UNITED STATES DEPARTMENT OF AGRICULTURE 



BULLETIN No. 834 



Contribution from the Bureau of Entomology 

 L. O. HOWARD, Chief 



Washington, D. C. 



PROFESSIONAL PAPER 



May 19, 1920 



BLACK GRAIN-STEM SAWFLY OF EUROPE 1 IN 

 THE UNITED STATES. 



By A. B. Gahan, Entomological Assistant, Cereal and Forage Insect Investi- 

 gations. 



CONTENTS. 



Introduction 



History of discovery of the insect in 



America 



Common name of the species 



Distribution 



Old-World distribution 



Distribution in America 



Probable future distribution in 



America 



Food plants 



Food plants in Europe 



Food plants in America 



Page. 



Page. 

 Synonymy and description of Tra- 



chelus tabidus 7 



Adult g 



Overwintering larva 8 



Manner of work and probable life 



history 9 



Extent and character of injury 11 



Parasites 12 



Suggestions for control 12 



Literature cited 14 



INTRODUCTION. 



That another exotic insect with possibilities for damage to agricul- 

 ture has become established in America, that it is now quite widely 

 distributed, and that it has already begun to make itself felt was 

 brought to light during the summer of 1918. In view of its probable 

 future importance and the consequent desirability of learning as soon 

 as possible the facts about its distribution, food plants, and injuri- 

 ousness, it is deemed expedient to bring the matter to the notice of 

 entomologists and others through publication at this time of such 

 information as is at hand. 2 



1 Tracheitis tabidus (Fab.). 



2 The writer is indebted to Miss Margaret: Fagan, of the. Bureau of Entomology, for 

 compilation of the appended bibliography ; to Messrs. W. R. McConnell, P. R. Myers, and 

 W. J. Phillips, also of the Bureau of Entomology, for reared and collected material and 

 notes which were invaluable in establishing the identity and distribution of the insect ; 

 to Dr. J. Chester Bradley, of Cornell University, for larval material of Cephus pygmaeus 

 as well as useful suggestions regarding characters for separating the larva? ; and to 

 Messrs. S. A. Rohwer and Wm. Middleton for numerous helpful suggestions. 



148465°— 20— Bull. 834 1 



