862 AN INTRODUCTION TO ENTOMOLOGY 



About one hundred species of the Agromyzidce as restricted here 

 have been described from our fauna. See monograph of the family 

 by Melander ('13 b). 



So far as is known the larvse of most members of this famil}^ feed 

 on Hving plants by forming burrows or mines in various parts of 

 them, but principally in the leaves. A common species, Phyiomyza 

 aquilegice, makes serpentine mines in the leaves of wild columbine. 

 Aquilegia canadensis. (Fig. 11 13). 



The family MILICHIID^ is a small group of flies that is often 

 classed with the Agromyzidee. The members of this family differ 

 from the agromyzids in that the costa is broken twice, once be- 

 yond the humeral cross-vein at which place there is usually a 

 stronger costal bristle, and again just before the end of vein Ri, and 

 the post vertical bristles are convergent. See monograph of this 

 family by Melander ('13 6). 



The family OCHTHIPHILID^ is also a small group of flies 

 which is often classed with the Agromyzidse. In this family the 

 oral vibrissas are wanting or not differentiated; the postvertical 

 bristles convergent, the subcostal vein ends in the costa; and the 

 clypeus is small. See monograph of the family by Melander 

 ('13 b). 



Only thirteen species, representing three genera, are recognized 

 by Melander from our fauna. 



Larvae of species of Leucopis prey upon aphids and upon coccids. 



This family is named the Chamsyidae by Hendel ('22). 



SUBSECTION II.— CALYPTRAT^ 



The Calyptrate Muscids 



To this subsection belong our most familiar representatives of the 

 muscid flies, of which the house-fly and the flesh-flies are good illus- 

 trations. In the families included here the alulas or clypteres are 

 well developed or of moderate size, not rudimentary ; the subcostal 

 vein is always distinct in its whole course ; vein Ri is never very short ; 

 there is a complete transverse suture on the thorax; the postalar 

 callus is present and separated by a distinct suture from the dorsum 

 of the thorax; and the abdominal spiracles, with but few exceptions, 

 are in the chitin. The flies are usually of moderate or considerable 

 size, never very small. 



The subsection Calyptratae includes a series of families that 

 are exceedingly difficult to differentiate. In fact no two of the author- 

 ities on this group of flies agree either as to the number of families 

 that should be recognized or as to the limits of certain families that 

 are generally recognized. This is believed to be due to the fact that 

 this group of flies is of recent origin and the different types included 

 in it have not become segregated by the dropping out of intermediate 

 forms. It is the dominant group of flies, including an immense num- 

 ber of species. 



