316 THE CANADIAN ENTOMOLOGIST 



4. Lateral margins of mesonotum concolorous with disc; pleurae 



entirely yellow. Food-plant unknown. 



Ill pleuralis Malloch. 



Lateral margins of mesonotum yellow; pleurae with dark 

 marks 5 



5. Very small species, 1 mm. in length; frons subquadrate; 



mesonotum with B pairs of dorso-centrals. Food-plant 



unknown. Wash clara Melander. 



Larger species, L5 mm. in length; frons longer than broad; 

 mesonotum with 4 pairs of dorso-centrals. Food-plant un- 

 known. Cal.; Maine citreifrons Malloch. 



6. Lateral margins of mesonotum pale yellow 7 



Lateral margins of mesonotum concolorous with disc 8 



7. Last section of fifth vein subequal to preceding section. Food- 



plant unknown. Alaska pollinosa Melander. 



Last section of fifth vein twice as long as preceding section. 

 Food-plant unknown. N. M indecisa Malloch. 



8. Legs entirely black ; frons reddish in front, blackish behind; 



thorax densely gray pruinescent, with 4 pairs of dorso- 

 centrals; outer cross-vein at its own length from inner. 

 Larvae mining in cambium of Amelanchier canadensis. 

 W. Va amelanchieris Greene. 



Legs with the knees at least pale, either reddish or yellow... 8a. 



8a. Large, robust species, at least 4 mm. in length; orbits poorly 



or not at all differentiated from interfrontalia; thorax with 



4 pairs of dorso-central bristles 8b, 



Smaller, slender species, at most 3 mm. in length; orbits well 

 differentiated from interfrontalia; thorax with 2, rarely 3, 



pairs of dorso-central bristles 9 



8b. Palpi reddish yellow; first costal division not over two-thirds 

 as long as second; last section of fifth vein subequal to 

 penultimate section. Larvae mining in cambium of 

 Betula niger. Col., Va.', Ill pruinosa Coquillett. 



Palpi black; first costal division about three-fourths as long 

 as second; last section of fifth vein distinctly longer than 

 penultimate section. LarvcX mining in cambium of Acer 

 ruhrum. Va aceris Greene. 



9. Last section of fifth vein 1 1/3 times as long as preceding sec- 



