AGEOMYZID^E. 103 



longitudinal vein; discal cell sometimes confluent with the 

 discal cell (Cryptochwtum, Aulacig aster), posterior cross-vein 

 sometimes wanting (Phytomyza) ; anal cell present; cross- veins 

 often much approximated (Agromyzinae). 



This family of small or minute flies, as here defined, includes 

 the Agromyzinae, Milichinee and Octhiphilinse of Schiner, the 

 Agromyzidae and Phytomyzidse of Loew. The group is 

 somewhat difficult to define in such a way that the novice will 

 always feel -sure of his determinations. From the Drosophi- 

 lidae (or at least the known American species) it will be dis- 

 tinguished by the non-plumose arista. From the Ephydridae, 

 Aulacigaster and Cryptochcettim will be distinguished by the 

 presence of a distinct anal cell. From the Geomyzidse it is 

 difficult to distinguish some of the genera, especially of the 

 Milichinae and Ochthiphilinae. The student would best con- 

 sult the table of that family in cases of doubt. Rhicnoessa 

 Loew is not included in the table : I can not define it. 



The larvae of Phytomyza are usually leaf miners. The lar- 

 vaes of Leucopis feed upon plant-lice ; those of Ochthiphila 

 have been found in the galls of Triticum repens. The larvae 

 of Ayromyza are elliptical in shape, the hind stigmata situated 

 upon small, rounded plates on the under side of the last seg- 

 ment; the abdomen is provided with false legs, without 

 bristles. The larvae of Leucopis are cylindrical, thicker pos- 

 teriorly, the skin roughened with short hairs ; hind stigmata 

 elongate, tube-like and widely separated; they creep leech- 

 like, or like the geometrid larvae. 



TABLE OF GENERA. 



1. Posterior cross-vein absent; oral vibrissae present (Phytomyzina). 



PHYTOMYZA Fallen. 

 Posterior cross- vein present. . . . . . . . 2 



2. Posterior cross-vein situated before the middle of the wing, the two 



cross-veins approximated. ... ... . . . 3 



Posterior cross-vein at or beyond the middle of the wing, the two cross- 

 veins not approximated ; arista bare. . .... . 7 



