374 PROCEEDINGS OF THE NATIONAL MUSEUM vol. los 



6. Presutural dorsocentral present 5a. Phytobia 



Presutural dorsocentral absent 5b. Nemorimyza 



7. Head with two upper-orbital setae reclinate; gena narrow (fig. 89), posteriorly 



not more than one-third of the eye height; if higher (fig. 93), then femora 



yellow 8 



Head usually with only one upper-orbital, or if two, then only dorsal one rec- 

 linate; gena wide (fig. 67), posteriorly about one-half of the eye height; 

 femora primarily dark 5d. Cephalomyza 



8. Mesonotum usually with one presutural and three postsutural dorsocentral setae, 



if with only three postsuturals, then anepisternum and femora yellow . . 9 

 Mesonotum with either only three postsutural dorsocentrals or with four post- 

 sutural and none to three presuturals; anepisternum and femora mostly 

 black 5h. Calycomyza 



9. Genovertical plates at most slightly raised above the frontal vitta, usually in 



the plane of the frontal vitta (fig. 88) 5i. Trilobomyza 



Genovertical plates very abruptly raised above the frontal vitta, distinctly 

 above the plane of the frontal vitta (fig. 92) 5j. Praspedomyza 



5a. Subgenus Phytobia Lioy 



Phytobia Lioy, Atti 1st. Veneto, ser, 3, vol. 9, p. 1313, 1864. 

 Dendromyza Hendel, in Lindner, Die Fliegen der palaearktischen Region, fam. 59, 

 p. 22, 1931. 



This is considered a generalized subgenus, based upon adult mor- 

 phology. There is usually more than one intraalar seta, a well devel- 

 oped prescutellar, usually one or more posterolateral setae medially 

 on the mid tibia, and vein K4+5 ends closest to the wing tip (fig. 60). 

 There are usually four well-developed dorsocentrals but Kangas (1955) 

 has found species in Europe with only two or three, one always being 

 presutural. The flies are large and the wing length ranges from 2.5 

 to 5.0 mm. The larvae mine in the cambium of various woody plants. 

 The larvae are highly specialized and vary from 15 to 30 mm. in 

 length and up to 1 mm. in diameter when full grown. The posterior 

 spiracles each consist of three short bulbs. 



This subgenus is well represented in North America. Only two of 

 the species are Neotropical and are very unusual in that P. kallima 

 has brown markings on the wing (fig. 60) and the other, P. picta, has 

 the scutellam and mesonotal margins yellow. Of the Nearctic species, 

 P. waltoni is unusual in lacking medial setae on the midtibia. 



Key to the described species of Phytobia (Phytobia) 



1. Scutellum concolorous with mesonotum, black or heavily gray pollinose . . 2 

 Scutellum and margin of mesonotum yellow, central part of mesonotum dull 



black (fig. 61) picta 



2. Wing without brown markings 3 



Wing with brown markings (fig. 60) kallima 



3. Costa reaching to the end of R4+5, or slightly beyond 4 



Costa reaching to the end of M1+2 5 



