ultimate section about 1.5 times as long as penultimate; 



humerus and notopleural triangle dark 5 



Vein M3+4 with ultimate section subequal to penultimate; notopleural triangle 

 and part of humerus yellow lateralis 



5. Legs with all femora distally yellow inconspicua 



Legs with forefemur yellow, others dark incisa 



Phytobia {Poemyza) angulata (Loew) 



Agromyza angulata Loew, Berliner Ent. Zeitschr., vol. 13, p. 47, 1869 (Centuria 



viir, No. 87). 

 Agromyza neptis Loew, Berliner Ent. Zeitschr., vol. 13, p. 50, 1869 (Centuria 



vni. No. 93). 

 Dizygomyza semiposticata Hendel, in Lindner, Die Fliegen der palaearktischen 



Region, fam. 59, p. 49, 1931 (figures of head, wing, and puparial characters). 

 Agromyza cinereijrons Frost, Canadian Ent., vol. 63, p. 276, 1931. 



