394 PROCEEDENGS OF THE NATIONAL MUSEUM vol. io8 



Phytobia (Trilohomyza) varia (Melander) 



Agromyza varia Melander, Journ. New York Ent. Soc, vol. 21, p. 264, 1913. 



This species is typical of those in the subgenus Trilohomyza in 

 having yellow frons and femora. The head bears only one lower- 

 orbital (fig. 91) and is of a much different shape than that of Phytobia 

 (Trilohomyza) pleuralis (fig. 90). The dark area on the anepisternum 

 and the four strong dorsocentral setae also serve to separate P. (T.) 

 varia from P. (T.) pleuralis. The holotype and only known specimen 

 is from Idaho. 



5j. Subgenus Praspedomyza Hendel 



Praspedomyza Hendel, in Lindner, Die Fliegen der palaearktisclien Region, 

 fam. 59, p. 77, 1931. 



This subgenus is considered the most specialized because of the 

 form of the posterior spiracles of the larvae. Each is circular and 

 bears from 10 to 18 short bulbs. The adults are very similar to 

 those in the subgenus Trilohomyza but may be separated by the broad 

 prominent genovertical plates. These are distinctly above the plane 

 of the frontal vitta and are abruptly raised above it (fig. 92), The 

 adults are usually dark and may be distinguished from the dark 

 Phytobia (Trilohomyza) calyptrata by the aforementioned genovertical 

 plates. 



There are only two species in North America that belong to the 

 subgenus Praspedomyza sens. str. One, Phytobia (Praspedomyza) 

 morio, is Holarctic while Phytobia (Praspedomyza) subinjumata is 

 Nearctic. Phytobia (Praspedomyza) clara is included here only 

 because the posterior spiracles of the larvae each have 10 to 12 bulbs 

 arranged in a circle. The adults are yeUow and the gena is extremely 

 wide, being nearly two-thirds as high as the eye (fig. 93). The 

 Nearctic Phytobia clara and Palaearctic P. hilarella are very similar 

 species that are not closely related to other Phytobia species. The 

 larvae of both mine the fronds of Pteridium aquilinum (L.) Kuhn. 



Key to the described species of Phytobia (Praspedomyza) 



1. Frontal vitta brown or black; femora primarily brown 2 



Frontal vitta yellow; femora yellow clara 



2. Head with three or four lower-orbital setae; femora brown . . subinfumata 

 Head with two lower-orbital setae; femora brown except for forefemur being 



narrowly yellow distally morio 



Phytobia (Praspedomyza) clara (Melander) 



Agromyza clara Melander, Journ. New York Ent. Soc, vol. 21, p. 265, 1913. 

 Agromyza citreifrons Malloch, Ann. Ent. Soc. Amer., vol. 6, p. 290, 1913. 



This is a small (1.3 to 1.75 mm. in wing length) yellowish species 

 that contrasts strongly with the predominately dark species typical 



