240 



NORTH AMERICAN DIPTERA 



37. Bristles of the front normal except for the absence of the anterior 



pair of f rontals 38 



Bristles of the front differing in other ways 44 



38. A weak vein lies parallel with the costa beyond the third vein 39 



This vein absent 41 



39. First vein wholly bare 40 



First vein with one or two small bristles basally (20). 



Acontistoptera Brues 



40. Third and fourth weak veins very strongly cui-ved toward each other. 



Metopina Macquart 

 Third and fourth veins normal (1, 13) Pulicophora Dahl 



41. First vein present 42 



First vein absent (8, 9) Ecitomyia Brues 



42. Front with two pairs of post-antennal bristles 43 



Front with one pair of post-antennal bristles (17) Xanionotum Brues 



43. Post-antennal bristles of equal size Ecitophora Schmitz 



Post-antennal bristles of two sizes. . Ecitoptera Borgmeier and Schmitz 



PhoridjB IV. — 22. Coniceromyia vespertilio; 23, Gyinnophora verrucata; 24, Coniceraj 

 25, Diploneura; 26, Trineurocephala. 



