114 NORTH AMERICAN DIPTERA. 



42. PSILID^E. 



Front bristly on the upper part ; broad. Face perpendicu- 

 lar or somewhat retreating in profile, without vibrissae. An- 

 tennae moderately or very long, decumbent. Abdomen rather 

 slender; male genitalia but little prominent, the oviduct 

 usually elongate. Wings large ; auxiliary vein absent ; third 

 and fourth longitudinal veins parallel ; all three basal cells 

 distinct. Legs elongate ; no preapical bristle on the tibiae. 



The flies of this family are of moderate size and elongate. 

 The larvae in those few species in which they are known live 

 in the roots or galls of different plants. The larvae of Psila 

 are slender, cylindrical, pale yellow, bare ; the posterior stig- 

 mata are small, rounded or button-like processes of a black 

 color. 



TABLE OF GENERA. 



1. Antennae much elongated, the third joint slender. LOXOCERA Meigen. 

 Antennas shorter than the face, the third joint oval or rounded. . 2 



2. Face nearly perpendicular in profile; anal cell noticeably shorter than 



the second basal cell. . . . . . . CHYLIZA Fallen. 



Face retreating in profile; anal cell as long or longer than the second 

 basal cell PSILA Meigen. 



43. ORTALID^E. 



Rather small to moderately large flies. Front broad in both 

 sexes, never with lower fron to-orbital bristles. Vibrissee want- 

 ing. Clypeus distinct, usually well developed ; proboscis 

 more or less stout; palpi broad, seldom narrow. Abdomen 

 with five segments in the male, six in the female, the first two 

 in both sexes more or less coalescent ; male with a rolled-up, 

 long penis ; female with a three-jointed, horny ovipositor. 

 Legs usually stout and short, never very slender. Venation 

 of wings complete ; auxiliary vein completely separated from 

 the first longitudinal vein, though often much approximated 

 to it ; it runs into the costa at a more or less acute angle, with- 

 out becoming indistinct at its end ; posterior basal and anal 



