T^E NORTH AMERICAN SPECIES OF PARASITIC TWO- 

 WINGED FLIES BELONGING TO THE GENUS PHO- 

 ROCERA AND ALLIED GENERA. 



By J. M. Aldrich, 

 Associate Curator, Division of Insects, United States Nationul Museum. 



and 



Ray T. Webber, 



Of the Bureau of Entomology, United States Department of Agriculture. 



INTRODUCTION. 



The present paper is an attempt to classify a difficult group of 

 parasitic flies, species of which are very often reared in economic 

 work and sent to the United States National Museum for identifica- 

 tion. The only comprehensive work on the group hitherto pub- 

 lished was by the late D. W. Coquillett* ; he placed the species known 

 to him, 39 in number, in the genera Pharocera, Eupharocera, and 

 Exorista. The writers have excluded a few of his species, made 

 synonyms of a few, rearranged the genera to conform as conserva- 

 tively as possible with more recent ideas in nomenclature, and have 

 described 41 new species, while recognizing 40 previously described 

 North American species with a new description of each. 



The group of genera under discussion offers as a whole the fol- 

 lowing characters: 



Eyes hairy; ocellar bristles present and directed obliquely for- 

 ward; rows of frontal bristles extending downward at least to the 

 base of the third antennal joint ; antennae elongate, reaching at least 

 three-fourths of the distance from their origin to the edge of the 

 mouth; sides of face bare, at least on lower half; face receding; 

 vibrissae at or close to edge of mouth and not noticeably approxi- 

 mated to each other; palpi present and well developed; proboscis 

 short and fleshy. Thorax with well-developed chaetotaxy; anterior 

 acrostichals always distinct, one pair just in front of the suture ex- 



» Technical Bulletin No. 7, Division of Entomology, U. S. Department of Agriculture, 

 1897, pp. 91-105. 



No. 2486 — Proceedings U. S. National Museum, Vol. 63, Art. 17. 



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