396 PROCEEDINGS OF THE NATIONAL MUSEUM vol. io8 



Key to the subgenera of Cerodontha 



1. Third antennal segment distally bearing a spine or strongly projecting into a 



very acute angle; thorax and abdonien partially yellow. 6a. Cerodontha 



Third antennal segment with a blunt angle distally; thorax and abdomen 



shining brown or black 6b. Xenophytomyza 



6a. Svibgenus Cerodontha Rondani 



Cerodontha Rondani, Dipt. Ital. Prodr., vol. 4, p. 10, 1861. 



The adults placed in this subgenus are relatively slender and 

 elongate and the body is always partially yellow. The third antennal 

 segment either bears a spine or is produced distally into a very acute 

 angle. Crossvein m-m is always present. There are eight species 

 recognized in Europe but only one in North America. 



Cerodontha {Cerodontha) dorsalis (Loew) 



Odontocera dorsalis Loew, Berliner Ent. Zeitschr., vol. 7, p. 54, 1863 (Centuria 



III, No. 98). 

 Cerodontha dorsalis (Loew), Melander, Journ. New York Ent. Soc, vol. 21, p. 



249, 1913 (figure of head) (east of Rocky Mountains). — Aldrich, Ann. Ent. 



Soc. Amer., vol. 11, p. 63, 1918. 

 Cerodontha femoralis (Meigen), Melander, Journ. New York, Ent. Soc, vol. 21, 



p. 249, 1913 (Rocky Mountains, westward). 



The type is in the Museum of Comparative Zoology (No. 13433). 

 This species varies greatly in the proportions of yellow and black. 

 Aldrich (1918) showed that the dark western form came from the 

 region of cool nights and the more yellowish eastern form is from the 

 region of warm nights. Spring and fall collections, during seasons of 

 cool nights, produced the dark form in the east. Frick (1952) showed 

 that the male terminalia were the same for both color forms. The 

 mesonotum of the holotype female is illustrated to show the color 

 pattern (fig. 95). The larvae mine the leaves of many grasses, 

 pupating in the sheath. Cerodontha dorsalis is one of the most com- 

 mon and widespread species in the United States and Canada. 



6b. Subgenus Xenophytomyza Frey 



Xenophytomyza Frey, Notulae Ent., vol. 26, p. 51, 1946. — Frick, Kansas Ent. 

 Soc, vol. 25, p. 150, 1952 (figure of head). 



This subgenus contains three species, two Palaearctic and one 

 Nearctic. The adults are robust and shining brown or black. The 

 third antennal segment has a blunt angle distally in contrast to the 

 very acute angle of the species of Cerodontha sens. str. Crossvein 

 m-m is absent in one European species. 



