UNITED STATES DEPARTMENT OF AGRICULTURE 



BULLETIN No. 779 



Contribution from the Bureau of Entomology 

 L. O. HOWARD, Chief 



Washington, D. C. 



PROFESSIONAL PAPER 



June 24, 1919 



THE GRAIN BUG/ 



By D. J. Caffkey and Geo. W. Baebek, 

 Scientific Assistants, Cereal and Forage Insect Investigations. 



CONTENTS. 



Introduction 1 



History 2 



Distribution 3 



Food plants 4 



Character of injury 4 



Description 6 



Life history and development 10 



Seasonal development 16 



Habits of nymphs 18 



Habits of adults 20 



Natural enemies 28 



Control methods 32 



Associated species of plant bugs 33 



Summary 33 



Literature cited 34 



INTRODUCTION. 



During the past few years the grain bug, (Pentatoma) Ghlorochroa 

 sayi Stal, has become a pest of considerable importance to the farm- 

 ers of the intermountain and southwestern States. It is now re- 

 garded as a serious menace to the growing of wheat and other small 

 grains in both the irrigated and nonirrigated districts within the 

 area of its distribution. 



The vital damage is caused by the piercing of the newly formed 

 heads of cereals and the feeding on the liquid contents, by which the 

 formation of the grain is prevented or its weight greatly reduced. 



The recent development of C. sayi as an economic pest is due to 

 an artificial change in its environment and food plants. This condi- 

 tion has been brought about by the cultivation of large areas formerly 

 devoted to grazing, w^hich practically eliminated many of the native 

 food plants and caused the insect to attack some of the crops grown in 

 its former habitat. The change to more succulent food plants, to- 

 gether with the better facilities for hibernation in the cultivated 

 areas, resulted in a marked increase of the pest. 



^ The observations detailed in this bulletin were made by the senior author in 1915 

 and by the junior author in 1916 during a destructive outbreak of the species in north- 

 eastern New Mexico and adjacent territory. The experiments were carried on at the 

 Field Laboratory of the Bureau of Entomology located at Maxwell, N. Mex. 



Mr. B. H. Gibson, of the Bureau of Entomology, kindly redescribed the adult of the 

 species and assisted in the preparation of notes on the history, synonymy, distribution, 

 food plants, and bibliography. 

 103881° — 19 1 



